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AznDrgn · Guest

Workin on my '78 NA since I'm back from school and I'm just trying to square away a problem that I've had on this car. When I start the car up the oil pressure gauge reads about 4 to 5 bar which seems fine. But once the car starts up and runs for about 20 min idling the oil pressure drops to about 1 bar or less and the oil pressure warning light comes on. The light will go away and the pressure will come back up a little if I rev the engine slightly. The engine seems to be getting oil alright and everything but I'm worried about the gauge reading low. Anyone got a solution? So far I've changed the oil, and used engine cleaner to try and clean the engine and changed the oil again(this seemed to help a little goes a little longer before oil pressure drops). Also another thing that comes up when the oil pressure light comes on is the emergency break light on the center console, I dunno if that has anything to do with the problem though.

Thanks

Zuffen · Posted: Fri Dec 14, 2001 2:23 pm Post subject:

My quess is the cam journals are getting on the oversize. You can have the caps machined very slightly to tighten up the fit.

But first check your sender and gauge

The best bet is to add a mechanical oil gauge onto the engine and then test the electrical one if the problem appears to be in the dash.

_________________
Bob Dodd - 924turbo@cox.net
931 1982, 944 1982 euro, 924S 1988SE, 93 968 tip 06 Silver Cayenne S, 06 Black Cayenne S

I have Way too many cars, parts for the 931,944 and 951

larso · Guest

Yeah something has got to be wrong unless the sender is bad...if you can't find a mechanical one try one from an audi or ford, the generic one that was bought at a Napa a few years ago fit right in that I had, just find the same thread. Don't pay 80 dollars for a new sender is my vote.

You could try putting some really really thick grease in the cam journals, and start the car up...if it helps the pressure a lot then it's probably them. Don't run the car for a long long long time with this grease in there!

kaffine krazed · Guest

What kind of oil are you using.

Hook up a mechanical oil pressure guage if it reads low You can try using a thicker oil somthing W40 or W50 preferable nonsynthetic.

I don't know about the 924 since neither of mine run but the 944s oil pressure will read very low on the guage when idleing hot.

AznDrgn · Guest

I'm running some cheap wal-mart brand 10W40 oil right now since the car is not being driven and only runs for testing. Thanks for the help, I'll check into those things and see what happens.

AznDrgn · Guest

how do I check the oil pressure sensor, I was looking at my haynes manual and I didn't see anything obvious on it and I looked in the tech section here and I still didn't see anything.

Thanks.

RobE · Guest

The owner's manual for my '79 calls for a minimum oil weight of 20w50. Try that first before spending too much time trouble shooting anything else.

larso · Guest

It should have OK pressure with 10W30, 15W40, 5W30, should be pegged at about 7 when you start it no matter what oil you use...20W50 is only good if you live where it is 80 degrees and up all year round probably.

Mannghi · Guest

I have the exact same symptoms in my '77.
I bought a good used oil pump to correct the problem. Haven't fitted it up yet though. I'll probably give it an oil change with a heavier weight oil first. I have a sneaking suspiscion that the crank bearings are worn and not keeping good pressure.
I don't follow why the cam journals would be affecting the pressure that much? Thoughts?
let me know if you get any results,good luck.

wdb · Guest

just a thought .if you remove the valve cover,to check cam and plastic elbow,retorque head bolts while your in there.if you cant find or fix the problem soon,try S.T.P. oil treatment,it is as thick as honey when cold.maybe 2-3 bottles,or 90 wieght gear oil,to protect the expensive bottom end while your looking.you brake light suggest you have a bad ground,which could also cause the low reading.

Mannghi · Guest

The tech FAQ was dead on about the cam oiler elbow being broken, it's a no-brainer to check too, five minute job. Plus, you'll know if your cam has been starving for oil.

AznDrgn · Guest

Everything seems to check out ok, only thing that I haven't checked is the ground. But while I was wandering the site found this section in the FAQ which says that at hot idle the oil pressure light coming up is normal. So it seems that there really is no problem.

"At 80 to 100 deg C oil temperature and 5500RPM, the pressure should be not less than 7kp/cm^2. A slight drop in oil pressure is normal under certain operating conditions such as prolonged highway driving in hot weather. At idle speed, with the engine oil hot, it is permissible for the red warning light to light up - this does not indicate any loss of engine reliability."

Mike77 · Guest

I have the same problem, including the part about it being ok for a while after the oil change and then getting worse. I discovered that my oil was being polluted by gas which was making the oil too thin. I just got some new injectors since mine seemed to spray too heavy and drip, so hopefully that will solve things. My car is still in the project stage so I haven't tested it for long hiway drives.