Overheating issue - please help!!!
 

98.5 2.8Q-Tip

Temp guage reads high after about 25 minutes of driving. I flushed the coolant, bled the air out, and nothing changed. Aux. fan is not coming on properly - pointing to the thermoswitch, but the overheating happens on the highway in addition to the city suggesting that it is not due to the fan. In addition, when I turn on the A/C to force the Aux. fan on in the city, the overheating does not cease. The fan clutch seems weak and will be replaced, but all of this leads me to consider the thermostat. Thing is - it was replaced 1 year ago with TB. Hose going into heater core is hot, but I don't know what that proves (being 85 degrees outside makes it hard to tell if warm air is really coming out when heat is on, but I assume so since warm coolant gets to the core). Question is: is there any other way to verify that the thermostat is shot? It's a lot of work to switch one out, only to be wrong. My assumption is that it is stuck partially open and not triggering the Aux. fan to turn on (however, if I get in there, I will replace the thermoswitch anyway). Cleaning the radiator with a hose does not work either. Any guidance?????

DP

Fan switch..
 

fan is controlled by a fan switch lacated at the corner of the inside of the radiator not the thermostat. And you may want to change out your coolant temp sensor at the same time if it is the old black one that is prone to fail.
J

Sounds a lot like the symptoms of my car, it ended up being the thermostat.

What about the belt that drives your waterpump impeller?
 

That was what was shot on my car. I just went in to find out what was wrong. Bought all the things it might be beforehand, then found out it was the belt, not the thermostat or fan swich as I thought it would be.

Here
 

<ul><li><a href="https://forums.audiworld.com/a4/msgs/2210208.phtml">https://forums.audiworld.com/a4/msgs/2210208.phtml</a</li></ul>

Re: Fan switch..
 

I am going to replace the fan switch (what I referred to the thermoswitch) anyway, but if this was the problem, why would the car still overheat on the highway? There should be enough airflow to render the fans basically useless. Also, turning on the A/C forces this fan on, and the overheating did not stop. I will take your advice though, that switch and the temp sensor will be changed - I am just afraid that they are not the main problem.

DP

Re: What about the belt that drives your waterpump impeller?
 

If the waterpump were not working, I do not believe that I would be getting coolant up to the heater core. It is there, and it is hot. Looks like I'll be tearing the thing apart anyway, so I'll look at that.

DP

I hear ya..
 

but as you know it is much easier to first replace that fan switch and coolant temp sensor. Besides, they need to be done anyway. If that does not fix the problem, you can bet it is the thermostat. Either way..in the end if it is the thermostat it still is best to update the coolant temp sensor and replace that faulty fan switch. I think you are on the right track.
J

you are correct
 

I have had overheating problems recently as well. In my case, my aux fan thermoswitch was faulty (keep in mind no vag codes as well). Since I did not know what was faulty, I decided to have my fan clutch and thermoswitch replaced.

Keep in mind, I would only overheat (coolant needle would go up to 1oclock position or more) in traffic. I drove 75mph for 4hrs straight and my coolant needle would stay pegged at the 12oclock position.

You can read more about my overheating problems below. Although I have an S4, the cooling system is basically the same.

In your case, as you describe it seems that the thermostat is stuck or your waterpump has gone south. You can test that theory by running your car up to operating temps and *cautiously* grab the hose going into the radiator which should be hot or at least warm. Then grab the bottom hose - the outgoing hose from your radiator. The temperature should be the comparable. If the lower hose is cooler then your thermostat or waterpump is/has failed.<ul><li><a href="https://forums.audiworld.com/s4/msgs/2019252.phtml">https://forums.audiworld.com/s4/msgs/2019252.phtml</a></li></ul>

We had the opposite problem on our 2.8 - car never got fully warm
 

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