oil pressure sending unit

[jak133]

Hey all, been having problems diagnosing oil sending unit. Just put new one in and is doing same thing, when I first start the GT I get 2-2 1/2 bars then it slowly drops to 0. When I down shift i get the same 2- 2 1/2 bars then drops. I dont know what grade of oil is in it, could lower viscosity oil cause this? Any advise would be appreciated. And by the way the sending unit is oem from OGTS.

thanks joe

[wrench459]

Hey Joe

I see you've been having some issues with the oil pressure for some time now.
http://www.opelgt.com/forums/1e-othe...ure-gauge.html

Have you installed a known good mechanical gauge yet? I know its a pain but we need to narrow things down some.

[jak133]

Yes, have had mechanical guage on it. It read around 5 PSI at idle and 25 at around 2500 to 3000 rpm. Put new alt on today and resolved a lot of what i thought was grounding problems, but this sending unit is driving me crazy.

[markandson]

I don't know what PSI the oil pressure should be.....but from the symptoms it sure sounds like a bad oil pump or relief valve, probably the pump. You are getting too much oil recirculating within the pump, except when the oil is cold the viscosity is high enough to deal with the clearance issues. When you hit the gas the flow goes high enough to do the same thing and bring your pressure up. A work around would be to run heavier oil or dump some STP in crankcase, but the right way to do it would be to rebuild the pump. JMO

[wrench459]

Your oil pressure is very low.
With an hot engine o/p should be around 20-28 psi@idle.

[jak133]

Thanks for answers. Going to hook up mechanical guage again to confirm readings, if all checks out will look into pump.

[bello]

Hi! I read 2 things in your paragraph- probably a high mileage motor, perhaps under maintained? Probably the plastic piston and its seat are worn and bypassing oil resulting in low readings. I would start with a new oil pump cover/pressure relief valve- be careful when taking off the old one- the gears love to fall off: hold them together when you take them off the housing and put a "timing mark" on them so they go back in exactly the same relationship they had. Make sure the new pump cover is installed with the hex plug facing the back! of the engine. This will give you a nice boost in mid and high rpms, very little at idle. The second, less desirable problem is that your main bearings are worn and leaking oil, resulting in low pressures. I have seen the symptoms you describe- down shift=more revs, oil pressure rises= worn main bearings. Start with the cover and run a 10w-40 or even a 15W-40 motor oil. Good luck! Ernie Bello

[Bill Hoffmann]

The plastic plunger may indeed be worn, but also the plunger spring wears and loses tension. You may be able to see the thinning in the coils. Replacement of both is best, but you can also shim the spring to increase the tension. A shim could be a nut or ball bearing that fits in the hole behind the spring. While not a proper fix, it may get you by for a while and help narrow down the problem.

Bill

[tekenaar]

Originally Posted by markandson Originally Posted by jak133 Hey all, been having problems diagnosing oil sending unit. Just put new one in and is doing same thing, when I first start the GT I get 2-2 1/2 bars then it slowly drops to 0. When I down shift i get the same 2- 2 1/2 bars then drops. I dont know what grade of oil is in it, could lower viscosity oil cause this? Any advise would be appreciated. And by the way the sending unit is oem from OGTS. thanks joe I don't know what PSI the oil pressure should be.....but from the symptoms it sure sounds like a bad oil pump or relief valve, probably the pump. You are getting to much oil recirculating within the pump, except when the oil is cold the viscosity is high enough to deal with the clearance issues. When you hit the gas the flow goes high enough to do the same thing and bring your pressure up. A work around would be to run heavier oil or dump some STP in crankcase, but the right way to do it would be to rebuild the pump. JMO

. . . with my '69 Kadett my first time at Carlisle a few years ago AND because it's much easier to check quickly, I'd check the OP relief valve first!

After driving 1400+ miles from Texas without any problems on 10W40 oil and registering at the hotel, Gil asked for a ride to the event exhibit where I had yet to register in any case. Halfway or so there, the oil pressure dropped significantly - Rallye gauges - after stopping at a stop light. Like yours, I could raise it by revving the engine a bit.

Long story, short - registered, took car to the field and decided to check the OP relief valve first because it was the easiest thing to do - remove one hex nut and the relief valve and spring are easily accessible! In my case, a steel ball in the timing cover side (early version) - in your's, a nylon/plastic bullet shaped sliding plug in the OP cover (late version).

After removing the hex nut and spring from the OP relief valve passage, I found I couldn't retrieve the steel ball relief valve . . . oil viscosity surface tension in a slightly downward-angled passage. After no luck finding a magnetic wand, Rob offered one from one of the many "parts" vendors there.

Retrieved the ball and found a tiny piece of broken-off thread adhered to the surface of the ball, which kept it off the seat enough to "bypass" oil in the pump all the time . . . ergo, low oil pressure, especially noticeable at low revs!

Regardless of "early" or "late" OP relief valve, any irregularity on the "valve" or its seat that interferes with it sealing completely, will cause a constant "leak" there with a resultant low oil pressure!

[AZManta]

Originally Posted by jak133 Hey all, been having problems diagnosing oil sending unit. Just put new one in and is doing same thing, when I first start the GT I get 2-2 1/2 bars then it slowly drops to 0. When I down shift i get the same 2- 2 1/2 bars then drops. I dont know what grade of oil is in it, could lower viscosity oil cause this? Any advise would be appreciated. And by the way the sending unit is oem from OGTS. thanks joe

There is some very good information posted here, with one omission. When reassembling the pump assembly pack the gears with grease to hold them in place and to prime the pump. Failure to do this will result in zero oil pressure as the pump will not self-prime.

[jak133]

OK OTTO, I am a litttle ignorant when it comes to fixin vehicles. ( actually going through auto tech school now, but they typicaly cover newer vehicles) if you could show me where to look and what to do I can probably do the fix you are talking about. If it matters at all the car runs great no noises to suggest anything abnormal in the engine. Thanks for all your replies for $120 bucks a new oil pump rebuild kit wont hurt. Gotta love messin around with the older cars, the young kids in my class think this is the coolist car ever.

[Bill Hoffmann]

This is what the late version looks like (on a Manta).