Ben Nevis
You are of course free to ask VW customer service yourself if you have any doubt - just as I did. Then make your own decision.
Billywizz
VIP Member
No I can’t but I am not a crash investigator, all I was saying is for the sake of a few quid a year is it really worth saving money on!
Billywizz
VIP Member
Strange also that in the USA (land of litigation), manufacturers have actually removed the requirement to replace brake fluid on service schedules.
[/QUOTE]
And you’d trust the yanks
Billywizz
VIP Member
And you’d trust the yanks
[/QUOTE]
I think being a mechanic myself I’ll stick to changing mine on a regular basis.
WelshGas
Retired after 42 yrs and enjoying Life.
Super Poster
Lifetime VIP Member
| Temporary Brake Failure | ||
The phenomena of having a brake "pedal to the floor" experience is not confined to car chases in old B movies. Although it is not a situation that every motorist has experienced it is one that is certainly happening to more and more drivers. Any make or model of car or van with hydraulic brakes is capable of this type of failure but it is most commonly found on front wheel drive cars. The phenomena described can occur regardless of whether the vehicle has an Antilock Brake System (A.B.S.) or not, although front disc and rear drum or four wheel disc brake systems utilising diagonal split brake designs are most prone to this fault. Traditionally a "by-passing" master cylinder is blamed as the cause of "pedal to floor" problems but by far the greatest cause of this type of failure can be attributed to Glycol based (normal) brake fluid that has been contaminated by moisture, the higher the moisture content the lower the fluid boiling point can become. A feature of brake fluid not commonly recognised is that it deteriorates over time. The main reason for deterioration is that brake fluid is hygroscopic, that is, it absorbs moisture from the air. Because of the heat produced by friction when brakes are operated, brake fluid is designed to have a high boiling point, typically about 265°C / 509°F. Any moisture absorption could find this temperature reduced to a mere 140°C / 284°F over a period of two years. At this level, any period of sustained braking could produce enough friction to bring the fluid to the boil, where it vapourises, leaving the driver with little or no brakes. Unlike engine oil which should be changed according to the distance driven, brake fluid deteriorates not with distance but with time. It continues to absorb water even when the vehicle is stationery. Most vehicle manufacturers recommend regular brake fluid changes on a time basis, e.g. every year. Unfortunately, such recommendations are not always followed and independent surveys have shown that many vehicles have dangerous brake fluid in them. | ||
| Causes of Abnormal Overheating | ||
Binding Brakes - Whether over adjusted or sticking brake parts including handbrake cables, calipers and wheel cyclinder pistons, also master cylinder valves sticking due to corrosion etc. causing residual pressure within the system. Operator Error - Examples of this are the parking brake not fully released or the driver resting his/her foot on the brake pedal. Brake Lining Material - The new type of non asbestos brake lining friction material allows greater dissipation of heat from either the disc or drum into the caliper pistons or brake cylinders. | ||
| Investigation - Post Accident | ||
The heat in the wheel cylinder / caliper is not immediately lost to atmosphere but is actually increased due to heat saturation from the greater heat in the disc or drum. The problem should still exist for at least 5 minutes and possibly up to 20 minutes dependant on conditions, immediate testing will prove ro disprove the driver's story. Another factor to be considered is that when a vehicle is stopped, after a period of sustained braking, then the journey continued heat transference can cause the brake fluid to boil. If the braking system has not been touched but left to cool until the vapourised fluid has condensed once again into liquid form, a very slight vacuum can occur within the system, to normalise the system would require the brake pedal to be depressed at least twice which causes a corresponding drop in the reservoir fluid level. However because of differing brake types this cannot be assumed to be the sole reason for disclaiming the fluid as a cause. Over-heated brakes have a distinct pungent acidic smell, therefore vehicles with drum brakes should be transferred to a building with restricted ventilation, when the rear drums are removed the odour will not only be obvious but it will also linger. In cases of moderate over-heating the brake drum, to the untrained eye will appear normal, correct examination of the inside of the drum will highlight the fact that it is polished smoothly and