993944S2

86 944 Turbo
130K miles

I just noticed this morning that my oil pressure light was flickering at idol. It's also not above the #5 where it normally is. The light does go out as I accelerate but it does not go to the top of the gauge as per normal. Does this sound indicative of a big problem, or a sensor?

Thanks;

Don

mytrplseven

Check oil level, then consider a faulty oil pump or oil pump drive off the crankshaft; oil pick-up tube in the crankcase may be cracked; #2 rod bearing worn out or improper oil weight. Typically 5W-20 for higher mileage engines (dyno oil).

konakat

Sensor problems tend to be all or nothing, so it is probably a real issue. If you recently got an oil change, they may have used too thin an oil. If not, overfill the oil by a quart to make sure you have enough. Make sure the main crank pulley bolt is tightened to 155 lb-ft, if not the oil pump drive gear can slip.

993944S2

Thanks. Oil was not recently changed. It's currently filled just over the top mark. I'll check the main crank pulley bolt. I'm guessing it's prudent to get the car towed home.

konakat

That's the safe option, especially if the flickering is happening on a cold engine. It will only get worse as it warms up.

993944S2

If the oil pump drive gear has slipped, is it simply a matter of tightening the crank pulley bolt?

konakat

Yes. It isn't splined, just held on by friction. Be careful with torquing that bolt, if you don't have a flywheel lock then 155 ft-lbs is easily enough to move the rear wheels.

Tiger03447

Pull out the pressure sender and hook up a mechanical gauge...If it's a real problem, that'll tell you for sure. Maybe the sender is wonky..

993944S2

Thanks for all the suggestions. I just finished rear wheel bearings by myself in my garage. I'm not tackling this one on my own. I dropped it at the shop this morning. I'll report back. thanks again.

mel_t_vin

Don, what brand/type/viscosity oil are you running?

How often do you drive your car? When was the last time you had it out and noticed that the pressure readings were normal?

993944S2

Hi Allen;

Last change was Mobile 1, 5W-50. (I think....) It's not driven very often. I had just finished changing rear wheel bearings. The car was nose down, on jack stands for about 4 weeks. I noticed the OP light flickering basically on the first day of driving after the bearing change. About 15 minutes into the drive.

Update. Car is at the mechanic. They took an OP reading using their mechanical gauge and things look ok. Light is not on, but dash gauge still reads low. They are going to change a pressure relief valve and see if it makes a difference. They are comfortable with me driving it.

Thanks.

mel_t_vin

Don, both Mobil 1 5W-50 and 15W-50 [my flavor of choice] have high Zn content [good] and respectable high temp/high shear properties [good]. Either selection should result in solid cold/warm oil pressures. For reference, I see 4+ bar at cold idle and 2-3 bar at warm idle, depending on ambient temps.

If the light is not on and a mechanical gauge shows pressures to be in spec, the low reading on the gauge could simply be due to resistance [voltage drop] in the electrical connectors and/or wiring going to the dash.

The OPRV [oil pressure relief valve] in your '86 is the older, 3-piece, housing-spring-piston design. Shouldn't hurt to swap it out for a known good one.

Let us know how things turn out.

odonnell

I have two good OPRVs that are compatible with you car if you need one, not asking an arm and a leg.
Has the shop cleaned the grounds?

993944S2

New pressure relief valve and everything seems to be fine.. Thank you to everyone. Rennlist community is fantastic.

konakat

Awesome. That's pretty much a best case scenario, short of a loose crank bolt.