Hello guys, i think my VRS may have an issue with the thermostat sticking open, have booked it in with my local independent but want to be sure that im asking them to do the right job before dropping it off with them.

 

My daily commute is only about 12 mins door to door, mix of urban and dual carriageway - car usually gets up to 90C on the temp gauge and sits there, all heating functions normal etc. - happy days. Last few weeks I have been travelling a lot further for work and have noted that although the car gets up to 90C it them seems to drop after a short time and the temperature fluctuates from about 70C-80C on the gauge. This was mostly driving on fast roads, however bizarrely when getting back onto the slow urban roads was when the temperature rose back up to 90C, rather than on the faster roads where the engine was under more load and would expect to be hotter.

 

I did a 120 mile run the other night, nearly all 70mph dual carriageway and using the Torque App logged the coolant temperature, at no point in the journey did the coolant temperature get above 75C and seemed to fluctuate from 60-75C throughout. Noticeably when I turned the heater, the air from the vents was noticeably cooler than i would expect, it did produce heat but only when the heating was turned all the way up.

 

By way of due diligence I have checked the coolant level which seems fine, there are no obvious coolant leaks to my eye and both of the radiator fans appear to be working properly. Water pump etc, were done about 6 months ago. I've scanned the car for codes using an OBD2 reader and nothing coming up relating to the cooling system and there are no warning lights on the dashboard (did have a Coolant Temp Sensor once go on my old MkI VRS which caused the temp gauge to read funny but that immediately threw a CEL).

 

It is my understanding that the car should warm to 90C on the temp guage and under normal operation, remain at 90C at all times., My reading of things is that there's an issue with the thermostat, the car is initially heating up as regular but the thermostat is remaining open, meaning that when the car is on faster roads with more air flow and thus air cooling effect, the stat is still remaining open when it would normally then close and coolant is still flowing, hence the low temp. readings - am i right??

 

Just want to check im barkign up the right tree and not booking the car in for a job that isnt going to fix things! Cheers in advance.

You're right.

My MkII vrs had the same symptoms. Replaced the thermostat and it never moves from 90 degrees.

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Cheers chaos, off to the garage with her in the morning it is!