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Overheating of a T5 2.5 TDi 174 after being serviced

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caligraphy

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My T5 has started doing a strange thing. It was absolutely fine than I just got it back from a service and it started running hotter than normal. The temp gauge is saying it's exceeding the normal 90degC for the first time ever. This happens when running hard uphill but its never done it before. There is no excess pressure in the coolant. Curiously it doesn't seem especially hot. I can open the expansion tank within 10 minutes with no bubbling or scalding. Just a little hiss.

My engine is the 174 2.5 TDi. I've heard talk of water pump impellers and head gaskets but not on these. These engines are reputedly bullet proof (I suspect VW only changed them to reduce the range they carried and meet Euro 5/6 requirements). Besides, the engine seems healthy. No faullt was found in the service. It has low miles and fuel economy varies from 40 MPG mixed cycle to 47 MPG highway cruising on average (6-7l/100km).

I'll take it back tomorrow to the place I had it serviced. I am concerned that they've slightly overfilled the oil from what I can see. I'll also need to check the coolant level when it's cold.

Has anyone seen a similar problem, especially happening suddenly after servicing `/
 
caligraphy said:
My T5 has started doing a strange thing. It was absolutely fine than I just got it back from a service and it started running hotter than normal. The temp gauge is saying it's exceeding the normal 90degC for the first time ever. This happens when running hard uphill but its never done it before. There is no excess pressure in the coolant. Curiously it doesn't seem especially hot. I can open the expansion tank within 10 minutes with no bubbling or scalding. Just a little hiss.

My engine is the 174 2.5 TDi. I've heard talk of water pump impellers and head gaskets but not on these. These engines are reputedly bullet proof (I suspect VW only changed them to reduce the range they carried and meet Euro 5/6 requirements). Besides, the engine seems healthy. No faullt was found in the service. It has low miles and fuel economy varies from 40 MPG mixed cycle to 47 MPG highway cruising on average (6-7l/100km).

I'll take it back tomorrow to the place I had it serviced. I am concerned that they've slightly overfilled the oil from what I can see. I'll also need to check the coolant level when it's cold.

Has anyone seen a similar problem, especially happening suddenly after servicing `/
Click to expand...
Coolant change and Airlock?
Is it actually over temperature or is it a faulty temperature probe?
Does it have an Electric Radiator fan? Is it working correctly?
 
johntowers46 said:
@caligraphy

Never had this problem with mine, i wish i could achieve 40/47mpg with my cali.
It has two cooling electric fans, are they both working?
Click to expand...

The fans seem to be working but now the water pump has been diagnosed as at fault. The plastic impeller eventually starts to slip around the steel axle on which it's mounted. Silly design. First symptoms are overheating under load. The engine burns more fuel the more it revs, thus the (mechanical) driven impeller in the pump should go faster to keep up. It doesn't, it slips, so it starts getting too hot.

The hardest bit was getting it to VW without overheating at all. Driving 50mph on the M25 in 6th with the heater on full did the trick. Now there's just the £500 fix from VW to look forward to. Apparently they recalled these on Touregs of similar years (2004-on) but Calis are commercial vehicles so the owners get no such special treatment.

1. Getting good fuel economy with a heavy vehicle is achieved by avoiding braking and acceleration. F=ma is the formula. Use a minimum force (F) by keeping the acceleration (a) small as mass (m) is already about 3 tonnes. Braking loses kinetic energy (1/2 x mass x velocity squared). Kinetic energy comes from conversion of chemical energy from fuel or from gravity, so don't lose it.

2. Diesels don't like to be revved. They like to lug along using their enormous amounts of torque.
 
Last edited by a moderator:
caligraphy said:
The fans seem to be working but now the water pump has been diagnosed as at fault. The plastic impeller eventually starts to slip around the steel axle on which it's mounted. Silly design. First symptoms are overheating under load. The engine burns more fuel the more it revs, thus the (mechanical) driven impeller in the pump should go faster to keep up. It doesn't, it slips, so it starts getting too hot.

