vcompetello

Hey guys, I've been having a little problem with my oil pressure. Usually when I first start the car it idles at about 3-4 bars of pressure. After driving for 20 min. or so sometimes the gague reads barely 1 bar. At higher rpms I can get the pressure close to 2. I really have no idea how the gague works or if any particular part is prone to failure but I just think it's a little odd that I can turn the car off one night with the light at the bottom of the gague about to go on and the next morning have 3.5 bar at 600rpm. Anyone have any idea what this could be??? BTW I cleaned the ground point under the pod so I think that's out. Thanks for any info

Vinnie
1980 928s euro

Alan

Overheated Oil? check you oil pump, filter and oil cooler.

Are you getting enough flow of air over the radiator? air flaps open? Is the car running hot (water temp?)

If you oil level is low it will heat up faster, if its too full it may foam up and be hard to pump to pressure?

Cold it should still peg the gauge @5bar, Hot it should still be above 2 bar.

If you are hitting 1Bar you should be tripping the horrible "Oil Pressure Insufficient" warning - only happened once but that one scares me...
(in your case the oil pressure warning light anyway).

I'd suspect an oil pump problem since you are low all round cold and hot.

Alan

SharkSkin

What he said -- also get under there and check the connections on the oil sender(don't mix them up). Also check the 14-pin connector near the jump post. A bad connection on the gauge wire would also explain a low reading without the low oil pressure light coming on. You implied that the low press. light works -- it does come on when you first turn the key, before starting the engine, right? If so it should also be coming on in the ~1bar vicinity.

Chuck Schreiber

Might be the sending unit.

Check out Tony's site http://members.rennlist.com/v1uhoh/oilp.htm

IcemanG17

It could be the sending unit, but it sounds like its working...typically when they fail they peg 5 bar all the time? Do you get a low pressure warning light?....if you idle at 1 bar and only reach 2 bar while driving....that is seriously bad....without more info...it does sound like the oil is overheating

Assuming you car (water temp)is not overheating....this is what I would do:

Change the oil pressure thermo (great pics on Tony's site above...its about $40 for the kit) & change the oil-filter to a heavier synthetic oil (mobil one 15-50). This should improve things quite a bit...if it doesn't...then you have a serious oil pump-lines-cooler problem!!

I wouldn't drive the car until this problem is fixed!

vcompetello

Sounds like you guys have some ideas but I haven't driven the car for a while so the problem isn't really fresh in my head. As soon as I drive it again I'll make sure to note exactly what the gague does and when it does itand re-post. Thanks for your help.

vcompetello

OK here's the full story with all the details I can muster. Start the car it idles pinned at 5 bar. Drive for a few minutes and when the water temp gague gets to about 1/3 I notice the pressure start to drop. A few more minutes and the pressure is a little above 1 bar at idle. If I rev it the oil gets to 2 bar at 2000 rpm a little over 3 at 3000 rpm. After my little experiment I checked the oil level. It's a little high but more interesting is when I removed the dipstick smoke came out of the dipstick shaft. I really couldn't check any sepcific mechanical parts because I only have nights free. Now I'm really not too good with hot oil properties so I don't know how the pressure would change, but does this sound like a specific problem to anyone?? I really just want a place to start and I figured if I give a little more info than my first post someone could help me narrow down the problem. Any help would be appreciated. Thanks a lot.

Vinnie

Bill Ball

Vinnie:

The starting pressure is right. Once warm, it should be minimum 1.5 bar at idle and should go to 4-5 bar at 2000 RPM and should be 5 bar at 3000 RPM.

Smoke or steam? Oil level high... Hmmmm... Any frothiness/creaminess in that oil (water or coolant contamination). Any gas smell to the oil?

How old is the oil? What kind and viscosity?

Alan

Well - as before the oil is obviously way too hot...

Could be the oil thermostat, could be that there is a blockage in the oil path through the oil cooler. You should not drive the car like this... take it to someone ASAP. If the oil pump can still peg at 5 bar cold the pump is probably still OK anf the sender sounds good.

If you are really seeing smoke (or is it oil mist?) - you may even have worse issues - get a good Porsche mechanic to check it out.

Alan

If your gauges are correct you are driving with low oil pressure you may wreck the engine... don't wait!

vcompetello

Well now that you mention it...I did smell the oil and it did smell like there was some gas in it...I'm assuming that would wreak havoc on the viscosity but how would it change the pressure?? and what's worse....how did it get in there?? As for your questions the oil is a few months old but has less than 50 miles on it and it's 20W-50...not synthetic. Definitely no coolant in the oil...that stands out wat too much for even me to miss.

Bill Ball

Viscosity and pressure are related, but the good cold temp pressure argues against this problem. You could try to get a small sample of the oil (say, loosen the filter a few turns and allow some to run down into a jelly jar lid) and see if it supports a flame - hold a match over it. Contaminated motor oil will flame easily. Clean oil will not.

I'm just speculating from the high oil level. Gas gets into oil from blocked crankase ventilation (kinked breather?) and cold weather condensation of blowby, repeated cold starts, leaky injectors (any problem with starting requiring excessive cranking). May be a red herring.

Sure the oil could be overheated, but I wouldn't expect that without some general engine overheating. If you had an IR temp gun, the oil pan would be way hot.

Pressure needs to be checked with a mechanical gauge to see if the gauge or pump is at fault. I'm not sure of an easy way to do this on a 928.

vcompetello

Well thanks for the info. I ran back out and really took a good whiff and it smells like a gas station in there. I'm beginning to think the gague is off because upon closer inspection...all the gagues r off. At a full tank the gas gague reads just above 3/4. The voltage gague doesn't go past 13 volts at any rpm. But now I do have this oil in the gas problem. I'll change the oil, check the pcv and the list of other stuff you mentioned. Again, thanks for the help!!

Bill Ball

Oil contaminated wih gas also should feel and act differently. It will run more freely off the dipstick and drip more rapidly and feel thin. Changing the oil would temporarily remove gas contamination and at least rule that in or out. Maybe you're on to something with the instrument issue. Dunno. Maybe Alan has some ideas on that.

vcompetello

Is it possible that the piston rings would go bad?? I mean obviously anything is possible but what are the odds with this car?? I really wouldn't know what else would cause so much blow by.

Mrmerlin

Hi just a thought you mentioned that the 12 pin connector is clean, does that mean you took a rubber eraser and cleaned the contacts?, there might be a few other contacts that might be needing cleaning, as far as the gas in the oil smell I would think that either one of the fuel pressure dampers or fuel press regulator is bad to test just pull off the vacuum line to each one and apply vacuum and see if its letting gas come out of the vacuum port,and lastly it might be time to replace the injectors with a new set before this i would run a bottle or 2 of techroline thru the system.
As far as the oil it might be time to replace the oil thermostate in the engine, as well as the oil and filter, in fact i would say replace the thermostate and springs with the kit, good luck Stan