slightly dark blue on colour. The friction material will become darker and have a polished glazed appearance, any paint ot varnish on the shoe metalwork will be oxidised and appear dull with a blue tint. The utilisation of a small mirror and a source of light reflected onto the shaded friction material will enable a close examination of the lining surface to take place, under these conditions both the glazing and the effects of the bonding agent evaporation are more pronounced. When extreme over-heating occurs the disc pads will turn white at the edges, more so if the pad is not adjacent to a heat absorbing caliper piston. The varnish / paint on the steel backing of the disc pads will usually bubble or flake, except when they are not adjacent to the caliper piston, in that instance the steel backing will turn a dirty white or grey. The friction material touching the disc will be glazed though it can also develop a rough appearance as the material breaks down and transfers between the two. Extremely hot disc pad friction will have the appearance of black carbon crystal and the metal backs will appear pock-marked with fresh rust. The disc surface will be extremely rough and gouged with a fresh rust coating. Dust boots will be charred, the inside rubber seals will be degraded and leaking and the burning pads will leave a deposit of carbon soot. | ||
| Glossary | ||
Brake Fade - If brakes are used to the point of over-heating, the co-efficient of friction is reduced until virtually no friction or stopping power exists between the friction material (pads and shoes) and the discs or brake drums. The driver experiences a normal / high brake pedal but the vehicle will not decelerate at the expected rate no matter how hard the pedal is depressed. Vapour Lock - When the brakes are overheated the resultant heat transfers through the metal components of the wheel cylinder or caliper and boils the brake fluid. A gas vapour bubble is produced in the wheel cylinder or caliper displacing fluid back towards the master cylinder and the next depression of the brake pedal will allow the pedal to "go to the floor". Dry Boiling Point - This is the boiling point of the fluid when it is new and has negligible moisture absorption. Wet Boiling Point - This is the boiling point of the fluid after it has been exposed to moisture during a specified laboratory test, although most test houses merely add 3.5% water as the test is prolonged and finicky. Dual Brake Systems - These are usually split diagonally and are designed such that if a fault occurs only part (usually 50%) of the braking force is affected. Vapour lock in one brake will cause only partial brake loss, in these cases only one front brake would be operational and an inexperienced driver could easily cause an accident. | ||
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WelshGas
Retired after 42 yrs and enjoying Life.
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Part 1. https://www.aa1car.com/library/bfluid.htm
Why Change Brake Fluid?
by Larry Carley copyright 2019 AA1Car.com
Brake Fluid is a hot topic because most people don't know why it should be changed. Did you know the average motorist who drives 10,000 to 15,000 miles a year uses his brakes about 75,000 times a year? Did you know that nearly half of all motorists in a recent Car Care Council survey said brake failure was their number one fear amongst driving emergencies?
So consider this: After three years of service, the average boiling point of the brake fluid has dropped to a potentially dangerous level because of moisture contamination and may not meet minimum federal requirements for brake fluid.
Probably half of all cars and light trucks that are 10 or more years old in the U.S. have never had their brake fluid changed. Yet in many European countries, regular brake fluid checks are required, and half of all cars routinely fail such tests. That's a good case for changing brake fluid.
Brake fluid is stored in the master brake cylinder reservoir. The reservoir is usually a translucent plastic container on top of the master cylinder. This allows you to see the fluid level inside without having to remove the filler cap. Opening the cap unnecessarily should be avoided because it allows moist air to enter the reservoir, and moisture is not good for brake fluid.
CHECK BRAKE FLUID LEVEL
Brake fluid is one of the most neglected fluid in vehicles today, yet is vitally important for safe driving. Consequently, you should check the fluid level regularly. The level will gradually drop as the brake pads wear, but a sudden drop in the fluid level usually means there is a leak in your brake system. The fluid level should be maintained between the ADD and FULL marks, or the MIN and MAX marks. If the level is low, add the type of fluid specified on the filler cap (DOT 3 or 4).
