Thermostat replacement procedure on 2.0 Petrol ACC Engine

[Westie82]

Hi Guys,

Planning to install my new thermostat tomorrow as I'm having problems with my temp gauge which is under reading, has any one done a thermostat replacement on a Petrol 2.0 ACC ?

I have ordered a workshop manual, but it's not going to be here till the end of the week.

 

[TwentyOneThirtyFive]

Mines a diesel rather than an petrol, but the procedure will be similar.

Firstly some pictures

Here's a useful diagram, item 12 being the thermostat.

https://www.partsbase.org/vw/transporter-tr-eu-1993-12110-coolant-pump/

And here is the location on the engine, item 29 being the location I think.

https://www.partsbase.org/vw/transporter-tr-eu-1993-12145-coolant-hoses-and-pipes/


Procedure is pretty much the same, unbolt the plastic housing and get wet. At least, that is what I did. Have a bucket handy to catch the coolant, it can be reused.

Not sure how much coolant the petrol holds, the diesel holds more coolant than my bucket...

Change the stat (or test the current one, you can test them by dropping them into hot water).

Bolt the housing back on, taking care with the o-ring.

Pour coolant back in via the expansion tank. If it's not got the pink stuff (G12? at least) then consider replacing with new coolant.

Run the engine, ensure the heater is set to it's hottest setting. You can vent air from the system from a little plastic screw in a hose near the expansion tank.

Top up coolant as necessary and replace the lid on the expansion bottle before the water boils.

As an aside, my van reads 70c not 90c. It reads hotter when I go up hill and colder when I go down hill. The engine is running at 90c (fans coming on/off, wax stat opening vanes or rad appropriately. Infra red thermometer showing right water temp). I've tried changing senders, thermostat, radiator and radiator fan switch. Think it's likely an electrical problem. Or someone has fitted an altimeter.

dan

 

[Westie82]

Thanks for that Dan, just pondering if I should also change the 4 pin sender as well while i'm at it as I guess the sender can also cause temp gauge problems.

 

[TwentyOneThirtyFive]

Generally I prefer to change one thing at a time, but if you are in that area, will be a pain to have to deal with refilling the coolant twice.

Not sure if the petrol's are the same, but on the diesel I saw it recommended to change the sender housing at the same time as a sender, due to risk of leak afterwards. I didn't and got away with it, so don't know if it is a real risk or not.

 

[Westie82]

hmmmm, might just do the thermostat first and then see what happens, also been hearing about the early clocks suffering from cracked solder joints so I guess that could be another possibility which I might have to look into.

 

[TwentyOneThirtyFive]

I haven't had the courage to take the clocks apart yet. My understanding is that when the solder joints became an issue you lost both temp and fuel gauges?

 

[mrcheesbrough]

Hey Westie82. I think it's unlikely the thermostat will cause your temperature gauge to mis-read. It's job is simply to open and close as and when the engine requires cooling. The sender is the more likely culprit. My experience with the VW petrol engines is with a 1992 1.8, which I think is very similar to the 2.0 in your Westy. The housing had warped so needed replacing too when I did the thermostat. I think this is down to the petrol engine running a lot hotter than diesel. I'd probably change the sender first as it tells the gauge whats happening. It's also a lot simpler job with less coolant loss. Make sure you do it with a cold engine. The sender failed on our Westy not long after getting it - intermittent readouts. Had the sender changed and it's been fine ever since.

 

[mrcheesbrough]

I suspect if your thermostat was to blame the engine would be running very cool and you'd find the fuel economy through the roof as it would assume things were still cold. There's a way to check whether the thermostat works without removing it as certain coolant pipes will stay cold until the thermostat opens for the first time. I couldn't honestly tell you which one it would be but there's probably info somewhere online about it. If the thermostat was 'broken' open then all the pipes would warm at the same rate.

 

[mrcheesbrough]

On investigation I think the coolant pipe that stays cool should be the one from the radiator to the thermostat connection on the waterpump. As the radiator supplies cold water into the system when then thermostat opens. If the thermostat is permanently open then this pipe will warm at the same rate as all the other coolant pipes because the radiator isn't isolated from the system by the thermostat. A bit complicated to explain without being able to point at oily bits but hopefully it's a check you can perform before diving in and getting dirty water everywhere.

