A4 B6 1.8t AMB overheating issue

[qccoles]

Overheated on the highway, going about 70mph. After getting it towed back, I noticed a crack in the neck of my Dorman coolant reservoir, and coolant coming out of the drain hole. Replaced the reservoir, overheat problem still exist.

I've bled from the heater core hose, the bleed valve on the upper radiator hose, and even leaving the cap off.

Very little to no heat.

At idle, it won't overheat. But once I start driving, overheating starts.

I've noticed the radiator fans aren't coming on until the car overheats, and if I idle down, they'll cool the motor down enough to put the coolant temp back at the normal level. But will continue to overheat if I keep driving.

After shutting the car off, I can feel coolant traveling through the top hose from the reservoir.

I've only felt both hoses after i've shut the car off, after an overheating condition(will try it with the car on tomorrow) and they are both the same, cool to the touch.

Any ideas what this may be? Thanks

[jonan]

have you tried bleeding the system through the hole on the upper heater core hose?

[V70R]

Do your fans work? Fans turn on when A/C is on? Also, when the car is turned off do you hear any gurgling or air pockets that may be trapped that is trying to escape? Check for codes, particularly if you have access to Vag-Com and complete a scan.

[BISHILVR]

Im going with your waterpump being bad or your stupid electric thermostat not working properly, other than that it could be a cracked head or bad head gasket. Audi decided to run the B6 1.8 at 230*F for emmisions reasons, this engine was designed to run at 190*F and did so for years with no major problems, as a last ditch effort to keep the 1.8 around longer Audi tried to clean up the emmisions output by running the engine in a overheated state which explains the large increase in blown head gaskets and cracked heads on the B6 A4 over the old B5 models, your cracked coolant tank might be a result of too much pressure in the cooling system from the overheat rather than the actual problem.

[old guy]

[qccoles]

have you tried bleeding the system through the hole on the upper heater core hose?

I've tried doing this numerous times. My procedure was to pull the hose back far enough for coolant to come out of the hole. Start the car, turn the heat and fan all the way up, allow the car enough time to heat up and theres a steady stream of coolant. Then push the hose back up, and turn the car off. The coolant doesnt really spew out from the hole, but the hose is warm and the coolant just dribbles out slowly. Is this the correct procedure?

Do your fans work? Fans turn on when A/C is on? Also, when the car is turned off do you hear any gurgling or air pockets that may be trapped that is trying to escape? Check for codes, particularly if you have access to Vag-Com and complete a scan.

I cannot get my fans to turn on with the A/C or heat. They only turn on when it's too late, after the temp gauge needle begins to leave the 12 o' clock position and the car is overheating. I don't believe I've heard any gurgling. I do have the cheap ebay KKL cable and I can attempt to use vcds lite, but not sure if the free version will be very useful.

Im going with your waterpump being bad or your stupid electric thermostat not working properly, other than that it could be a cracked head or bad head gasket. Audi decided to run the B6 1.8 at 230*F for emmisions reasons, this engine was designed to run at 190*F and did so for years with no major problems, as a last ditch effort to keep the 1.8 around longer Audi tried to clean up the emmisions output by running the engine in a overheated state which explains the large increase in blown head gaskets and cracked heads on the B6 A4 over the old B5 models, your cracked coolant tank might be a result of too much pressure in the cooling system from the overheat rather than the actual problem.

Is there any way to be certain it's the thermostat or the water pump? Any way to test either one? I plan on pulling the thermostat today just to make some progress, even though I won't have another one to put in. The oil and coolant look normal, can't see any mixing of the two. Exhaust smells and looks okay.

[jonan]

you've already taken all the steps to eliminate every other potential cause for the lack of heat, i'm with oldguy, your water pump is probably toast...

[qccoles]

Isn't his picture of a water pump?

[jonan]

Isn't his picture of a water pump?

yea, sorry, i meant water pump...and i'm off to get some coffee to cure my hangover....

[old guy]

Testing t-stat: Clicky click

How it should work: Clicky click

[V70R]

If you have your thermostat off and have not re-installed it, grab a small inspection mirror and light and try to see the condition of the plastic impeller. The overheating at highway speeds does sound like a water pump failure...

[CyberPMG]

Check the end tanks on both sides of the radiator to feel if both sides are warm. If it's hot on one side and cold on the other side, that can indicate the radiator is blocked and would either need flushed to clear out the blockage or replaced. Mine was cold on one side and needed replacing. Sounds like the water pump may be the culprit though.

[jonan]

Check the end tanks on both sides of the radiator to feel if both sides are warm. If it's hot on one side and cold on the other side, that can indicate the radiator is blocked and would either need flushed to clear out the blockage or replaced. Mine was cold on one side and needed replacing. Sounds like the water pump may be the culprit though.

earlier this year i was having a ton of cooling issues...i just said to hell with it and replaced my radiator, upper and lower radiator hoses, coolant expansion tank, thermostat hoses and oil cooler lines when i did my 2nd timing belt job...solved all of my problems

the only original parts in my cooling system are the turbo coolant line, hard pipes and (ironically) my heater core!!! it was 30 degrees today and my car was pushing out heat nice and toasty before the needle even made it halfway to normal operating temps...

[qccoles]

Update...ordered a metal water pump....finally got the old one out....and to my surprise, it was already metal...and didnt seem to be in bad condition at all. Left the car sitting for the night and will put it bacik together tomorrow.

Back to square 1. The fact still remains that the fans wont spin until the car is overheating. Could this be a symptom of a failed thermostat? This is my first car with an electronic thermostat(and my last, hopefully)...so I am not sure how they work.

I know the fans may need a new fcm....but i'm hoping that not the case. The car overheated in the highway so I doubt lack of airflow was the issue.

[Let it snow]

Check the end tanks on both sides of the radiator to feel if both sides are warm. If it's hot on one side and cold on the other side, that can indicate the radiator is blocked and would either need flushed to clear out the blockage or replaced. Mine was cold on one side and needed replacing. Sounds like the water pump may be the culprit though.

What CyberPMG said about the radiator sounds right. Since your pump is good there may be something restricting coolant flow. This could cause poor heat and overheating. Radiator being plugged or a thermostat that is not fully opening could restrict the flow.

[Menyahs]

I had issues a few years ago with my car not getting fully up to temp and would also occasionally creep up to between 1/2 and 3/4 on the gauge. It would only get too warm once in a great while so I just watched it and didn't worry too much.

Many others will reiterate this but DON'T IGNORE IT. I would say don't even drive the car until you figure it out. I started a road trip with mine like this, ran great for the first 5 hours, then when I stopped to refuel it ran hot and wouldn't come down, even in 12 degree temps. Ended up being a faulty thermostat and stranded me in the middle of nowhere. Warped my head so $2200 and 3 weeks later I finally got my car back and was able to drive back to Florida.

These engines will not tolerate running too hot, and it can easily destroy an your engine. . . ask me how I know I would say spend the money and replace the thermostat.

I just replaced mine again last week with a refresh kit from ECS with the Billet J Plug. It was less than 3 years old and was sticking open, the plastic J plug was also broken in half and leaking coolant.

[ECS Tuning-Audi]

How many miles and is there any documentation of the thermostat being replaced? If not it could very well be the issue. It's not uncommon for B6 1.8T's to experience thermostat failure.

It's also worth flushing your radiator if you have the front end in service position.

Jason