oldtin

My search-fu is failing me. 1986 928s (early one). It's taking too long to build oil pressure on cold starts - especially on an incline (nose up hill). Like 10+ seconds. What's going on - bypass valve, pressure relief valve??? It's got me pretty concerned.

Lizard928

What oil are you running in the motor?

oldtin

I'm going to butcher the name, but rotella 0-40 or 5-40 if I recall - I remember it wasn't particularly easy to find.

dr bob

Hmmm. 0W- or 5W-anything is thin as water. Consider using a grade of oil recommended for your car and your climate. 15W-50 or 20W-50 would be good choices. Brand is less important than viscosity.

Lizard928

Rotella 15w40 triple protection is good. But don't use anything thinner.

See if that makes a difference.

Mongo

If it's hot out and you have that thin of a grade of oil in the motor, your gauge won't register much oil pressure. 15w50 - 20w50 is what will get that gauge reading the proper numbers.

jthwan22

at cold start 0 weight is like water. When it heats up to temp then it becomes 40 weight.

dr bob

Common misconception, or maybe common mis-description. 0W-40: At 0ºC (32ºF), it has the viscosity of 0 single-weight. at 100ºC (212ºF) is has the same film strength and may have the same viscosity as straight 40 weight does at 100ºC. The oil does not get thicker as it gets hotter. The polymer chains keep it from thinning but don't cause it to get thicker.

oldtin

since I couldn't remember what it got for the last oil change it got 15-40 yesterday. Same issue - very slow to build pressure on a cold start. Instant pressure on a warm start.

Mrmerlin

did you also change the filter?
what filter did you install?
are the wire connections tight at the sender?
are the pins clean at the 14 pin connector and do you have a hot post cover?

oldtin

Didn't change the filter - no one had one in stock - will have to order, Pins are clean, wires are tight and there's a hot post cover. Not a sender issue - lifters make a little noise until pressure builds.

Lizard928

This really needs to be confirmed with a manual pressure gauge.
If indeed you aren't building pressure, then you need to replace the oil pump pickup seal to lower block

safulop

Do you have a leaky oil pan? I had this problem with dry-starting on a 944, which was solved by replacing the leaky oil pan gasket and rear main seal.

Mrmerlin

what filter is in the car now?
have you ever taken the oil pan off?

davek9

It's not the type of oil.
May I suggest u remove the oil sender and the check valve assembly above it (watch for the springs and note how it all come apart).
Clean out all the gunk and re-test, and agree that a real oil pressure gauge is the only way to know for sure, especially if you heare lifter noise.