what would cause real poor fuel economy??

[DutchRS4]

Coolant temp should be 90 degrees within a few km's of driving and stay there. Good conclusion. Should be your thermostat. Maybe you can find a used one. Good luck!

[rickoshea]

it looks like a jammed open thermosat but why 700 quid!!!!??

It's a 4 - 5 hr job - the cambelt has to be removed, therefore it ends up being a complete cambelt change / gaskets / tensioners / water pump. Pain in the ar5e.

When an Audi main dealer perform a complete cambelt change, they do change everything.....apart from the feckin' £10 thermostat. Idiots

[Contigo]

Mine in the cold doesn't get up to temp unless idling in traffic but it's running fine and not using any more fuel than normal.

I've spoken to experts about this and they say that the ECU will not overfuel as if it's a cold start if the temp gauge moves off the lowest position. I'm not doing mine until my next cam change is due.

[DutchRS4]

Mine in the cold doesn't get up to temp unless idling in traffic but it's running fine and not using any more fuel than normal.

I've spoken to experts about this and they say that the ECU will not overfuel as if it's a cold start if the temp gauge moves off the lowest position. I'm not doing mine until my next cam change is due.

That sounds more like a sensor problem. Defect thermostat would keep the needle down at all times.

[Contigo]

So you are saying that mine could be fixed by a new temp sensor? Ok will get it changed ASAP.

[rickoshea]

In my experience, a faulty thermostat will allow water temp to reach 90C when idling in traffic. But when up to speed again will start to drop. A correctly functioning thermostat will allow the temp to reach 90C ( less then 10 mins driving - regardless of hot summer or freezing conditions ) and stay there regardless of caning it / idling / crawling along / constant speed.

[maxrs4]

NO NO NO NO!!!!!! i just did the cam belt water pump etc like two fooking weeks ago!!! NO NO NO NO!!! FFS!!!

ahhh well i guess i know how it all comes to bits and know its all been free'd off!

[bastos]

In my experience, a faulty thermostat will allow water temp to reach 90C when idling in traffic. But when up to speed again will start to drop. A correctly functioning thermostat will allow the temp to reach 90C ( less then 10 mins driving - regardless of hot summer or freezing conditions ) and stay there regardless of caning it / idling / crawling along / constant speed.

this is 100% correct! mine did this too. and is now fixed.. just did the cambelt change last week..

[Contigo]

In my experience, a faulty thermostat will allow water temp to reach 90C when idling in traffic. But when up to speed again will start to drop. A correctly functioning thermostat will allow the temp to reach 90C ( less then 10 mins driving - regardless of hot summer or freezing conditions ) and stay there regardless of caning it / idling / crawling along / constant speed.

Yes that describes the behaviour of my car but mine runs spot on, it gets off the lumpy cold start and runs fine even at say 75 deg on the dial. I get the same fuel economy as I did when I was running with a correct functioning thermostat.

[drjones1]

In my experience, a faulty thermostat will allow water temp to reach 90C when idling in traffic. But when up to speed again will start to drop. A correctly functioning thermostat will allow the temp to reach 90C ( less then 10 mins driving - regardless of hot summer or freezing conditions ) and stay there regardless of caning it / idling / crawling along / constant speed.

Yes that describes the behaviour of my car but mine runs spot on, it gets off the lumpy cold start and runs fine even at say 75 deg on the dial. I get the same fuel economy as I did when I was running with a correct functioning thermostat.

Mine is also identical to what has been described above. I'm not using the car at the moment and will probably do it over Christmas. I dont really like running it below temperature.

[rickoshea]

Running an iffy thermostat also means that the heater takes longer to start doing it's thing. Oh, and also takes much longer for the oil to get up to full temp too.

[maxrs4]

where is said thermostat then!?

[Virdee Autos]

behind timing belt!

[maxrs4]

well I'm getting fed up with this now!!! the car has now got a new thermostat and its exactly the same!! took me bout 4 hours all in which was good! but its no different! tomorrow i think ill go for a drive with my mates snapon diagnostics machine and log the drive and see whats going on with that! all i can think of now is maf