Morning

Over the past 2 weeks (since it has got colder) I have noticed that my VRS doesn't warm to 90 degrees Celsius anymore. even after 2 hours of driving it still sits between 50 and 70 degrees - any ideas?

Also on three separate occasions now on a cold startup my Secondary Air Pump has not fired up. Is there a temperature sensor on these cars that feeds the temp gauge and also feeds a signal to the SAIP so it knows when to startup on a cold start? Because if so the two might be related?

Any ideas - suggestions would be greatly appreciated

Cheers

Edited 11 November, 201015 yr by vrs200bhp

Possibly the coolant temp sensor or the thermostat.

thermostat stuck open i would have said mine is doing the same

after 2 hours of driving, would not the thermostat not have opened anyway, and thus with it stuck open, all you would experience is a much slower warm up.

I would suggest maybe a dodgy CTS instead of the thermostat itself.

I have the same problem last year and mine was solved by replacing the thermostat.

Take a look at the connector for the CTS. Pull it off and put back on again.

It is the CTS input that the ECU uses to determine whether to switch on the SAI relay, but it is the other half of the CTS that feeds the dash.

Maybe you have two problems and the thermostat is bad too.

I'd advise you to replace the CTS with a genuine VAG part, & go from there. SAI not coming on wouldn't be caused by a stuck thermostat.

The SAI pump not operating during the winter is normal. From cold start, it will only operate if the coolant temperture is between 5 to 33 degrees C.

Mine is doing something along the same lines!! On a open road driving at 30+ mph the temperature is showing 90 but when I stop at the lights/roundabouts etc. the temperature goes down to just above 80 once a clear open road again it goes back up to 90???

Any ideas people??

P.S. sorry for the thread hijack

Mine is doing something along the same lines!! On a open road driving at 30+ mph the temperature is showing 90 but when I stop at the lights/roundabouts etc. the temperature goes down to just above 80 once a clear open road again it goes back up to 90???

Any ideas people??

P.S. sorry for the thread hijack

That sounds like a classic stuck open thermostat (unlike the issue the OP has).

thanks for the response guys. i will try replacing the CTS first and see if that makes a difference. where can it be found in the engine bay? is it a vertical sensor like the passat 1.8t engine?! also am i right in saying its the green sensor i need from the delaer not the older style black sensor?

thanks again

thanks for the response guys. i will try replacing the CTS first and see if that makes a difference. where can it be found in the engine bay? is it a vertical sensor like the passat 1.8t engine?! also am i right in saying its the green sensor i need from the delaer not the older style black sensor?

thanks again

Green is the updated sensor, get a new o-ring too.

For the 110TDI it is here (CTS-110TDI), not sure for the 1.8t, sure a goggle will help :-)

Arh, google worked a treat, try this link.

Yes and yes. Follow the radiator hose on the right hand side of the engine and youll find it upright held in by a C clip.

It's best to leave the the connector plugged in, & have the new CTS with o ring fitted ready to quickly put in when you remove the old CTS. Then unplug the connector & refit to the new fitted one. This will minimise the amount of coolant lost.

It's best to leave the the connector plugged in, & have the new CTS with o ring fitted ready to quickly put in when you remove the old CTS. Then unplug the connector & refit to the new fitted one. This will minimise the amount of coolant lost.

great tip thank you. will roder one direct from dealer

right gents have now replaced the CTS and all is well, gets up to temp nice and quick (much quicker than before) and stays bang on 90 the whole time. thanks for your time.

cost £28.28 from the dealer - takes about 2 minutes to replace the part. a nice easy fix for anyone that has similar problems in future

done my therostat on saturday as my car was not sitting at 90 now sits there nicely

done my therostat on saturday as my car was not sitting at 90 now sits there nicely

Excellent - just in time for winter!

done my therostat on saturday as my car was not sitting at 90 now sits there nicely

Are they easy to change? I have done a few searches on here and cant seem to find what I am looking for.

Is there a guide anywhere showing how to replace it?

not to bad engine cover of altnaiter needs to be moved out the way about a hour

You need to remove both engine covers. Follow the top rad hose & you will see the CTS. Have the new CTS ready with o ring fitted, pull the c clip out & quickly fit the new CTS & replace the c clip. Remove the CTS connector from old CTS & fit to the new one. 10 mins top, job done.

Are they easy to change? I have done a few searches on here and cant seem to find what I am looking for.

Is there a guide anywhere showing how to replace it?

hi mate. nice guide here on the audi tt forum. Fitting Thermostat it looks like a right pig accessing the bolts to get them on and off. he actually suggests using a magnetic pickup to keep the bolt in place whilst screwing it back together. the method pauldazzle is talking about is the Coolant Temperature Sensor which is a much easier job.

I actually thought i had solved my problem but this morning once again it struggled to get to 90 degrees even though I have replaced the coolant temperature sensor, this now points to the thermostat getting stuck open according to these guys so looks like i may have to take this on at some point

anyone got experience replacing the thermostat - any hints and tips would be muchos appreciated

Edited 15 November, 201015 yr by vrs200bhp

Thermostat is a bit of a pain to replace. I found the easiest way was to take the alternator off its mounting, & then it was easy to access the bolt next to it.

As stated it takes about an hour including refilling the coolant & bleeding the air out.

Edited 15 November, 201015 yr by pauldazzle

as said above engine covers of lock the idler pully of i used a allen key undo the idler 3 bolts .Pull belt of the alt undo the alt 4 bolts pull it out the way you can get to the 2 bolts for the thermostat pull old one out rep[lace put it back together torun the car top up with water and colunt

My car has also started doing this today.

Temperature is jumping between 70 and 90 during normal driving.

Have just replaced the water pump after the impeller breaking and then a coil pack on no.2 cylinder went shortly after. Not using any water and the head gasket seems intact although the temp did go up.

Wondering if this could have knackered the thermostat.??