carman12

Before changing oil and filter, warm engine would produce 4.5 bar pressure at 5,000 rpm. After changing oil (same weight -- 10w-40) and filter, pressure would not go above a little over 3 bar. First, I suspected the oil filter bypass valve was opening. It was a Mann filter, which I had not used before. So, I switched back to a Baldwin, the brand which I have been using for years on this car.

Warm idle (950 rpm) is about 1 bar. Cruise (3,000 rpm) is 3 bar.

What could have made the change in oil pressure at 5,000 rpm?

Car is 1980 SC.

rstarga

Mann is the standard filter, I've never heard of a Baldwin. It might be too restrictive.

wildcat077

Stick with Mahle or oem and use 20w50 weight oil,your oil is too thin for an air cooled engine !

Cheers !
Phil

carman12

Been using Baldwin for years. Their market is mostly commercial vehicles. High-quality filters. Didn't have any oil pressure problem with Baldwin filters before.

Been using 10w-40 for years in this car. Had been using 20w-50 initially, but advised to change by local, reliable air-cooled-Porsche mechanic. No oil pressure problem before this oil change. Still looking for a helpful answer.

Caferacer

So you are using the same filter and oil you have always used and getting a different reading. Another variable is oil level. Would accidentally underfilling cause this reduced pressure? What kind of oil level reading did you get when you did your "fine tuning" drive?

ron mcatee

carman, what psrt of the country do you live?

carman12

Refilled with 10.6 US qts oil. Oil level is correct.

I live in the Pacific Northwest -- Portland, OR area.

Steve Weiner-Rennsport Systems

Hi,

Its most likely that one of your oil pressure relief pistons is stuck and will need to be removed and cleaned.

salukijac

Hi Steve,

Quick question for you and I hope I don't hijack the thread...so when the oil pressure gauge is fluctuating, almost like flickering, can that also be the pressure relief valve?

Steve Weiner-Rennsport Systems

Thats usually a sign of electrical issues: wiring, connectors, bad/intermittent senders and/or guages.

Once you know all that is just perfect, then remove and clean out the oil pressure relief pistons and passages.

dshepp806

Steve,

What's the best way to go about this? I do recall when I first got the '89, my son-in-law assisted with the first oil change,..of course he dropped the wrong point and pieces/parts few everywhere (learned the hardway-he did,...as I chided his ****' for months). I had my Porsche wrench check this out (behind us) a few weeks later while in on a valve adjustment,..and he found no problems with the reinstall......(thankfully!)

My question has more to do with "how" you would go about properly "clean-out" everything,..maybe some commentary on how this area "fails" (or becomes marginal or partial)..parts inspection particulars..piston integrity, wear traits, etc.

Sorry to bother you with the small stuff...as this "may" be related to proper oil pressure measurements, I'm interested.

Best!

Doyle