thermostat

[Quattro90]

Hi i've got an audi 90 quattro sport, i recently replaced thermostat which was jammed open with a new one but now the car is only running at 70oC and when coming to a stop especially when cold the cars revs die then it revs itself back up and a few more times before idling, now to me it seems that the thermostat is still not working properly and was just wondering if you can get two different thermostats one that runs at 70 and one that runs at 90 as i think this is whats causing the problem, help please

[Ski]

Didnt think thermostat had anything to do with revs. Dosnt this suggest ur ISV is faulty/Dirty?

[Quattro90]

the only reason think it is to do with thermostat is the last car i had the thermostat was jammed shut and the revs done same thing then was cured once i changed thermostat but i was thinking along the lines of isv as well but thought i'd try thermostat 1st b4 trying isv seen temp was sitting at only 70

[Ski]

ISV is a lot easier to diagnose, I would start with that. Only costs £5 for bottle of IPA and 10 mins to remove ISV and clean it.

I cant comment on the thermostat questions as i lack knolege in that department.

[volcano rs]

it is possible to get a winter and a summer thermostat not sure about audi .

[mcandmar]

If its a 7A i would say air lock, i get that all the time for some reason which makes the temp gauge read about 60-70.

Air always seems to get trapped in the hose from the head to the top of the rad. Slide the hose off the rad just enough to open it at the top and fill the expansion tank until your getting a steady stream of coolant, then push it back onto the rad. That’s always works for me, the radiator bleed screw will bleed the rad but never seems to clear the head out..

3B/ABY's have a large water manifold on the head that the hose connects to, that difference might explain why they don’t seem to have the same problem with bleeding the head.

[stevieyid]

Hi qauttro 90 how hard was it to change yours in the end? has done anything for fuel economy? anybody got the part number for an aby thermostat? cheers

[Mikes2]

Did it do this prior to changing it ?

If not it's either an airlock in the system which can be cleared by bleeding it or something else was disturbed during the change.

There is only 1 thermostat for the 5 cyl cars in Europe and it's rated at 87 degrees. 069 121 113 although this may have been superceded.

[Quattro90]

it started before changing thermostat gradually getting worse so im goin to try both the isv and the air lock thing as well hopefully this will cure it. Can i ask without sounding stupid what is IPA? its probably blindingly obvious but just finished 12 hour shift and not feeling too great

[Quattro90]

hi steveyid the thermostat was a pain in the **** to do, i ended up cutting a small hole in plastic guard at side of radiator so i could get in to bolts with a socket and take it out once out it was relatively easy to replace. but like i say its still only running at 70oC so still probably running bit rich but so far not made much of difference to economy, I'm thinking that basically the age of the car combined with the quattro system and the soaring price of petrol all together may have something to do with it. I was also told by another audi nut to take the radiator out which lets u get into everything but i really couldnt be bothered on the cold winter morning i done so i took the short cut lol

[Azman]

Slightly easier if you have the patience is to undo the rad and push it back slightly, then fold the plastic forward (infront of the rad). It's still a pain in the **** to get to (when you have hands the size of your feet like me) but it was easier.