careful1

I was under the car, ( 1988 S4)adding trans. fluid , the car started spewing coolant . I had the car running for quite a while to make sure the trans oil temp was hot enough for proper levels in the container. The place where it was leaking from was the hose that comes from the top of the radiator ( driver's side) and goes into the overflow plastic container. To be more precise , it blew the top off an electric type solenoid that is located just before the white plastic tank. The fans had been working fine. I have had to add coolant before so I'm wondering if this is a weak spot or is there something more sinister lurking? The coolant did drip sometimes from that general area, but could never pinpoint exactly where. Any thoughts? Also, I'm going to need a new part. Does anyone know what it is and maybe part number. Thanks as always, Doug

PorKen

That's the coolant pressure sensor (928 641 513 00). Very common for them to fall apart, or make for a mystery coolant leak.

I think this is the most common solution (5/16" hose adapter):

careful1

Thanks Ken, what does electric solenoid do?Do I need to replace it ? By the way, I received the lift bars this afternoon and man are they beefy. They are working great. Thanks ,Doug

SeanR

Just pull it out and by pass it.

Barry Chan

that's what i did a couple of months ago, replacement is like $100.00, you still get a coolant warning if coolant is low, that just keep light on until you open the cap and add coolant, light goes out.

jthwan22

Would it set off warning lights if it is bypass and unplug?

soontobered84

No

careful1

Thanks for the replies to my question. I decided to get the part and fix it right. In the mean time , I used the barbed connector to make sure it was only the sensor blowout and not another reason . I was concerned because the temp gauge spiked. It appears that the blow out with pressure loss caused it along with fluid loss . Also , thanks to Roger @ 928sRus for all his help and advice, Doug.

WallyP

Doug,

The function of the pressure sensor is to ensure that a low coolant level warning doesn't go out when the coolant expands.

If the coolant gets low and a warning is set; then you shut the hot engine off for a few minutes and then restart, the coolant will have expanded enough to be over the warning level. Without the pressure sensor, you would get no low coolant level warning on that restart, even though no coolant has been added. With the sensor installed and functional, as long as pressure is on the sensor, it will hold the low coolant warning.

careful1

Thanks Wally.

namasgt

What exactly fails on the old sensor? Has anyone attempted to repair the old one and reusing it?