Looking for just some opinions before I start spending money tomorrow.. Temp gauge on the dash reading strait up, but I'm reading live data from the obdll ader saying its getting to 220 before the thermostat opens..
I want to say it's the thermostat, but I replaced both in October. The car got a bad miss on the way home, I'm talkin bout CEL flashing and by the obdll it got to +230. I shut it off within 45 seconds of the miss starting (which is due to fuel injector harness shorting, p0268). A little wiggle injector wire #3 and no more miss. Back up and go again to see the temp gauge float past strait up and reader showing 235. Kill it and give a bit to cool off.. Make it home and let it cool for a few hours. Come back and find the reservoir empty! Only water found is under the reservoir itself.. Fill it up and watching the code reader again, the thermostat opens at 220... I should say it's an 03 1.8t (amb). I would think that's about 10-15 degrees to hot.
I'm not really wanting to go after the thermostat again, but I thought another opinion couldn't hurt. Give it to me!

 

Well, first things first. I would fix the leak you have that's draining your coolant, then worry about the thermostat.

 

I'm thinking/betting it was a one time overflow from the tank... (wishful thinking). I bought the car more less dead 2months ago, as the thermostat had corroded. So a timing belt/water pump and thermostat were first to be replaced. Then came the overflow/expansion tank, and got to replace the rear flange next. I think I've gone around the engine and replaced most of the plastic.
SO replaced the ect this morning and got the thermostat to open now at 213/215 degrees. It is better than 221 but I'd still like to hear from somebody else with a obdll/vag com that can see theirs at operating temp. The guys at RAI were more than willing to work with me on the thermostat, only I don't want to have to park the car for a week if I'm just being paranoid.
Thanks

 

Thermostat is openning at 100 degrees CELCIUS. seems a bit Odd but it is keeping the engine cool enough. Does the needle stick straight up?

 

I gotta put down as a bad thermostat. It acts sparatic. It open at 215 , then next at 221, and now it's gone as far as 235! Before the needle would stay strait up, but as the temp went goes over 225 the needle pushes past the half way mark.
Well at least I've done this before. It's just ashame it's only been less than 60 days.

 

So now I'm really getting frustrated & confused. Replaced the thermostat and ECT, bleed the system but I'm still getting erratic temps. I'll drive around with obd2 showing live data and the temp rises like normal, the thermostat will sometimes open at 212. Sometimes 221. It even got to 240! At that point I cranked the heater all the way up and it promptly started blowing cold... Thermostat opened and went to 200 degrees. After opened/closed 215 again.
I gotta rule out the water pump as I replaced it with 1 with a metal impeller with the timing belt about 1k ago (when the thermostat was done the 1st time). I'm thinking about another coolant and heater core flush tomorrow. Anybody got an ideas here?? I finally got all the misses out of the ignition system and now I'm backtracking to cooling...

 

I should say also that the water in reservoir is so hot it steams to the point it goes past the cap and drops out the bottom of the tank. No leaks anywhere else. The hose out of the heater core is cold no matter how much I bleed it. I'm thinking I got some kinda air lock or trash in the system.

 

It definitely sounds like you have a plugged up heater core. But that can be addressed later.

Have you checked the mixture ratio of the coolant? Are you sure that it's 50/50?

 

Heater back working this morning.. Still did a coolant/heater core flush.
First did the heater core and it was pretty clean (flushed with clear hoses into bucket to inspect). Proceeded to f
Flush the coolant with the whole hot water thing 4 times through. Got a little sediment out the first few flushes. Followed mixing ratio to ensure 50/50 mix.
Still getting ratio temps. BUT as a member of the male species I am learning to track the pattern. All be it seems backwards though.
The temps stay normal at idle. Rises to 212 then the thermostat opens, taking it back to 190. But when taking the rpm up, the temps rise. Thermostat won't open till 220. Take it on the road and we're talkin 230...
It just seems backwards. I thought the signs of a bad water pump were the temps rise at idle, then the pump would catch up at higher rpms? When my case is the other way around. I know this isn't normal cause the water is steaming out of the expansion tank and dripping from the bottom. Even though the needle on the dash stay in the middle the whole time (the needle was moving fast past half way when it 240 the other night for sure!)
I'm stumped to say the least.. If anybody feels like riding around looking at a real time info of the temp I would be all ears to what the normal is.

 

Scratch the water pump being bad. Took the front end off and removed the pump. No play in it, and the metal propeller is good (it's only been in use 1k miles).
Temps stills getting to the 230 degree area before the thermostat opens. Sometimes it returns to 190, sometimes only 200. The paranoia is setting in..
I bought with a corroded thermostat and the previous owner didn't know how far he drove or for how long it might have overheated. But I only paid 2500 for a clean a4 with 119k on the odometer.
I'm thinking of doing a compression check this weekend to find out if maybe a warped head or just a bad head gasket. Anybody know what the compression #'s should be??
But there's no smoke (white) out the tailpipe. I do get a miss outa cylinders 2&3 randomly only at start up. I can take rpms up and it will go away after 5-7 seconds. I can bleed the system on the upper hard line all night, there's all air in there (maybe that's normal in a pressurized system?). Again, the only coolant leak I get is from the coolant getting so hot it turns to steam and gets outa the reservoir.
There's always two sides to this though. If I gotta take the head off, then I'll break out the foredom porting tool out and clean up the runners in the intake ports and exhaust ports. Looks like that k03 turbo that isn't putting out hardly any boost will get get thrown out for a k04! Gotta get a bigger inter cooler then! Cam seals will get replaced. Think about all the good that can come outa this!