I bought my 73 914 1.7 in April. Car runs great, compression is in spec. After rebuilding the carbs and adjusting the idle I started getting the oil pressure light at idle once the car was good and warm. I even turned up the idle speed to stop this but then I was idling at 1200rpm. I am running Valvoline VR1 20W-50.

After researching low oil pressure here, I installed a VDO gauge and sender using the "remote mount" grease gun hose and a tee so I could also use the idiot light sender. I was hoping to see about 10 psi per 1000rpm but the gauge confirmed that the pressure was low. After warming up the engine I was seeing about 15 psi at 3000rpm and almost zero at idle (and the pressure light was coming on just as it had been.)

So digging in a bit more, I replaced the oil cooler seals because they were leaking (just some drips on the garage floor, nothing major). I also took out the primary pressure relief valve just for giggles, cleaned it and put it back. Now I have everything back together and I go out for a drive... Low and behold I have oil pressure!

I'm running 40 psi while driving and it drops down to just above 10psi at idle. Couldn't believe my eyes so I drove it more to make sure I was at operating temp. Still no problem, good on the gauge and no oil light. I was able to set the idle back to 800 rpm and still no problem.

What would have changed? Would a leaking cooler seal cause this? Glad to have pressure again but always curious about root cause.

My Guess:
The plunger (piston) in the oil pressure relief valve was stuck.

There are a few threads around here that discuss that a ridge will develop inside the bore of the pressure relief valve.
Your piston got stuck beneath it.

A few here have actually honed the bore to remove the ridge.

Stu

Good guess, I tend to agree. When I put the plunger back in and pushed up with the spring and cap it stopped and then popped up in further. Could have been that I broke through the ridge. Drove again this morinign and pressure still looks great!

Maybe an old seal swelled into the oil passage, or flow through the cooler improved too. Glad it stopped doing that!

worn,

Wasnt it your thread where you reamed out the lip in the relief valve bore?
I tried a search to find it, but gave up easy.

Stu

http://www.914world.com/bbs2/index.php?sho...l=oil++pressure