Hi - I just completed my first oil change and am now experiencing low oil pressure. Must have done something wrong and could use some help.

Reviewed the P-car DIY oil change this morning.

Conducted change later in the day on my 96 C2 Tip, 25k miles.

Drained tank, changed big and small filters, removed and adjusted oil tank gauge, replaced gauge (seal looked good), opened 17mm plug assembly at center front end of engine assuming it was the crank case drain, some oil came out of this port. Did not drain crankcase (15 mm plug). Added 10 quarts of 15W-50 M1.

Started engine, oil pressure was slow to come up (took perhaps 20 seconds), stayed around 1 bar at idle, checked for leaks, checked dip stick (full), drove car for about 10 minutes, oil pressure came up to about 3 bars at 3K RPM. (Pre-change oil pressure would have been at 5 bars at 3K). Pressure then dropped below 1 bar at idle and oil light came on. Brought revs up and light shut off. Idled again and light came on. Shut down. Re-checked for leaks and found none.

Other than opening the 17mm plug and not draining the case, everything seemed to go well.

Any thought? What is the 17mm plug assembly? Seems like it was pressurized slightly when I opened it. Engine has not been brought up to normal operating temperature at this point, but I plan to not operate without some feedback. Thanks in advance for help on this.

-Bob

Bob, I think you are right to be concerned. It has been a long time since I did the oil change on my car but it sounds like either your new oil is too thin or somehow you have disturbed the operation of the oil pressure relief valve.

They are the only reasons (that I can think of) that would give such a marked drop in oil pressure after an oil change.

Have you checked the level since the 10 minute drive?

I hope someone with more oil change experience answers too but I thought I'd chip in, GOOD LUCK.

I think you may be right. I did a little further digging and confirmed that the 17 mm plug I removed is the pressure relief valve. The spring probably fell into my waste oil drain pan and I missed it. The pressure is probably low due to the missing spring/open relief valve.

Look for a small steel ball too.

Once you put them back all should be back to normal. Fingers crossed!

Look up diags 101-05 and 101-10 in PET6, 'Main Group - Engine' ... and the two crankcase oil relief assemblies are illustrated in their correct orders .... so which one looks familiar?
Good luck fishing in the waste oil bucket!

Thanks Garth, so the spring pushes on a piston not a ball, most likely the piston did not come out of the housing.

Good news Bob, looks like you only have one thing to find in the old oil.

After an oil change I pull the DME relay and crank the engine until the oil pressure gauge starts moving. I then reinstall and fire it up. Another Rennlister, Mike, made this recommendation.

Thanks guys. Great info.

Looking forward to fishing for the missing spring.

If I crack the pressure relief valve plug with the oil tank full, will oil from the tank flow back?

I'm assuming that under an over pressure situation that oil circulates through the valve back to the tank. The affected valve is the one near the transmission, just below the small oil filter.

Thanks everyone. Found the spring and piston in the waste oil pan. The tank drained when I pulled the pressure relief plug but was prepared with a 5 gal pan. Re-assembled the relief valve, refilled, pulled the DME relay and cranked the starter. The pressure almost immediately came up to 3 bars, and reached 5 bars at start up. The tank gauge calibration looks pretty good. Read empty before at mid point on the stick twist. I bent the float bail about a quarter of an inch.

Bob, good to hear that all is well and the oil pressure is back where it should be.

These Porsches are toughest beast in the world!!!!

Just remember all the drain plugs are 15mm.