leftcoastproductions

A week ago my lady and I were sitting in the drive thru and all of a sudden steam started billowing out of the hood. We pulled into the parking lot and the coolant res cap had popped up and there was boiling coolant. We let the car cool down and I added some water in and limped home (2 miles). The following day I checked under the car and there was minimal fluid on the ground but I had to top off the empty coolant tank (did so with the Audi coolant). Drove the car about 20 minutes to the mechanic with no problems. I told the mechanic what had happened and he ran a pressure test and found no problems with the coolant system. He did find the valve cover gasket needed replacing, so we did that. Just got the car back yesterday (2.8 quattro) and drove the car for about 20 minutes before experiencing the same overheating problem while stopped at a light. We coasted down a side road, let the car cool, and I filled the res back up and headed back to the mechanic.

After arriving at the shop the mechanic said the gasket was in bad shape and the car was leaking oil previously so it could be something in the engine. So we let the car idle for about 30 minutes. We went through the engine with an infrared thermometer and hooked up the computer. Bad coolant sensor, however I was told that wouldn't make the car overheat. We couldn't simulate the overheating, and I was told it was because the car wasn't under a load. However the coolant temp got up to about 260 on the computer. The coolant sensor was broken before but started to work sporadically. The fan works, there's no white smoke coming out of the tail pipe, and we drove the car home okay (maybe 8 city miles). The mechanic said if the water pump or thermostat was gone it would have overheated and said he's 80% sure there's an issue with the engine and that I should sell it!

The car is a '98 A6 2.8 with 119,000 miles in fair cosmetic shape. Is there any hope? anything we or another mechanic can check for? at this point I'd hate to throw more money at the car. Anything worth checking myself? I'm no grease monkey, but at this point I have more time than money. The mechanic mentioned maybe bypassing the thermostat so the water runs full time to make it a local grocery getter. But we looked up the service hours and it's almost 6 hours!

Any help or insight is appreciated..

RMsALFA

Any oil in the coolant ? Any water in the oil ?? If no, it might not be a head gasket.

Get it hot and check the radiator in and out - are they about the same temp . Maybe you have a plugged radiator...

Your mechanic said "if the waterpump or thermostate was gone it would have overheated". Sounds like it IS overheating...

leftcoastproductions

no oil in the coolant

We didn't drain the oil to see if there's any water in there. Should we or is there an easier way to check?

I think what the mechanic meant to say was the coolant tank would have started boiling in front of us regardless of being under a load or not. He did put the infrared thermometer all over the radiator and didn't detect any change in temp. Is there a way to test the radiator?

To note the heater core went out a few years ago and we had our mechanic bypass it since it was so expensive to fix. We didn't notice any side effects to this and we were assured it wouldn't effect anything.

Also the last few months there was a pressurized sound on a cold start that would release after the car warmed up (maybe 2-3 min). That sound isn't there since getting the car back from the mechanic.

yakimaA4avant

You don't need to drain the oil to check.

Redneck Truck

Are you sure the fan works? Sounds like both times the engine got hot while sitting still, not while moving or under load. Have the water pump, thermostat, and timing belt ever been replaced? If not, you're lucky it only overheated.

Airbag

My First reaction would be to get another mechanic .. telling you you have engine issues before verifying the fans are running, could be the fans fan switch , relay .. I really doubt it is an engine issue ..but maybe if you keep overheating it ..

leftcoastproductions

Yesterday the mechanic put a rod/clamp on the gas pedal for 20 minutes or so and the fan did come on after awhile.

Both times the engine overheated I had already been driving the car for atleast 20-30 minutes and was at a stand still (drive thru and a bridge yesterday).

The timing belt,serpentine,thermostat,and water pump was changed around 80k.

Yes I'm thinking about getting a second opinion, but need to recoup after paying for the blown head gasket. I thought I'd come on here and see what you all could offer as far as experience/insight.

One thing I might do is replace the Coolant sensor, it looks easy enough. Atleast that way I can monitor what is happening while driving.

Keep the advice coming guys! thanks

4Driver4

This does not sound like a big deal. Fix the fan.

leftcoastproductions

the fan comes on though?

2.7Lturbo

did the mechanic replace the valve gasket or the head gasket?