BRAKE FLUID PREVENTIVE MAINTENANCE
Many experts have long recommend changing the brake fluid every year or two for preventative maintenance. Their rationale is based on the fact that glycol-based brake fluid starts to absorb moisture from the moment it is put in the system. The fluid attracts moisture through microscopic pores in rubber hoses, past seals and exposure to the air. The problem is obviously worse in wet climates where humidity is high.
After only a year of service, the brake fluid in the average vehicle may contain as much as two percent water. After 18 months, the level of contamination can be as high as three percent. And after several years of service, it is not unusual to find brake fluid that contains as much as seven to eight percent water.
An NHTSA survey found that the brake fluid in 20% of 1,720 vehicles sampled contained 5% or more water!
As the concentration of moisture increases, it causes a sharp drop in the fluid's boiling temperature. Brand new DOT 3 brake fluid must have a dry (no moisture) boiling point of at least 401 degrees F, and a wet (moisture-saturated) boiling point of no less than 284 degrees. Most new DOT 3 fluids exceed these requirements and have a dry boiling point that ranges from 460 degrees up to over 500 degrees.
Only one percent water in the fluid can lower the boiling point of a typical DOT 3 fluid to 369 degrees. Two percent water can push the boiling point down to around 320 degrees, and three percent will take it all the way down to 293 degrees, which is getting dangerously close to the minimum DOT and OEM requirements.
DOT 4 fluid, which has a higher minimum boiling temperature requirement (446 degrees F dry and 311 degrees wet) soaks up moisture at a slower rate but suffers an even sharper drop in boiling temperature as moisture accumulates. Three percent water will lower the boiling point as much as 50%!
Considering the fact that today's front-wheel drive brake systems with semi-metallic linings run significantly hotter than their rear-wheel drive counterparts, high brake temperatures require fluid that can take the heat. But as we said earlier, the brake fluid in many of today's vehicles cannot because it is old and full of moisture.
Water contamination increases the danger of brake failure because vapor pockets can form if the fluid gets too hot. Vapor displaces fluid and is compressible, so when the brakes are applied the pedal may go all the way to the floor without applying the brakes!
In addition to the safety issue, water-laden brake fluid promotes corrosion and pitting in caliper pistons and bores, wheel cylinders, master cylinders, steel brake lines and ABS modulators.
FLUID RELATED BRAKE FAILURES
From time to time we hear about reports of "unexplained" brake failures that caused accidents. When the vehicle's brakes are inspected, no apparent mechanical fault can be found. The fluid level is normal, the linings are within specifications, the hydraulics appear to be working normally and the pedal feels firm. Yet the brakes failed. Why? Because something made the brakes hot, which in turn overheated the fluid causing it to boil. The underlying cause often turns out to be a dragging rear parking brake that does not release. But that's another story.
The same kind of sudden brake failure due to fluid boil may occur in any driving situation that puts undue stress on the brakes: a sudden panic stop followed by another, mountain driving, towing a trailer, hard driving, etc.
A case in point: A child was killed in an accident when the five-year old minivan with 79,000 miles on it his parents were driving suffered loss of pedal and crashed while the family was driving in the mountains of Washington state. Fluid boil was blamed as the cause of the accident.
OEM BRAKE FLUID RECOMMENDATIONS
What do the auto makers say about fluid changes? General Motors and Chrysler do not mention brake fluid in their scheduled maintenance recommendations. A General Motors spokesman said Delco Supreme 11 DOT 3 brake fluid contains additives than many other brake fluids do not, so it is essentially a lifetime fluid. Starting in 1993, GM began using a new type of rubber brake hose with an EPM lining and outer jacketing that reduces moisture penetration by 50%. So GM does not consider fluid contamination to be a significant problem.
Ford, for a time, recommended fresh fluid every 36,000 miles or three years, and to replace the fluid each time the brake pads are changed. Currently, however, Ford specifies no specific time or mileage recommendation for changing the brake fluid.
As for Chrysler, the only recommendation they publish is to change the fluid every 24 months on their Sprinter van.
