Car starts and idles as it should. At 10 minutes, it leaks oil. A lot.
Backstory…I’ve had the car for about four years. Ran like a top. Oil PSI has always been high, 65-ish and didn’t change with RPM. Last year I installed the 914werks oil sump extension, and replaced push tube seals and oil cooler seals. Ran it at Grattan in a first timers group. Car ran well all day, then on the last lap the oil PSI dropped to zero. Immediately powered down and called it a day. Couldn’t find any leaks, the oil level was right, and it started and ran as usual, so I chalked it up to a short in the gauge. A couple of weeks later it started leaking oil from around the oil filter/cooler area. Confirmed pressure with a mechanical gauge, still 65 PSI. Since then I’ve been chasing it, and have replaced the oil filter, oil cooler seals, oil cooler, a pressure relief valve (near the oil filter). Could it be leaking from the head or cylinder gaskets? Seems like it would be leaking all of the time then, not just at the ten minute mark. It’s not leaking from the pressure sensor port either. I run 20w-50.

Looking at the diagram, where is the oil cooler bypass piston, internal, in the filter bracket? If valve malfunctions, what happens?

This block does not have the second relief valve.

I’m going to get it up on ramps to get a better look while it’s running, but what do you think?Click to view attachment

The pressure bypass is under (above, actually) the big round slot-screw boss near the filter. It has a large copper (or al-loo-MINEE-UM) washer on it. It helps to have a large screw driver or slot driver (what's the tool called that you use on GM suspension?)

That boss/insert can be removed with oil in the sump, it won't lose oil.

You should replace it with Tangerine's relief valve:
https://tangerineracing.com/shop/ols/produc...re-relief-valve

Discussion here:
http://www.914world.com/bbs2/index.php?showtopic=236133

HOWEVER, that all said, it's highly unlikely to be a source of significant oil leaks. It's just a large machine screw, sealed by a washer.

Let me posit a random thought: have you recently removed the oil cooler flapper system? If so, did you know that the screw about which the pulley pivots goes into a threaded boss that is open to the inside of the engine? Not that I've learned that lesson myself the hard way (more than once...) - GA

65 psi at all times is excessive pressure. 10 psi per 1000 RPMs is the general rule of thumb. Wouldn’t expect 60+ psi until you’re spinning the engine past 4500+ RPM. What type of pump is being used? Type 1 pumps notoriously hard to seal and would be even harder if constantly pumping 65 psi.

Could be a loose galley plug with too much pressure behind it that needs some heat in the case before it gets loose and leaks. There are a couple of them up behind the oil cooler.

The part that makes no sense to me is oil pressure mysteriously going to zero and then coming back to 65 psi at all times. I’m at a loss on that one. If it truly was a wiring issue to the sender that ought to be investigated, otherwise it’s just a distraction to the root cause of your leak.

Did you pull engine to replace the oil cooler seals? Very easy to have them slip out of place when trying to replace them in vehicle.

Dupe