 

[Westie82]

Hello Mr Cheesbrough,I suppose it might be the Stat, the problem I am getting is that the temperature gauge never exceeds the mark as per the attached photo indicating the engine is running cool.

Last time I took her for a spin the needle didn't move from the rest until after 7 miles , the other day I did get a bit concerned as I took her on a long run and in a blink of an eye lid the red temp light came on and then off again but this only happened once and as I said only for about a second (the gauge at the time was still reading cool as per photo) I also checked the coolant and the level was perfectly fine

Dan, well that's reassuring to know about the soldering problem as my fuel gauge seems fine just the temp giving me grief.

Will test the pipe work tomorrow as mentioned above, hopefully that will rule in or out the thermostat.

 

[Westie82]

Hey Westie82. I think it's unlikely the thermostat will cause your temperature gauge to mis-read. It's job is simply to open and close as and when the engine requires cooling. The sender is the more likely culprit. My experience with the VW petrol engines is with a 1992 1.8, which I think is very similar to the 2.0 in your Westy. The housing had warped so needed replacing too when I did the thermostat. I think this is down to the petrol engine running a lot hotter than diesel. I'd probably change the sender first as it tells the gauge whats happening. It's also a lot simpler job with less coolant loss. Make sure you do it with a cold engine. The sender failed on our Westy not long after getting it - intermittent readouts. Had the sender changed and it's been fine ever since.

Seems like there are 2 senders, just to check ones a 2 pin which is for the coolant level and the 4 pin one is for the gauge?

 

[TwentyOneThirtyFive]

There's a sensor in the expansion tank for the coolant level, that's the one that usually triggers the red light.

Looking at this diagram, it shows the two senders, one for the gauge (item 7 - 4 pin) and one for a controller (item 5 - 2 pin). Does it have an ECU? I think the 2.5 does but don't know about the 2.0. If so, that will be the 2 pin sender.

https://www.partsbase.org/vw/transp...0-switches-and-senders-on-engine-and-gearbox/

Regarding slow to warm up, does the petrol have vanes on the radiator that open and close? It's common for the wax stat to seize, usually open resulting in slow warming up. Can be freed with a bit of wiggling and some lube. Might just be a diesel thing though as they are slower to warm.

Other things to check if none of this pans out - do you hear the fans coming on at all? Harder to check in the winter. Worth getting hold of an infrared thermometer as well, quite cheap on eBay. You can check the temp of hoses and the rad really easy then, see what the temp is and does it match the gauge.

 

[mrcheesbrough]

That sounds like a thermostat issue to me. If it was just the sender I would expect it to be a bit more intermittent in its reading rather than never getting up to temperature. That's what ours did before we had it changed. The gauge would read normal temperature sometimes then nothing at others. I think your initial plan to change the thermostat may well be the best place to start particularly if all the coolant pipes warm through at the same rate.

As for the senders one is for the gauge, the other for the ECU. I think the 4 pin is something to do with the circuit that allows the fan to run on once the engine is switched off. As Dan says the level sensor is in the expansion tank.

All just a time consuming process of elimination unfortunately. Keep us posted.

 

[Westie82]

That sounds like a thermostat issue to me. If it was just the sender I would expect it to be a bit more intermittent in its reading rather than never getting up to temperature. That's what ours did before we had it changed. The gauge would read normal temperature sometimes then nothing at others. I think your initial plan to change the thermostat may well be the best place to start particularly if all the coolant pipes warm through at the same rate.

As for the senders one is for the gauge, the other for the ECU. I think the 4 pin is something to do with the circuit that allows the fan to run on once the engine is switched off. As Dan says the level sensor is in the expansion tank.

All just a time consuming process of elimination unfortunately. Keep us posted.

Yes, I wouldn't describe it as erratic. It just hangs on the needle rest for about 7 miles then slowly goes up to the first division but never exceeds that point.