A number of import car makers do recommend brake fluid changes for preventive maintenance at specific time/mileage intervals:
Acura: 36 months
Audi: 24 months
BMW: 24 months, or when indicated by Service Inspection Indicator
Honda: 36 months
Jaguar: 24 months all models except 2009 XF (36 months)
Land Rover: 36 months
Lexus: 36 months or 30,000 miles, which ever comes first
Mercedes-Benz: 24 months
MINI 24 months
Saab: 48 months (all models except 9-7X)
Smart: 24 months or 20,000 miles, which ever comes first
Subaru: 30 months or 30,000 miles (normal service) or 15 months/15,000 miles (severe service)
Suzuki: 24 months or 30,000 miles, which ever comes first (Forenza & Reno), 60 months or 60,000 miles (Grand Vitara and SX4)
Volkswagen: 24 months (New Beetle, City Gold, City Jetta), 36 months (all other models except Routan)
Volvo: 24 months or 37,000 miles (Normal), or 12 months (severe service)
Source for fluid change recommendations: Vehicle Manufacturer service information & owners manuals
If motorists would only follow this simple advice to change their brake fluid periodically, they could greatly reduce the risks associated with moisture-contaminated brake fluid. You can extend the life of your brake system and likely save yourself a lot of money in the long run on brake repairs, especially if your vehicle is equipped with ABS (because ABS modulators are very expensive to replace!).
Why Change Brake Fluid?
by Larry Carley copyright 2019 AA1Car.com
Brake Fluid is a hot topic because most people don't know why it should be changed. Did you know the average motorist who drives 10,000 to 15,000 miles a year uses his brakes about 75,000 times a year? Did you know that nearly half of all motorists in a recent Car Care Council survey said brake failure was their number one fear amongst driving emergencies?
So consider this: After three years of service, the average boiling point of the brake fluid has dropped to a potentially dangerous level because of moisture contamination and may not meet minimum federal requirements for brake fluid.
Probably half of all cars and light trucks that are 10 or more years old in the U.S. have never had their brake fluid changed. Yet in many European countries, regular brake fluid checks are required, and half of all cars routinely fail such tests. That's a good case for changing brake fluid.
Brake fluid is stored in the master brake cylinder reservoir. The reservoir is usually a translucent plastic container on top of the master cylinder. This allows you to see the fluid level inside without having to remove the filler cap. Opening the cap unnecessarily should be avoided because it allows moist air to enter the reservoir, and moisture is not good for brake fluid.
CHECK BRAKE FLUID LEVEL
Brake fluid is one of the most neglected fluid in vehicles today, yet is vitally important for safe driving. Consequently, you should check the fluid level regularly. The level will gradually drop as the brake pads wear, but a sudden drop in the fluid level usually means there is a leak in your brake system. The fluid level should be maintained between the ADD and FULL marks, or the MIN and MAX marks. If the level is low, add the type of fluid specified on the filler cap (DOT 3 or 4).
BRAKE FLUID PREVENTIVE MAINTENANCE
Many experts have long recommend changing the brake fluid every year or two for preventative maintenance. Their rationale is based on the fact that glycol-based brake fluid starts to absorb moisture from the moment it is put in the system. The fluid attracts moisture through microscopic pores in rubber hoses, past seals and exposure to the air. The problem is obviously worse in wet climates where humidity is high.
After only a year of service, the brake fluid in the average vehicle may contain as much as two percent water. After 18 months, the level of contamination can be as high as three percent. And after several years of service, it is not unusual to find brake fluid that contains as much as seven to eight percent water.
An NHTSA survey found that the brake fluid in 20% of 1,720 vehicles sampled contained 5% or more water!
As the concentration of moisture increases, it causes a sharp drop in the fluid's boiling temperature. Brand new DOT 3 brake fluid must have a dry (no moisture) boiling point of at least 401 degrees F, and a wet (moisture-saturated) boiling point of no less than 284 degrees. Most new DOT 3 fluids exceed these requirements and have a dry boiling point that ranges from 460 degrees up to over 500 degrees.
Only one percent water in the fluid can lower the boiling point of a typical DOT 3 fluid to 369 degrees. Two percent water can push the boiling point down to around 320 degrees, and three percent will take it all the way down to 293 degrees, which is getting dangerously close to the minimum DOT and OEM requirements.
