Low Oil Pressure Reading 75 1.8

Ray Morgan · 07-14-2003, 06:18 PM

My idiot light keeps coming on. At idle (900 rpms) to 1800 rpms the light will remain on. I have replaced my oil pressure sending unit.

I am also taken a true oil pressure reading with a compression guage -- 9 lbs at idle.

Unfortunately, inside the hole where the sending unit sits, the threads are slightly stripped, so the compression guage didn't fit quite right.

Any suggestions for a solution to the low oil pressure reading? Any idea how to thicken the shaft of the sending unit? Will a sealant work on something like this?

Ron Meier · 09:34 PM

you can try retapping the hole a little larger and put heavy grease on the tap to capture the cuttings - and go slow. Then with oil in the engine turn it over with the sensor out and let the oil flow up and out to clean the hole = messy, but you might avoid metal in the oil galleries.

or

clean the hole with brake cleaner and the sensor threads too. run JB Weld epoxy around the threads on the sensor (not on the end, screw it into the hole and put more JB around the top at the block surface. If the JB takes on a clean surface, I doubt you will pull the sensor again, but it prolly won't leak.

Ray Morgan · 07-15-2003, 01:44 PM

Well, I used some liquid teflon to coat the threads of the sensor; when it hardened/dried I reinstalled the sensor, with a copper crush ring as a washer. I'm still getting the low pressure reading. I don't know if I truly have low oil pressure -- the car seems to run fine.

What about oil coolers, oil pump, etc? I'm a novice mechanic -- good at following directions in my Haynes guide, but not much else, and I'm sort of learning as I go on 914s.

Basically, what else causes low oil pressure? Could there be a glitch in the wiring? Where does the wire come from that connects to the end of the sensor?

Sorry if all of this is remedial mechanics for you guys -- I'm just way too new at 914s to figure this stuff out.

Ron Meier · 07-15-2003, 02:16 PM

1. Pressure relief springs to weak or pistons worn ( 2 on case - See Haynes).

2. Severly worn bearings

3. Worn out/leaking oil pump

4. Leaking oil gallery plugs on back of case

5. Poor voltage to idiot light

That's about all I can think of.....................,

Ray Morgan · 07-15-2003, 02:44 PM

With worn bearings or pistons, will I see any "symptoms" during performance? The car runs great -- never a loss of power, never dies, or idles unevenly. Lately, however, I have noticed an occasional puff of white smoke out the exhaust.

Ron Meier · 07-15-2003, 03:17 PM

Puff of smoke on deacceleration = bad guides or worn rings
On acceleration - blowby due to worn rings

With worn bearings it would be lo oil pressure, not necessiarliy knocking in the engine. Should not adversely effect running that you would notice.

Sounds like a high mileage engine with a top end refresh at some point.

Ray Morgan · 07-15-2003, 03:20 PM

The smoke is definitely on acceleration, or high RPMs. So, you're thinking worn rings? Would this have anything to do with low oil pressure? Or did low oil pressure cause this problem? Or are these two problems unrelated?

The engine was rebuilt about 2 years ago -- the odometer stopped working at some point, but we estimated less than 3000 miles since the rebuild.

Ron Meier · 07-15-2003, 03:49 PM

Blowby (worn rings) will pressurize the internal block, pushing aerated oil up into the breather(s) which are connected to the intake system. It will then be sucked into the cylinder and burned producing white smoke.

High RPM will froth the oil and create much the same condition as blowby.

Do a compression check or pay someone to do a leak down test.

Neither of these will cause a lo oil pressure condition.