Ketchmi

I am working on a friends 89' S4 and have a cooling problem that I can't seem to solve. The louvers are fixed open, just installed a 75C thermostat and it's still running just above the high white line. It had no pressure until we replaced the cap, still not it. Now with pressure and no obstruction in front of the rad, it still runs 1 needle width above the high white. (same place as before repairs......)

As a secondary point, he had the system flushed last year and filled with a supposed 5 year coolant. It came out brown looking and seemed to have a lot of sediment in it, but not so. Nothing settled out and it feels and smells ok. Anyone ever encountered anything other than pink, orange or green antifreeze?

For the records, it's a 60k mile clean origional, well maintained with no other problems.

Anyone?

Dave <img src="confused.gif" border="0">

WallyP

First and most important question - Is it really running hot, or do you have a typical inaccurate temp gauge?

Max

Wally, I think as the summer heat continues to clime, we will see more of these same questions.

If you were to install an aftermarket gauge, where would you install the new sensor?

Do you know if one of the current temperature sensors can be taped into?

What proceedure would you go with to qualify the factory gauge and sensor?


Thank you for your continued support, Cheers

Max

Mike Schmidt

Speaking of temperature gauges, does anyone know what temperatures the two white lines on the gauge correspond to?

Anyone know what the resistance values for the senders for the various gauges is supposed to be at different readings? As long as I've got my instrument cluster apart, I'd like to be able to make sure the gauge needles are on correctly.

Jim90S4SFCA

Hi,

I have a 1990 S4 and it also runs right at the last white line or just a needle width above the last white line. The last white line doesn't have a number value next to it but it is between the 170 line and the 210 line. If this line is half way between the two other lines, it should indicate 190, I think [(170+210)/2]=190

I believe the normal operating temp for this car is 195 (I'm not sure but that's what I recall from previous posts). So if the car should operate at 195 and if the last white line is 190, this is where the gauge should be during normal operation.

Is this a correct assumption or am I on the edge of an overheating disaster.

Thanks

Jim

Bernie

hey guys,
No real input here except to say that my '85 temp lives about an 1/8" above the first white line during normal highway driving. Goes up a little when driving city streets and will slowly crawl almost to the top white line in rush hour traffic.
As soon as it hits that line, my e-fan kicks in and down it goes.
I have never seen my temp gauge go over the top white line FWIW.

Cheers
Bernie

Max

Dave, Mike, Jim and Wally, I have been struggling with this for as long as I have owned my 89. When I first bought the car it was running on the last white line all the time, unless I start driving it hard. Then it would get at least two nettle width past and one time I reached the warning stage (really twice, but that’s a long story)! After going through the diagnostic procedures lined out in the SM, cleaned all ground and related connections, doing items 1, 4 and 5 listed below (yes, I’m on # 2 spoiler, same long story). I was able to get it to run almost in the middle of the gauge and it never went above the last white line again (well almost never again).

So far I have:

1. Blown out yhe condenser and radiator with compressed air, this helped a bunch.
2. Removed air flaps and control motor, helped a little.
3. Sealed between the top and side of the radiator and Condenser with open cell foam, this helped get the A/C to blow a little cooler and I hope to see a little more radiator temperature improvement after the spoiler install.
4. Thinned the anti-freeze (AF) to about a 35 (coolant) /65 (water) split (I’m only using the AF as a lubricant) and adding a dose of Purple Ice to the mix (Royal Purple water wetter), results unknown as I’m still working on it and it’s still on jack stands.
5. Reinstalling the lower spoiler, results unknown as I am still working on item 4 and a few other things.

Things I still want to do:

1. Install a new remote engine oil and automatic transmission cooler to by-pass the ones in the radiator end tanks.
2. Check transmission pressures and temperature.
3. Install aftermarket water temp, oil temp and oil PSI gauges for diagnostic work (I wander if one could do water PSI as well).
4. Reduce under hood temperatures.

HTH, cheers

Max

WallyP

Some pretty random, off-the-top-of-my-head comments about temperature gauges:

I don't know of any vehicle that has a really accurate temp gauge, and the 928 is no exception. When you add in the potential for extra electrical resistance in each of the connections between the battery and the gauge, it is a wonder that it works at all!

It would be nice to know the specified resistance for the temp senders, but I have never seen this info anywhere. I suppose that someone could try to measure a new sender, but that wouldn't tell us the spec, only what one sender measured. Same thing with the voltage input to the gauge.

There are several ways to measure the temperature of the coolant. These include:
Using an infared heat gun to measure the temp of the hoses and radiator inlet.
Adding a separate temp gauge (How do you know whether it is any more accurate?) to the system. You can get a mechanical gauge, loosen a radiator hose, stick the probe in, and clamp the hose over the small tube. There are also adapters available that let you punch a hole in the hose and install the probe.
Electrical gauges are available, but you would need to find a good location to install the sending unit - I haven't looked for one.

You can usually tell if an engine is really running hot. The smell is different, it feels hot, and it sounds hot. The idle oil pressure will be lower.

And, just as a random fact - the overheat warning light on some GM cars is set to come on at 245 deg F.

The boiling point of a 50/50 coolant mix at 15 psi is 265 deg F.

joel roeder

i didnt notice a mention to the o-ring behind the thermostat. does this modle not have it? i have found the infored temp guns to be very acurate. good luck

Dozman

With my experience, I have found most infared temp guns to be off, as much as 10%. I have a temp meter that I can use probes, and wire leads that you can touch to surfaces to get the readings.

John D.
'85 928 Auto, Black