DOT 4 fluid, which has a higher minimum boiling temperature requirement (446 degrees F dry and 311 degrees wet) soaks up moisture at a slower rate but suffers an even sharper drop in boiling temperature as moisture accumulates. Three percent water will lower the boiling point as much as 50%!
Considering the fact that today's front-wheel drive brake systems with semi-metallic linings run significantly hotter than their rear-wheel drive counterparts, high brake temperatures require fluid that can take the heat. But as we said earlier, the brake fluid in many of today's vehicles cannot because it is old and full of moisture.
Water contamination increases the danger of brake failure because vapor pockets can form if the fluid gets too hot. Vapor displaces fluid and is compressible, so when the brakes are applied the pedal may go all the way to the floor without applying the brakes!
In addition to the safety issue, water-laden brake fluid promotes corrosion and pitting in caliper pistons and bores, wheel cylinders, master cylinders, steel brake lines and ABS modulators.
FLUID RELATED BRAKE FAILURES
From time to time we hear about reports of "unexplained" brake failures that caused accidents. When the vehicle's brakes are inspected, no apparent mechanical fault can be found. The fluid level is normal, the linings are within specifications, the hydraulics appear to be working normally and the pedal feels firm. Yet the brakes failed. Why? Because something made the brakes hot, which in turn overheated the fluid causing it to boil. The underlying cause often turns out to be a dragging rear parking brake that does not release. But that's another story.
The same kind of sudden brake failure due to fluid boil may occur in any driving situation that puts undue stress on the brakes: a sudden panic stop followed by another, mountain driving, towing a trailer, hard driving, etc.
A case in point: A child was killed in an accident when the five-year old minivan with 79,000 miles on it his parents were driving suffered loss of pedal and crashed while the family was driving in the mountains of Washington state. Fluid boil was blamed as the cause of the accident.
OEM BRAKE FLUID RECOMMENDATIONS
What do the auto makers say about fluid changes? General Motors and Chrysler do not mention brake fluid in their scheduled maintenance recommendations. A General Motors spokesman said Delco Supreme 11 DOT 3 brake fluid contains additives than many other brake fluids do not, so it is essentially a lifetime fluid. Starting in 1993, GM began using a new type of rubber brake hose with an EPM lining and outer jacketing that reduces moisture penetration by 50%. So GM does not consider fluid contamination to be a significant problem.
Ford, for a time, recommended fresh fluid every 36,000 miles or three years, and to replace the fluid each time the brake pads are changed. Currently, however, Ford specifies no specific time or mileage recommendation for changing the brake fluid.
As for Chrysler, the only recommendation they publish is to change the fluid every 24 months on their Sprinter van.
A number of import car makers do recommend brake fluid changes for preventive maintenance at specific time/mileage intervals:
Acura: 36 months
Audi: 24 months
BMW: 24 months, or when indicated by Service Inspection Indicator
Honda: 36 months
Jaguar: 24 months all models except 2009 XF (36 months)
Land Rover: 36 months
Lexus: 36 months or 30,000 miles, which ever comes first
Mercedes-Benz: 24 months
MINI 24 months
Saab: 48 months (all models except 9-7X)
Smart: 24 months or 20,000 miles, which ever comes first
Subaru: 30 months or 30,000 miles (normal service) or 15 months/15,000 miles (severe service)
Suzuki: 24 months or 30,000 miles, which ever comes first (Forenza & Reno), 60 months or 60,000 miles (Grand Vitara and SX4)
Volkswagen: 24 months (New Beetle, City Gold, City Jetta), 36 months (all other models except Routan)
Volvo: 24 months or 37,000 miles (Normal), or 12 months (severe service)
Source for fluid change recommendations: Vehicle Manufacturer service information & owners manuals
If motorists would only follow this simple advice to change their brake fluid periodically, they could greatly reduce the risks associated with moisture-contaminated brake fluid. You can extend the life of your brake system and likely save yourself a lot of money in the long run on brake repairs, especially if your vehicle is equipped with ABS (because ABS modulators are very expensive to replace!).
