2.0TDI temperature problems.

[LongValley]

Greetings all.
2010 build, Mk 6 Diesel. 147K on the clock
The car always ran at 90C on the gauge, no matter what. (Oil temperature moved around depending on work load).
A few weeks ago, the water temp would not come up, unless on a long hill climb @100kph. Aha, thermostat failure, I thought.
Just had the offending item replaced (the specialist, non-stealership service people now know that it is NOT a three-hour job!). However, this has not fixed the problem. Homeward trip, 25 km, 8 degrees ambient, engine temp up to 70 and down to <60, with a final oil temp of 58deg.

Any ideas? :face palm:

P.S. It's still the best car I've ever had - and I've had a few!!

[Umai Naa!!]

Water pump?

[Greg Roles]

Yeah, was it replaced at about 100k with the timing belt?

[wogboy_9000]

Can I ask how long it takes to come up to temperature (90 degrees)?

We have two Mk6 2.0 TDIs in the family. One has 120K takes 15-20 mins of outer urban driving to come up to temperature.

The other has 210K and I can't remember the last time I saw the gauge over 1/4 (to be fair, my trips are usually no longer than 15-20 mins). It's going in for a timing belt and water pump soon, so I'll report back and let everyone know if this changes anything.

The good news is that both the 120K and 210K golfs drive almost identically. The only difference is the 6 Speed DSG is slightly jerkier in the 210K. I've ordered a VCDS cable so I'll reset the gearbox when it arrives and see if it changes anything.

[Idle]

I drove a Mk6 TDI for about three years, from day one it took 15-20 minutes to reach its indicated 90 degrees (which, btw, isn't necessarily the actual working temp, just an indication that nothing's wrong.)

A sore point was that it took nearly as long to get anything useful from the heater.

Now have a Mk7 — it warms up much quicker (about 5K, and the heater blows warm air in less than 2.)

[harlie]

Are you sure the temp gauge is correct? I would start with a probe (my multimeter has this function) to ensure the sender and gauge are correct.

If it helps - I had this same issue with our other car (inline 6 3.0 BMW diesel). replaced thermostat, not fixed. Went looking through the workshop manual and noticed a thermostat in the EGR cooler which runs from one side of the engine stat to the other. It was stuck open causing the problem.

I don't have access to a good document on the VW engine, if the gauge is correct there must be another loop. The BMW has another thermostat in the transmission cooler that would provide a loop as well as the EGR cooler.

[Umai Naa!!]

Temp probe, even in the expansion bottle, will help.

The gauge is very slow to react, and being a diesel, they take forever to warm up anyway just idling away.

Also, when up to temperature with the cap on, after a few big revs, you should see coolant flow at the top outlet on the expansion bottle.

[bisy]

My GTD did the same There is 2 thermostats on the golf


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[bisy]

After replacing both thermostats it was back to normal


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[LongValley]

Thanks bisy. No, I did not realise there are two thermostats on a Golf oiler!.
The problem is still there, but the summer weather has helped.
I have been away from the forum for a while and had not realised that there were so many responses. The temp probe, whilst an obvious clue, seems OK because the oil temperature is low, unless the car is on a long, steep incline.
In desperation I had the 150K service done by a VW dealer workshop with a special request to run diagnostics, focussing on the cooling system. The mechanics took it for a road test (true, I was in the waiting room/lounge and watched it happen) but no error codes appeared.
However, it still runs cool.