kevinlieb

The coolant light on my '88 S4 keeps coming on. Not every time I drive it, just once in a while. Sometimes right at start, sometimes after I drive a few miles and sometimes after even 25-30 miles. I looked in the coolant reservoir of course to make sure the coolant level is right and indeed its fine.

So my question is: where is the sensor for this? Is it a float type sensor or pressure or something else? Is there another way to confirm coolant flow is ok (besides that the temperature is stable, which it appears to be)? I want to make sure I don't break this car.

Thanks in advance!

Ducman82

got coolant in the coolant tank? thats where the sensor is. passenger side rear corner..

Randy V

What is the exact wording for the warning light that is illuminating?

kevinlieb

Yes I did check the levels and it appears ok.

The light says "Coolant" and the ! symbol goes on.

Chuck Schreiber

That is probably a faulty coolant level sensor.

My resv was full, sensor was bad and I kept getting a coolant level warning on the message center. The pre-89's have just a warning light that says COOLANT IIRC.

Replace the tank along with the sensor as It is probably not to far from having a crack in it, you'll have to remove it to get the sensor out anyway. I'm assuming it probably looks like $@@T as well. Mine did.

I did this job a few weeks ago. Hardest part of it was getting the dang drain hose (bottom of resv) to the Y pipe on the fender well. Finally used a bunch of polmolive dish soap on inside of the hose and pushed it on. True what they say about using plenty of lubrication!!

NC928S4

Sounds like the coolant sensor & cap assembly(928 641 503 01). 928sRUs has this part that has come in and out of NLA so get it while it is available. Per others on the forum you might want to get a new reservoir tank. The cap is a Royal PITA to change out so WYAIT do the tank.

Not seeing the false warning light while cruising around is way relaxing...

Randy V

The coolant warning light is also activated by the coolant pressure sensor, located by the right strut tower.

kevinlieb

Thanks all.

Any way I can tell if it is the level sensor in the tank, pressure sensor at the right strut tower or ???

Barry Chan

if you follow the tube from the bottle to near the right strut tower area, you will see a black plastic unit with wires and connected to a hose to the radiator and search "coolant pressure sensor" you will find answers to your question/problem.

LeRox

Had this issue last week when first driving the car after the intake re-fresh.

Driving along and the coolant light/ACTUNG warning lights come on. Hit ACTUNG reset and coolant light/ACTUNG comes on again and again, etc. as we drive along. The gage reads OK and we check coolant tank, it’s OK. We keep driving and the way its acting (coolant light/ACTUNG Light), I get the sense it’s a short.

When we return to the shop, I ask where the temp sensors are on the engine. We look at the one on the WATER BRIDGE first and notice one of the connection pins is loose. Slightly re-crimp the pin, reattach to sensor and here-weeego.... its fixed.

soontobered84

Kevin,
You can simply disconnect the plug from the coolant pressure sensor. If the warning doens't come back, that is your culprit.

kevinlieb

Thanks for the advice all!

I'm going to start calling it the ACTUNG light now. I love that!

I saw where both the pressure sensor and level sensor are now. I can more easily diagnose now that i know what i am looking for. The pressure sensor was definitely gunky, like it had been leaking a bit. Looks like the level sensor won't come out without taking the tank out, as everyone warned here. I think i can raise / lower the float by hand and test it out ok.

Barry Chan

i bypassed mine because i still get warning from the level sensor if low coolant, all it does is to keep the coolant warning light on until you open the cap and refill, it's $100.00 to replace.

95carrera

Where exactly is this?! Can't find photos on Google.

Yes I know this is an old thread. I want to disconnect sensor cause my light keeps coming on, fluid level is fine.

worf928

Black, circular plastic thing about the size of a silver dollar about 3" from the reservoir towards the front of the engine bay. One of the little 1/2" hoses from the top of the reservoir goes to it on one side and out the other is another 1/2" hose.