mohsinic

I changed the thermostat , waterpump, and the 50 AMP Fan relay that tells the fan to turn on when it starts heating up, while we were changing the thermostat we also ran a water test on the unconnected radiator and water was gushing out from the other end when put on running water. There is also an Auxiliary Fan Switch that I have ordered online. But my problem is that I do not know what is causing the heating.
Condition of Overheating:
The upper raditor hose gets really hot but the lower radiator hose stays cool and I cannot determine what is causing this. We can safely say that the radiator is working normal. We also bypassed the heater core cause the dealership told us that it might be stopping the water from circulating thru the entire system. The axuiliary fran is not turning on so that is why we ordered the aux. fan switch. Can any body tell me what else I need to do to normalize my heating problem.

JAFO

i'd test the old one anyway.

mohsinic

its actually a 96 A4 2.8 and its a new thermostat

AudiMick

When you remove the thermostat on the 12V a lot of coolant will come out of the top of the block. You need to bleed several times through both bleed points.

If that doesn't work back fill through the heater hoses into the block.

mohsinic

yea I actually did end up doing it but its still overheating, any other suggestions? the au.x fan is not working either i was wondering what all helps turn it on like is it just the switch by the radiator or is there something else that could stop it from running??

Living Dissed

I, also, have a '96 12v, and have just finished a cycle of cooling system work. What finally fixed me was a radiator flush (Prestone), however, if the upper radiator hose is warm to the touch, and the lower going back into the pump is cool, your radiator sounds good.

If it's working right, the upper pipe should be barely too hot to hold. Same for the hose leading into the heater core.

My system never got hot enough to turn on the aux fan, unless I turned on the a/c. This was on 100F+ days in CA.

I'm wondering about your heater-core bypass. It's important to burp the system at the little hole where water exits the heater core, as it's the highest point in the system.

Have you also been burping the pipe coming out of the back of the engine? It's a small hex head, and you don't have to take it all the way out; the plug's flat on one side, so all you have to do is loosen it until a little fluid flows out.

Here's what worked for me:

1. follow the directions on the back of the Prestone Super Flush.

2. When you've drained out the Super Flush, do a series of backflushes

a. There are two pipes coming into the water pump, one 2.5 inches, the other 1.25. Adapt a garden hose to attach to the 1.25.
Remove the upper radiator hose.
Back flush the radiator.
b. Reattach the upper radiator hose, then detach the "in" pipe in the heater core.
Back flush the heater core.

3. Drain
4. Fill with your favorite antifreeze mixture. I tried Water Wetter once, but got the same results with a 50/50 mixture.
5. When it's full, open the valve coming from the back of the engine. This is the one on the driver's side (American), by the cam-timing takeoff. When it seeps, close it to perhaps 15 - 20 pounds foot of torque.
6. Burp the top of the system at the heater core. You do this one by loosening the exit hose from the heater core, and moving it out until air can come out the little hole.
There's a trick here - when level, the bleed hole is higher than the highest level of the overflow resevoir. The Bentley manual has you using a 4-cm extender, so you can overfill the tank. It's simpler to remove the three bolts holding on the tank, and stand it on it's end, so it's level is higher than the bleed hole.

Done! No need to run the engine, or at least I didn't need to.

I put a strainer under the backflush, and all I caught was a couple of tablespoons of silica, but it was enough.

I'm back to work tomorrow, so I won't probably be able to follow up. Best!

My94A4Quattro

I am having the same problem. I just got a 96 A4 2.8 Quattro and on my way home after the 3rd day of owning it, it overheated. It was leaking coolant the first few days that I owned it and I was having to add coolant to it.

Now it starts to steam and or smoke around the water pump area. I am guessing that it is the water pump and I am going to have it replaced along with the thermastat. The fans are working but I cant not run the car for longer the 10-15 min with out it starting to smoke and steam.

Any suggestions?