My mk5 GTI only seems to warm up to around 70 degrees on the guage. if I hammer it it gets nearer to 90 degrees where you'd expect it to be, then drops back down to about 70 degree's on a cruise.... It warms to the 70 degree point quickly so seems to be warming up normally (i.e not thermostat), and is still sat at the 70 degree point after my 25mile commute, so its definitely actually warm in there... Put a new coolant sensor in assuming it would be this, then the rad fan comes on after about 10 seconds of start up, and stays on for 10 mins after I turn engine off, coolant guage showing the engine as cold (it was stone cold, not driven all day). Both fans came on... big and little, i've never heard the fans come on ever (2 months) with the old sensor in. Have I uncovered a seperate problem? I have put the old coolant sensor back in for now, which after a drive has stopped the fans coming on, but still has the same issue it had.. I've ordered another new sensor, so we'll see what that does... 55plate mk5 GTI if it matters :-)
are you buying the sensors from VW> I would only fit genuine temp sensors as the pattern ones can be inaccurate have you checked the thermostat operation manually, it could be that it is working fine when cold but then opening too early, also some vw suffer from an issue with the stat housign where a part inside snaps off preventing the thermostat from closing fully. could you let me know the engine code from the car and I'll see what I can dig up in etka/elsawin? ideally try to get the fault codes from engine and clocks scanned, and see what the measuring blocks show for engine temperature in the ecu and clocks
I had a strange one with the fans pulsing Fitted a new sensor and had the same problem But once the old fault code was cleared The new sensor worked fine Scan the fault codes and clear them see if that makes any difference
I had this with mine not getting warm on the gauge at all but plenty of heat from the blower. I changed the main thermostat and then found out about these bypass thermostats (2 if you have a DSG). 23 from VW only and now my car warms up to 90 within 3 miles from cold @ 60. I also had my ECT sensor changed but there was a code that showed it had failed. My daily commute is 64 round trip and since I've done this the mayonnaise has stopped which I read was normal on these engines. Hope that helps?
Thanks for the help guys. I have a genuine sensor on the way, and I think I'll change these two bypass thermostats for what they cost as I plan to keep the car for a while. Hopefully that will cure it!
