928mac

Yesterday I noticed when I shut the car off the cooling fans were running. Normal as the engine was warm.
I went into the house and came out a few minutes later and the fans were still running.

Long story short fans will run with the engine cold and key off.

Fans quit when I lift the hood.

I searched but did not find anything out of the ordinary.
I have yet to test the coolant sensor on the rad.

Thanks in advance for any Ideas

Brad

Imo000

Temp sensor on top of the intake manifold failed, pull one of the pins and the fans should stop. OR the engine was really heat soaked and the sensor is fine.

dprantl

But make sure you pin the hood switch first, otherwise the fans will stop when you open the hood.

Dan
'91 928GT S/C 475hp/460lb.ft

928mac

Thanks guys, those are the kind of test I was hoping for.

You know I used degreaser on the engine the other day, I bet it is the sensor.

ILL post back when I pull the car in tonight.

Dictys

There is an transmission oil temp switch which also connects to the same pin on the fan controller (pin 3) if your car is an auto.

928mac

Yes its an 89 euro auto, where is the controller located?

Imo000

If you washed the engine, it's the temp switch for sure. Buy a new one and never was the engine again.

Saw the same thing happen last summer on another '89 S4 from Japan.

Mrmerlin

get a new sensor for the top of the intake,
dont wash the engine

Dictys

The transmission oil temp switch is at the front of the transmission / torque converter, you can see it in PET. I have not located it visually however.

928mac

Ok I find it strang (as a mechanic) that a temp sensor will brake when washed, is there any fac data that I can read on this?

If this is the case I will replace it with a GM sensor of the same size and style.
I assume that it is a simple open/closed sensor or dose it have another purpose then the cooling fans?

Since I am new to the 928 family,
why are there the 2 temp sensors on the front of the engine and 1 on the intake?
plus 1 on the rad.

Speedtoys

Rad sensor is for fans when water is too hot
Rear intake sensor is for when air is too hot
Front sensors are cold start and uhh..temp gauge.

They get water in em I think..I got a new one..problem went away. (the rear intake one)

Maleficio

I've washed down my engine countless times without a single issue. But mine is the 16V.

Sucks that you can't wash down the later engines. I have having a dirty engine.

Mrmerlin

use compressed air to blow the engine off .
the rear sensor will collect water by design,
its not sealed very well ,
and once the water gets into the sensor then it will begin to corrode,
as voltage is passing through it.

Use the correct parts,
dont use GM parts in your 928 ,
and dont wash the engine ,
pretty simple Brad!

Alan

Don't use any GM part for this - as far as I know GM doesn't have intake temp sensors for this purpose on any engine - so there won't be any kind of equivalent..

The reason for so many sensors is that this is a Porsche - and their engineers consider all kinds of things that other manufacturers don't bother with... so everything is more complex than a GM or Ford..

Alan

928mac

Thanks guys, its disconnected for now.
ILL order one from Roger.

Roger if you see this before I e-mail you, drop it in the mail and send me a paypal request, unless its thousands of dollars