Overheating!

[DBA4_1.8t]

I was on my way to school this morning, just cruising along and all of a sudden the coolant light starts flashing on my display. I had only driven about two miles at this point and I pull over, pop the bonnet and check my fluid level. It's right where it is supposed to be so I restart it and the temp gauge shoots right back up to the red and I pull over again. I repeated this process until I was able to get home (one and half hours later for 3-4 miles). So here are the rest of the symptoms: No codes, my EPC light for some reason is now staying on after the car starts, cold air coming from the heater, and all hoses connected, and fluid levels fine. I just changed the valve cover gasket this weekend and had not replaced 2 of the hose clips on the crankcase ventilator, but put them on this morning during all of this. I've searced and found that many people have had this either be a thermostat issue or water pump issue, so my questions are: 1. What do you think my symptoms point to? 2. To anyone who has either fixed or replace, how much did it cost? Thanks in advance for your help!

ps. I am currently at 46k and my radiator was replaced sometime before I bought it (around 30-36k).

[diagnosticator]

OK, sounds like the impeller in the coolant pump has split and is loose on the drive shaft, or has fallen off the shaft all the way. Or, the system is air locked. But because the symptoms of overheating developed suddenly, and was not evident before, it's not likely air locked, but is consistent with the impeller problem. This is a common failure mode with the OEM pump. OEM equivalent aftermarket pumps have a metal impeller.

[Affinitive]

The dead give away to a free spining impellar is when the engine gets hot yet no heat from the climate control since the coolant is not circulating. The good part is that this is a blessing in disguise given the track record of 1.8 timing belts and you're now essentially forced to do the whole timing belt job. I commonly see timing belts starting to crack in 50K range on 1.8T's
The bad news is that the thermostats used on the AMB 1.8T's (B6 1.8T's) are a sad sad sad joke. Also many people will argue that any thermostat needs to be thrown away once overheated. I kinda agree considering how many times I have seen issues with stats imidiately or shortly after overheating issue. The properties of the thermostatic spring which makes the thermostat work will be forever changed after overheated. Again, considering the track record of AMB stats and Audi/VW thermostats in general (all the cooling system performance faults and so forth), you really should bite the bullet and just do the timing belt/water pump job and thermostat together to save money and hassle later down the road.
Some more nuggets of info - AMB and late AWM 1.8T's use a unique timing belt tensioning set up which unfortunately is somewhat misunderstood. The tensioner pulley is actually adjustable and the belt is different so that the timing doesn't have to be set 1/2 tooth off. Setting the pretension is actually quite critical to insure that the timing belt will not start to crack prematurely again (I know, "crack prematurely" is kind of a joke when talking about 1.8T's, but I'm talking about more so than usual, as in like 25 - 30K). I've seen a fair share where people just set the pretension similar to how the 3.0 would be set, but it's not actually correct and leaves the tensioner holding the belt too tight (it's already too tight to begin with but that's another issue all together).
And last - the idler pulley for the serpentine belt is also another weak point of this engine. Cheap part but one hell of a hassle to change out once the front core support and bumper are in place due to the type of bolt used to mount it. So considering the track record of them things, just change it along with all this other stuff to again save the money and hassle later down the road, especially considering how cheap it is. I can guarantee you that the bearing will already be starting to make noise. It's actually a pretty heavy duty bearing when compared to that used on other cars and other makes of cars for their serpentine belt idler and tensioner pulleys. The reason they're a weak point is because of how the belt is routed and amount of load exerted on it due to the belt routing.

WOW, I'm one long winded son of a bean.

And of course, since I'm a business owner and we're in tha same neck of the woods. I work almost exclusively on Audi's and my prices are surprisingly good since I run a small operation.
Feel free to call if you have questions or anything you may need help with.
Colin
Affinitive Automotive
206-280-3673