Why Change Brake Fluid?
www.aa1car.com
WelshGas
Retired after 42 yrs and enjoying Life.
Super Poster
Lifetime VIP Member
Part 2. https://www.aa1car.com/library/bfluid.htm
TESTING BRAKE FLUID
Since you can't tell how badly contaminated brake fluid is by its appearance alone (unless the fluid is full of rust or is muddy brown), the fluid should be tested unless you are changing it for preventive maintenance or as part of a brake job.
There are three ways to check the condition of the brake fluid:
CHANGE BRAKE FLUID
When the fluid is changed, use the type of brake fluid (DOT 3 or 4) specified by the vehicle manufacturer. The cap on the fluid reservoir will usually indicate what type of brake fluid is required. You can also find this information in your Owners Manual (look under brake fluid).
As any brake fluid supplier will tell you, brake fluid is NOT a generic product. Just because a fluid meets the minimum DOT 3 or DOT 4 specifications does not mean it can tolerate moisture or provide the same degree of corrosion protection as another brand of fluid. The wet and dry boiling points of any given brand of brake fluid will depend on the additives in the fluid. Dry boiling temperatures for commonly available DOT 3 brake fluids may range from just over 400 degrees up to 573 degrees F, which is quite a spread. Wet boiling temperatures for DOT 3 fluids don't vary as much, ranging from 284 to 313 degrees F. All of these brake fluids meet the minimum DOT requirements as well as OEM requirements, but obviously a fluid that has a higher dry and wet boiling temperature provides a greater margin of safety and heat resistance.
As for differences in DOT 4 brake fluids, advertised dry boiling temperatures can range from a low of 446 to a high of 646 degrees F depending on the brand. Wet boiling temperatures for DOT 4 fluids are typically in the 300 to 400 degree range, with some being over 430 degrees F. Again, there is quite a range in performance depending on the brand.
There are also high temperature glycol based DOT 5.1 brake fluids (not to be confused with DOT 5 which is silicone based). The dry boiling temperature rating for DOT 5.1 is 518� F or higher, and the wet boiling temperature rating is 375� F or higher. Some racing brake fluids exceed the dry boiling temperature rating, but may only meet the wet boiling temperature requirements for DOT 3 fluid (284 degrees).
If you want to see a detailed comparison of brake fluid performance specifications and prices by brand name, see this Brake Fluid Comparison Chart compiled by Matt Robertson. Matt researched the wet and dry boiling points for each brand listed, and even included the unit price and per ounce price so you can compare one brand of brake fluid to another.
So the next time you are inspecting or servicing your brakes, be sure to check the condition of the fluid as well as the fluid level in the master cylinder. If you add or change fluid, use type of fluid specified by the vehicle manufacturer (DOT 3 or 4) and use the highest quality fluid you can get. And above all, remember the benefits of changing the brake fluid for preventive maintenance
TESTING BRAKE FLUID
Since you can't tell how badly contaminated brake fluid is by its appearance alone (unless the fluid is full of rust or is muddy brown), the fluid should be tested unless you are changing it for preventive maintenance or as part of a brake job.
There are three ways to check the condition of the brake fluid:
- An optical refractometer will clearly show the amount of moisture in the brake fluid. A small drop of fluid is placed in the tester, then the tester is held up to a light to read the amount of contamination. This tester is extremely accurate and shows both the percent of moisture and the fluid's boiling point. A source for this type of tool is Misco or Reichert.
- . . . .
- Chemical test strips. A chemical test strips made by Acustrip Company Inc. and Phoenix Systemscan be used to test the condition of your brake fluid. The test strips change color to reveal the condition of the fluid. If the fluid tests "bad" or "borderline" you should change the fluid.
Acustrip makes two different types of test strips to check the pH of the fluid and moisture content. Phoenix Systems test strips check the level of copper in the fluid. When copper levels reach 100, it indicates the corrosion inhibitors in the fluid are low and that the remaining service life of the brake fluid is limited. If the copper level is 200 or higher, the corrosion inhibitors are worn out and the fluid needs to be changed now. - . . . . .