The hardest bit was getting it to VW without overheating at all. Driving 50mph on the M25qq§§§§§§§§§§§§§§§§§§§§§§§§§§§§§§§§§§§§§§§§§§§§§§§§§§§§§§§§§§§ in 6th with the heater on full did the trick. Now there's just the £500 fix from VW to look forward to. Apparently they recalled these on Touregs of similar years (2004-on) but Calis are commercial vehicles so the owners get no such special treatment.

1. Getting good fuel economy with a heavy vehicle is achieved by avoiding braking and acceleration. F=ma is the formula. Use a minimum force (F) by keeping the acceleration (a) small as mass (m) is already about 3 tonnes. Braking loses kinetic energy (1/2 x mass x velocity squared). Kinetic energy comes from conversion of chemical energy from fuel or from gravity, so don't lose it.

2. Diesels don't like to be revved. They like to lug along using their enormous amounts of torque.
Click to expand...

Is this a DIY job?
 
Is this the cam chain engine?

This is why on all VW engines the water pump is changed at the same time as the cam belt. The pump is buried inside the engine only accessible when changing cam belts.

Not the best Design in the world!
 
johntowers46 said:
Thanks @Loz
Would this be for the AXD engine?
Click to expand...
Not sure, its the 2.5 5 Cyl PD its longitudinally mounted in the Treg so the pump is close to the bulkhead.
I don't know much else to be honest just thought I would drop this in in case it helps. Ours was a V6, so totally different.

@Vw guru has probably done a few in his time??
 
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Emil Silenhag said:
That picture is engine code AXD/AXE and BNZ/BPC.
You dont nede to remove the gearbox. I’ve done 5 or 6 water pumps like this. Takes half a day first time and little faster next time. You need some special tools.
I’m written a “how to”, but in Norwegian/Swedish...interesting pictures so here is the link:
http://www.vwbus.no/forum/viewtopic.php?f=49&t=46541
Click to expand...

You're right. There is no cam belt or chain on the T5 2.5TDi. The camshaft is gear driven. Replacing the water pump takes 3-4 hours. My local garage didn't have the special tools so I had to pay VW labour rates. Still, cheers to Cordwallis at Heathrow for squeezing me in at a day's notice and their flawless customer service. The genuine VW pump costs around £140 so there was an all up cost of £500.

Designing a pump with a plastic impeller on a steel shaft for use in in a hot environment seems to be in keeping with VWs design philosophy of parts lasting just until the warranty expires. The unit that was removed had split and the impeller was barely able to grip the shaft. It would have slipped under high revs, which explains why the car could only be kept cool by keeping the engine under 2000rpm.

Given the cost of the labour it's worth buying the best quality replacement parts.
 
  • Agree
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Emil Silenhag said:
http://www.vwbus.no/forum/viewtopic.php?f=49&t=46541
Click to expand...

This is quite readable using Google Translate. It was reassuring to see VW no longer use plastic impellers though this is another example of design fault which should have been recalled for a free fix.

Sadly, after all the hassle my 2007 T5 California is now sold. I would not even consider buying a T6. VW have ruined the classic camper with their reliability problems. I regret ever selling my very high mileage 2001 LHD T4 California, which had all of the joys and fiunctionality of a modern T5/T6 California without the reliability issues.
 
caligraphy said:
I regret ever selling my very high mileage 2001 LHD T4 California, which had all of the joys and fiunctionality of a modern T5/T6 California without the reliability issues.
Click to expand...
:cheers
 
sidepod said:
Is this the cam chain engine?

This is why on all VW engines the water pump is changed at the same time as the cam belt. The pump is buried inside the engine only accessible when changing cam belts.

Not the best Design in the world!
Click to expand...
Everything is driven by gears on these engines, they are an odd design with the gears at the flywheel end and the alternator etc is driven by a coupling rather than a belt, the water pump is mounted in the block and needs a special tool to extract it, not looking forward to the day mine needs doing as I do not have £500.00 to give a garage so will have to find a way to do it myself.
 
Caligraphy … have the same motor, 08 reg, tiptronic box ... on 62k miles. What was your mileage on failure?
 
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