All Things Mk5 > How to Guides / Troubleshooting
Operating Temperature Not Reaching 90
lukemk5gti:
I've seen over the past while that this is quite a common issue.
The coolant temperature should reach 90degrees after a few miles of driving from cold but when it fails it tends to only reach 90deg when idling in traffic or doing city driving.
I currently have this problem which judging by my symptoms I imagine is my main thermostat.
Note - I have a manual so don't have the DSG sensor
I had alignment booked in with VW on Friday so they said they'd take a look at the main thermostat for free and reported that it was working fine. This happened to be after congested city driving so when I arrived at VW my gauge was at 90deg.
I tried to explain this to them but I really got little to no help on the matter.
I don't want to shell out €400 to replace the main thermostat nor do I want to spend 6 hours under the engine trying to replace it myself until I can guarantee what the problem is.
Does anyone know how I can determine this? Or if it could be anything else?
john87:
I'd like to know how they managed to prove that the thermostat was working fine as it's purely a mechanical device; it's not controlled electrically like other 'valves' on the car..
My money would still be on the stat being stuck in the fully open position :happy2:
lukemk5gti:
--- Quote from: john87 on October 20, 2014, 09:58:18 am ---I'd like to know how they managed to prove that the thermostat was working fine as it's purely a mechanical device; it's not controlled electrically like other 'valves' on the car..
My money would still be on the stat being stuck in the fully open position :happy2:
--- End quote ---
Good question but I actually was looking at this. With VCDS you can give the thermostat a code and tell it to open/close effectively. If it responds it's working, if it doesn't it's not.
It won't give an error if you scan as it doesn't provide feedback but if you tell it to do something and it fails you know it's broken.
marko:
Faulty temp sensor??
Common on vw's
lukemk5gti:
--- Quote from: marko on October 20, 2014, 03:51:44 pm ---Faulty temp sensor??
Common on vw's
--- End quote ---
That was original thought but after some digging on the forum it would appear due to my symptoms I'm most likely looking at my main thermostat.
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