- Electronic brake fluid testers measure the fluid's boiling temperature. The test takes only about a minute and is quite accurate. If the fluid's boiling temperature is getting dangerously low, replacement is recommended to minimize the risks of pedal fade caused by fluid boil. Sources for electronic brake fluid testers include Alba Diagnostics, MISCO and OTC.
CHANGE BRAKE FLUID
As any brake fluid supplier will tell you, brake fluid is NOT a generic product. Just because a fluid meets the minimum DOT 3 or DOT 4 specifications does not mean it can tolerate moisture or provide the same degree of corrosion protection as another brand of fluid. The wet and dry boiling points of any given brand of brake fluid will depend on the additives in the fluid. Dry boiling temperatures for commonly available DOT 3 brake fluids may range from just over 400 degrees up to 573 degrees F, which is quite a spread. Wet boiling temperatures for DOT 3 fluids don't vary as much, ranging from 284 to 313 degrees F. All of these brake fluids meet the minimum DOT requirements as well as OEM requirements, but obviously a fluid that has a higher dry and wet boiling temperature provides a greater margin of safety and heat resistance.
As for differences in DOT 4 brake fluids, advertised dry boiling temperatures can range from a low of 446 to a high of 646 degrees F depending on the brand. Wet boiling temperatures for DOT 4 fluids are typically in the 300 to 400 degree range, with some being over 430 degrees F. Again, there is quite a range in performance depending on the brand.
There are also high temperature glycol based DOT 5.1 brake fluids (not to be confused with DOT 5 which is silicone based). The dry boiling temperature rating for DOT 5.1 is 518� F or higher, and the wet boiling temperature rating is 375� F or higher. Some racing brake fluids exceed the dry boiling temperature rating, but may only meet the wet boiling temperature requirements for DOT 3 fluid (284 degrees).
If you want to see a detailed comparison of brake fluid performance specifications and prices by brand name, see this Brake Fluid Comparison Chart compiled by Matt Robertson. Matt researched the wet and dry boiling points for each brand listed, and even included the unit price and per ounce price so you can compare one brand of brake fluid to another.
So the next time you are inspecting or servicing your brakes, be sure to check the condition of the fluid as well as the fluid level in the master cylinder. If you add or change fluid, use type of fluid specified by the vehicle manufacturer (DOT 3 or 4) and use the highest quality fluid you can get. And above all, remember the benefits of changing the brake fluid for preventive maintenance
Bellcrew
Top Poster
VIP Member
So if every vehicle manufacturer used the miracle stuff General Motors and Ford put in their brake reservoirs we would not have to go through this exercise.Part 2. https://www.aa1car.com/library/bfluid.htm
TESTING BRAKE FLUID
Since you can't tell how badly contaminated brake fluid is by its appearance alone (unless the fluid is full of rust or is muddy brown), the fluid should be tested unless you are changing it for preventive maintenance or as part of a brake job.
There are three ways to check the condition of the brake fluid:
.
- An optical refractometer will clearly show the amount of moisture in the brake fluid. A small drop of fluid is placed in the tester, then the tester is held up to a light to read the amount of contamination. This tester is extremely accurate and shows both the percent of moisture and the fluid's boiling point. A source for this type of tool is Misco or Reichert.
- Chemical test strips. A chemical test strips made by Acustrip Company Inc. and Phoenix Systemscan be used to test the condition of your brake fluid. The test strips change color to reveal the condition of the fluid. If the fluid tests "bad" or "borderline" you should change the fluid.
Acustrip makes two different types of test strips to check the pH of the fluid and moisture content. Phoenix Systems test strips check the level of copper in the fluid. When copper levels reach 100, it indicates the corrosion inhibitors in the fluid are low and that the remaining service life of the brake fluid is limited. If the copper level is 200 or higher, the corrosion inhibitors are worn out and the fluid needs to be changed now.
- Electronic brake fluid testers measure the fluid's boiling temperature. The test takes only about a minute and is quite accurate. If the fluid's boiling temperature is getting dangerously low, replacement is recommended to minimize the risks of pedal fade caused by fluid boil. Sources for electronic brake fluid testers include Alba Diagnostics, MISCO and OTC.
