View Full Version : 98 2.8 quattro RANDOMLY OVERHEATING AND LEAKING COOLANT!!! HELP!!!

10-04-2011, 04:14 PM
I have a 98 2.8 quattro a4. Twice now after the car has been driven for a while the car will start smoking from under the hood and then i will notice a **** load of coolant running out from under the car. The first time I was just parked with the car running and AC on for a while and notice the smoke and got out and noticed that the coolant was leaking out and running out from under the car. The second time after being in bumper to bumper rush hour traffic for about and hour I noticed the same smoking from under the hood but was not able to get out and look until the smoking stopped. The second time when I finally pulled over and parked my coolant tank was almost empty about the exact same amount as the first time but the car was off and the hose running from the coolant tank to the top of the radiator was like vibrating like coolant was bouncing around in it!

I believe the smoking is the coolant leaking onto the hot engine to tell you the truth because after i got out of the car the second time the car was covered in like burnt sticky coolant fumes around the grill and the driver front wheel well. I know my ECT sensor is bad because my coolant temp gauge in the car always sits on C and both times when this overheating/leak occurs the gauge might jump to H a few times.

Also recently I noticed it during the last overheating that my oil temp is running at about 250 degrees. I dont think this is normal either.

Please tell me what could be the possible cause of this! Is it possible that my coolant flange is bad? please help me out! can someone send me in the direction of a picture of the flange for my 2.8 and also a picture of the ECT sensor for my 2.8? Thanks SO SO MUCH in advance!

10-04-2011, 05:22 PM
- There is no crappy plastic flange on your V6. The V6 engines use a metal pipe across the rear of the engine. Looks like this:
They do have o-rings which can fail, but it is not common. It is somewhat common for the CTS o-ring to fail and cause a leak, though.

- In this situation, I would suggest you get the cooling system pressure checked to find the leak. It is currently unclear whether there is leak causing an overheat, or the other way around. A pressure test is a good first step, though.

- I would also advise replacing the CTS. It's cheap and no reason not to do it. I would want to do the pressure test first, and replace the CTS afterwards. It would be in the best diagnostic interest to pressure test the system to find the problem before anything is tampered with. That way you are more certain that you found and fixed the problem.

- From your description it sounds like the car may be overheating when running only while sitting still. If that is the case it could be that the fans are not operating properly. So that is something else to check for.

- Of note is the fact that your V6 engine uses a plastic impeller water pump from the factory. The impeller can break apart into pieces causing zero flow. It can also slip on the shaft causing a more intermittent issue. It is highly recommended to have the water pump replaced with an aftermarket metal impeller unit at time of timing belt service. It is also wise to have the t-stat replaced at that time as it resides behind the timing belt.

- Your high oil temp (along with the steam) is a pretty good indicator that the engine is actually overheating. On these Audi's there is always the possibility that the CTS is lying and reading a false overheat situation. That is probably not your situation however. I would be careful not to let the engine overheat again, as continued overheat conditions can cause more expensive issues as I'm sure you know. Good Luck.

10-04-2011, 05:52 PM
its most likely coolant temp sensor in the back. same thing happened to me a year go. super easy to fix!

10-04-2011, 06:02 PM
The overheat is causing the leak is what I was trying to explain. So you suggest I have the system pressure tested first to see where the leak is then go from there?

10-04-2011, 06:08 PM
also what does the ect sensor look like that would go in my car? this http://cgi.ebay.com/ebaymotors/Original-Engine-Mgmt-8365-Coolant-Temperature-Sensor-/160656712513?pt=Motors_Car_Truck_Parts_Accessories&fits=Year%3A1998%7CMake%3AAudi%7CModel%3AA4&hash=item2567e2e341 or http://cgi.ebay.com/ebaymotors/COOLANT-TEMPERATURE-SENSOR-SENDER-VW-AUDI-/160573215218?pt=Motors_Car_Truck_Parts_Accessories&fits=Year%3A1998%7CMake%3AAudi%7CModel%3AA4&hash=item2562e8d1f2 or http://cgi.ebay.com/ebaymotors/FOUR-SEASONS-36444-Coolant-Temperature-Sensor-/170630595060?pt=Motors_Car_Truck_Parts_Accessories&fits=Year%3A1998%7CMake%3AAudi%7CModel%3AA4&hash=item27ba6041f4 or http://cgi.ebay.com/ebaymotors/Original-Engine-Mgmt-8282-Coolant-Temperature-Sensor-/150667202520?pt=Motors_Car_Truck_Parts_Accessories&fits=Year%3A1998%7CMake%3AAudi%7CModel%3AA4&hash=item2314770fd8 . what is the difference between all these different ones?

bastosmafka: you had the same symptoms? and the ect sensor replacement fixed this?

10-04-2011, 06:16 PM
Do yourself a favor and support one of the many vendors here on the forums. Here is a good place to start:


There are 2 versions, Blue with the square connector, and the Green with the D-shaped connector. The green replaces the older black sensor of the same shape. Blue and Green are not cross-compatible, obviously as the connectors are different. Seeing as the split is in the 99 model year, yours would use the Blue square type sensor. Be sure to also replace the o-ring. It is possible that your entire leak is from the failure of the CTS o-ring, but there are other possibilities.

The best way to battle unknown coolant leaks (or even just as a periodic check before a long trip) is to pressure test the cooling system. There is a kit for this that should be available from Autozone under their loan-a-tool program (free with refundable deposit). You screw on the special cap and use the hand pump to crank it up to 15 psi or so (max). Then use a flashlight and find your leaks. The system should hold pressure pretty much indefinitely. So you are not only using the pressure to find possible leaks, but you want to see it hold the pressure without falling as well.

10-04-2011, 06:32 PM
thanks for that info. I will deff support ecs and buy that part from them. do i need the retaining clip?

10-04-2011, 06:38 PM
It is a plastic part so it is nice to replace it as the plastic can get brittle. It can break upon attempting reinstall leaving your car broken because of a 2 cent piece of plastic (that costs 50 cents), which sucks.