MBMB

Valve on water line from reservoir in 1989 928GT.
What is its purpose? Its part number?

Thanks,
MB

Speedtoys

Cooling system pressure sensor.

jcorenman

This ^^^

It's a pressure switch on the line from the reservoir to the radiator. It is part of the low-coolant warning light ('84-up).
Here is the description from the '84 model-year service info, still a mystery after reading this many times:

MBMB

Thanks!

PorKen

That sensor puts the idiot in idiot-light and it will eventually start leaking, if not fail completely.

Many people replace it with a 5/16" (8mm) connector and a new section of hose.

Adk46

If I've parsed the Porsche document correctly - big "if" - the pressure sensor is there just to put out the warning light if the cap is opened to add coolant, which the car would otherwise keep on even after the coolant level becomes OK after warm-up.

It's difficult to imagine how this idea survived an engineering review meeting, unless it involved a manager's nephew, or if forced upon them by a manager. Perhaps it was offered up to kill an idea for an elaborate automatic coolant level control scheme, for which we should be grateful.

MBMB

PorKen,

Leave the electrical connection open?

MB

PorKen

Yes. Leave it unplugged. (Wrap in black cloth tape for a factory look. )

(Same with a faulty level gauge - though I recommend replacing those.)

ammonman

Can you post a nice clear picture of the plug housing showing the numbers etc.? Mine has gone missing (the switch is there) and I can't seem to identify the part.

Thanks

Mike

skpyle

Mike, see if these help:





























From PET, it is part number 928 641 513 00, Pressure Switch

GregBBRD

No. That will trigger a warnimg, in cettain situations. The best thing is to leave it attached to the sensor. I generally split the sensor in the middle and just leave the electrical half hooked up.

SeanR

I just unplug them, what issues are you encountering?

GregBBRD

It's been so long ago, I can't remember exactly what happened.

However, under some scenario, the idiot light went off, and I had to re-install the electrical portion of the switch.

I've just always done that, since then.

Thinking about it now, the switch measures resistance.....it's not an "open/closed" switch.....so leaving it still makes sense to me.

This is almost not worth the bandwidth.....do what works, for you.

SeanR

Just making sure I wasn't missing anything, thanks. I usually just pull the damn thing out and put in a line connector leaving it unplugged. First time I encountered it was in my car back in 2006 or so. Driving in the Texas heat, car started to over heat and lost coolant. Amazing what a little bit of pressure loss will do on these.

ammonman

Seth, I need pictures of the plug housing on the main harness. My pressure switch is in perfect condition. Or just carefully separate the plug housing from the harness on your car and send it to me for "recycling" onto my car.

Thanks

Mike