CHANGE BRAKE FLUID
When the fluid is changed, use the type of brake fluid (DOT 3 or 4) specified by the vehicle manufacturer. The cap on the fluid reservoir will usually indicate what type of brake fluid is required. You can also find this information in your Owners Manual (look under brake fluid).
As any brake fluid supplier will tell you, brake fluid is NOT a generic product. Just because a fluid meets the minimum DOT 3 or DOT 4 specifications does not mean it can tolerate moisture or provide the same degree of corrosion protection as another brand of fluid. The wet and dry boiling points of any given brand of brake fluid will depend on the additives in the fluid. Dry boiling temperatures for commonly available DOT 3 brake fluids may range from just over 400 degrees up to 573 degrees F, which is quite a spread. Wet boiling temperatures for DOT 3 fluids don't vary as much, ranging from 284 to 313 degrees F. All of these brake fluids meet the minimum DOT requirements as well as OEM requirements, but obviously a fluid that has a higher dry and wet boiling temperature provides a greater margin of safety and heat resistance.
As for differences in DOT 4 brake fluids, advertised dry boiling temperatures can range from a low of 446 to a high of 646 degrees F depending on the brand. Wet boiling temperatures for DOT 4 fluids are typically in the 300 to 400 degree range, with some being over 430 degrees F. Again, there is quite a range in performance depending on the brand.
There are also high temperature glycol based DOT 5.1 brake fluids (not to be confused with DOT 5 which is silicone based). The dry boiling temperature rating for DOT 5.1 is 518� F or higher, and the wet boiling temperature rating is 375� F or higher. Some racing brake fluids exceed the dry boiling temperature rating, but may only meet the wet boiling temperature requirements for DOT 3 fluid (284 degrees).
If you want to see a detailed comparison of brake fluid performance specifications and prices by brand name, see this Brake Fluid Comparison Chart compiled by Matt Robertson. Matt researched the wet and dry boiling points for each brand listed, and even included the unit price and per ounce price so you can compare one brand of brake fluid to another.
So the next time you are inspecting or servicing your brakes, be sure to check the condition of the fluid as well as the fluid level in the master cylinder. If you add or change fluid, use type of fluid specified by the vehicle manufacturer (DOT 3 or 4) and use the highest quality fluid you can get. And above all, remember the benefits of changing the brake fluid for preventive maintenance
As an alternative every MOT test centre/service department could check the moisture/additive level in the brake fluid, again avoiding unnecessary replacement by simply testing the fluid using easily obtainable devices.
But of course where is the ongoing profit in that.
WelshGas
Retired after 42 yrs and enjoying Life.
Super Poster
Lifetime VIP Member
Brake systems are designed for the different grades of brake fluid used. Testing is possible but it is no different to having a Sell by Date on Food or testing it before eating or throwing it away.
I wouldn't be at all surprised if you did test the fluid that low milage vehicles would have a larger water content than high milage vehicles.
Christine Kirk
Lifetime VIP Member
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Our 2019 Cali is just 6 weeks off 3years old and yesterday as we were driving back from Surrey the MFD announced that an inspection service is due in 21days time; it will be interesting to see if they mention changing the brake fluid or pollen filter. It is something we have always done with our vehicles, as the seals and pistons last longer, I'm concerned that in the three years the wheels have yet to be taken off by VW and the Pads have not been out to clean up the calipers.I have now done about 35K so it's high time to do this work.
As to the potential life of any car it just requires careful and timely servicing and sometimes this can be costly or seem unnecessary
Me with the "old" runabout ! Yes I have to get the man to polish it, but I drive it (most of the time)
As to the potential life of any car it just requires careful and timely servicing and sometimes this can be costly or seem unnecessary
Me with the "old" runabout ! Yes I have to get the man to polish it, but I drive it (most of the time)
andyinluton
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The only time Vw will take the pads out is to replace them. In fact that’s probably the first time they will take the wheels off.
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