Well i'll have a feel of the pipes tomorrow to check if there is a difference in temp, how long will it take with the engine running for it to become apparent, would 5 mins be enough ?

 

[mrcheesbrough]

It's difficult to say how long exactly it should take to warm up. If the outside temperature stays in, or near double figures I'd reckon 10 minutes should be enough to get a sense of whether everything is warming up together or if the radiator remains isolated until there is a demand for cooler water in the system. You could probably speed things up a bit by increasing the revs from inside the engine bay.

 

[sidepod]

Once the old stat is out, pop it in a bot of boiling water and watch to see if it snaps open.. If it does, it's fine and your problem lies elsewhere..

 

[Westie82]

Ok Guys, the results after 20 minutes with the engine running …..

1. All pipes start to get warm fairly equally within 10 minutes with the exception of the Theremostat pipe which is cold.

2. 20 minute mark – with my hand on the Thermostat pipe I suddenly felt it warm then get hot quite quickly indicating thermostat operation (Needle position at this point is per first mark as per photo.

3. Fans didn’t come on at any stage? (Not sure if they supposed to)

So I guess from this test we can say that the thermostat is working correctly as they either fail open or closed from what I have read. So now thinking it might be the 4 pin sender ?

 

[TwentyOneThirtyFive]

Yep, changing the sender is what I'd do next.

Fans won't come on until water temp is 90 something c (thermostat opens at 87c), so wouldn't worry about that. only an issue if it is overheating.

 

[mrcheesbrough]

Hi Westie82. That seems pretty conclusive about the thermostat. I'm glad the cold pipe/warm pipe test worked. It could of been a lot more work if you'd removed the thermostat housing to discover it was warped. Fingers crossed the sensor is the culprit. A much easier job to perform. Make sure the coolant system is cold though as it will force its way out when you release the sensor from its mounting.

 

[Westie82]

Just rang VW £40 squid for the sender, one on the shelve so going to pick it up tomorrow. Bit weary of anything aftermarket, as the saying goes "buy cheap buy twice".

 

[Westie82]

Hi Guys,

With this nice Sunny weather I finally changed both the sensors (2 pin ECU and 4 Pin ) , surprised how easy it was and all done in just 20 mins!

Temperature gauge working fine now so happy boy !

Thanks for those who imputed into this thread.

 

[sidepod]

Good work. Photos?

 

[mrcheesbrough]

A productive 20 minutes. Glad to hear it's done the trick.

 

[Westie82]

 

[Westie82]

To help any other members which may come across the temp gauge problem the above photos shows the 2 sensors which are found on the 2.0 AAC engine. The 2 pin 025906041A is for the ECU and the 4 pin 701919369D controls the cooling fans and engine temperature gauge.

Obviously if your temp gauge is playing up don't forget to check the thermostat operation first as per Mr Chessbrough's earlier post in this thread, also the other known fault is the voltage regulator on the instrument cluster but from what I hear that effects both the fuel and temp gauge as per what Dan said. I also believe it causes erratic gauge reading due to the cracked soldered joints.

The procedure for changing the sensors is very simple, I had it done well within 30 mins.

1. Park on level ground make sure engine is not hot.
2. Drop the radiator forwards to allow more room to work (Remove 4 x 10mm bolts)
3. Unplug and remove the blue electrical connectors from the sensors.
4. Remove the horseshoe shaped retaining clip, this will allow you to remove the sensors. You will loose some coolant when you remove the sensors but I kept the cap on the expansion tank so it was very minimal.
5. Install the new sensors, I would recommend a new o-ring and retaining clip. Carefully push the sensors into the housing till they are fully home ensuring not to nick the o-rings . Reinstall retaining clips to both sensors.
6. Reconnect plugs.
7.Check coolant level, top up if necessary
8. Job done!

It may not be necessary to replace the 2 pin sensor but they are pretty cheap (£18.00 for a genuine one) so I thought I might as well do it whilst I was doing the 4 pin sensor. The 4 pin sensor is much more expensive at £38 from VW). You can of course get cheap generic ones (£12 off ebay) if you don't want to buy genuine VW.