I just replaced my Fan Control Module because the fans were not increasing speed as the engine got hotter. Prior to the FCM I noticed the fan nearest the bumper would occasionally go to a higher speed but only for a few seconds. With the new FCM both fans speed up and stay at the higher speed. On my test drive to Denver it was 95+ degrees and the temp gauge stayed right in the center with the A/C running. Thought all was fine. Then returning up the hill, to 8300 feet as the outside temperature dropped to the low 80's the car temp rose to the first mark above normal on the temp gauge.

I don't understand. In Denver at 95+ degrees outside all was fine. But after hitting cooler (82 degrees) the car temp went up??? Yes, I was climbing from 5280 to maybe 7000' or so, but it was cooler. Why did the car's temp begin to rise as I continued to climb to 8300 feet? When I got home I raised the hood with the engine running and the A/C on and both electric fans are running on what sounded like high. Faster than they ran for a couple of years. Turned off the A/C and the fans continued at the higher speed. Shut the car off and both fans stayed on but at a slower speed.

Is it safe to assume the temp switch on the lower radiator hose is working properly? I have never replace it. My understanding is if it is not functioning correctly then the fans or the FCM does not get the signal to go to a higher speed. Since my fans change speed going to and staying at a higher speed when the engine is hot that means this temp switch is working correctly. Is this right?

The car has 210,000 miles and has always had the correct Audi coolant. I checked between the two radiators (A/C and engine), it is clean, no build up of dirt or leaves or other obstructions. Do you think the problem is an old and clogged radiator? The belt driven fan appears to run fine. Could it be the viscous clutch? How do I test this?

What else? I am at a loss.Leaving soon on a trip to the East coast and do not want to have overheating issues on the road.

Any help will be sincerely appreciated.

 

So did it actually overheat or did the gauge just go up some? The engine is going to work harder as you continually go up in elevation. Could be the radiator is a little restricted based on age. Maybe find a radiator shop than can power flush the system. You will need one that specializes in European cars as they will have the correct coolant in their machine. Otherwise, if it isn't actually overheating, it may not be an issue anyway. You may have to go to the Denver area to find an indy shop that can do the job of flushing the system.

 

 

If the car is 18 years old w/ over 200k on the clock, and has never had the cooling system flushed, I think I would give that a go. Sediment can build up in the radiator and heater core over time, even under the best of circumstances. You didn't get the overheating indicator on the dash display, so it seems to just be running a little hotter than normal. Probably won't really tell you much, but maybe do a scan with VAG Com. It might tell you if something is amiss. It sounds like the viscous clutch is okay based on your comment. Having the a/c on would definitely put additional load on the cooling system.

 

No codes on VAG Com. I am somewhat skeptical about a flush. I do not want to upset a functional heater core. I assume you can just turn off the heater and it will be somewhat isolated. Also, does this really work for an old radiator? Or should I just bell up and buy a new radiator? Hate spending the bucks on this old car but also hate the issue not being resolved. Moving to a much hotter environment and will not have access to tools to repair this during the 2000 mile move.

Not trying to shoot down your suggestions. Just wanting to be clear. I much appreciate any advice.

 

If done with an actual flushing machine I doubt it would upset your heater core. It is done under pressure using a cleaner fluid to assist in breaking down and removing any restriction, then replaces the coolant and removes any air pockets from the system. I am still thinking a flush is the way to go. Maybe call a couple of shops that you know of and ask what they think.

 

good advice. Thanks

 

As you go up in elevation the air density decreases which also decreases its efficiency in removing heat from your radiator.

I remember my old 5KTQ had a rather marginal cooling system - with 2 bikes on the roof in the high desert of Nevada the temp gauge went into the red if I drove over 75 MPH, which would run the fans at level 3...which sounded roughly like a 747 at takeoff.