1998 above ride
Well i've read and read and have found several great write-ups on changing out the timing belt, water pump etc but no one mentions where the heck the thermostat is.

I don't have any other ideas on what could be wrong and causing the overheating issue.
I've changed out the temp sensor (top left near air intake) and put in a new fan clutch to rule out those. flushed the radiator and ran water through the whole system. I have heat (f'n hot heat) a/c and car runs great. get down the road a few miles and the temp gauge goes to about 80% then goes back down a hair with heat blasting or a/c on. stop the car and it shoots to near max and you can hear a vicious boil from the expansion tank and watch it as it boils around. my only conclusion is that the t-stat is stuck partially open
and needs to come out. anyone agree/disagree on this?? what a friggin pain to have to pull off the front end. I'm guessing it's around the water pump somewhere but can someone verify this that has done this task?
Thanks!

 

As you look at the front of the engine its on the L/H bank just below the Timing belt pulley. You need to put the front end in the service position, (only about 80mm forward) remove the serpentine belt, release the tension on the timing belt & slip it forward about halfway but not off the L/H T/B pulley. Obviously, drain the coolant before removing the T/stat housing. Use a genuine Audi or Behr 'stat (I believe genuine Audi are made by Behr) & new 'O' ring & only use G12++ antifreeze from a VAG dealer.
If the problem is your 'stat then its more likely stuck shut or opening at too high a temperature. With a 'stat (& the rest of the cooling system) thats operating correctly the temp. gauge should get to 90deg. fairly quickly (about 3-4miles) & stay there rock solid even when you're stuck in traffic.
Have you backflushed the radiator & the rest of the system? Hope its not your head gasket.

Good luck.

 

Ooops, sorry - forgot you said you'd flushed rad. & system!

 

Did you "burp" the system at both bleeders after refilling? You may have air pockets that don't allow the coolant to move.

When it starts boiling, are ALL of your coolant hoses in the engine bay hot? If not, then maybe the T-stat indeed doesn't open anymore.
If yes, then your T-stat opens and you should look elsewhere. Do your fans kick on at any point in time, or not?

 

thanks DGSdale I found it ok after your post. for the life of me I could not get the housing out with the TB on. I tried wiggling it, disconnecting the TB tensioner etc....
ended up marking the cam sprockets at TDC and pulled of the TB of the left sprocket.
re-assembled and test started for a few sec. idles fine but mis-fires upon acceleration. from what I have read this could be because none of the sensors are hooked up and the coolant system empty thus giving faulty readings
what are your thoughts on this?
oh and test boiled the thermo along with the new one. new opens quick in a boiling pot and the old one corroded and frozen shut no matter how long the boil! at least I know now that was the overheating issue......

 

What sensors aren't hooked up? I would certainly get everything back together as it should be and the cooling system filled up & bled of air to give it the best chance of working properly. If the temp. sensor (at the back of the engine, on the L/H side - viewed from front of car) has no coolant to read the temperature of, it could cause fuelling problems. It tells the ECU the temp. of the engine so it knows how to fuel the engine (along with a load of other inputs) in any given situation. After that, if you still have a misfire, get the codes read first. It could be completly unrelated.

 

Your timing is off. You need proper tools.