Oil pump effectiveness as it ages

[Trav]

Most engines today use a gear rotor crank driven pump, older engines mostly used the double spur gear pumps either in the pan or from cover.
The difference was not gear hardness but housing hardness, cast iron wore less than aluminum housings.

Front cover types were almost universally aluminum housings for some of these hardened stainless inserts were sometimes available along with longer spur gears, spacers and modified cover and relief valve.
Getting good oil pressure and flow with some of these old gear pumps could be a real challenge, brand new some engines has less than 10psi at hot idle and max of about 40 psi using 10w30.

 

[groomerz]

I purchased my kid a lexus es300 with 140k miles had flickering oil pressure light and found problem was clogged intake screen on oil pick up. It appears that it had some sludge and some silicone sealant from a previous valve cover gasket repair. So low oil pressure can be caused by restriction in suplly of oil to pump. Like sucking on a creased straw

 

[meep]

older Subaru crank-mounted pumps had a habit of backing off the screws to the front plate. Once tightened they would come right back to where they should be.

Never seen a pump wear out in my experience. Usually the bearings would wear elsewhere relieving pressure if there was a problem. Most of the time I think oil pumps spend their hours with the relief bleeding off excess flow/pressure at normal cruise RPM. they pump a lot more GPM than you'd expect.

The only variable displacement pump I've looked at closely is the pentastar V6. And it really isn't gradiently variable, there's just a solenoid valve that opens and closes a relief, much like a 2 speed home HVAC compressor.

-m

 

[Trav]

Originally Posted By: meep
Most of the time I think oil pumps spend their hours with the relief bleeding off excess flow/pressure at normal cruise RPM. they pump a lot more GPM than you'd expect.


You probably don't have much experience with spur gear pumps then. When I first started out we were changing GM oil pumps because brand new they were only making 7 psi at hot idle and max 35-40 psi at 4,000 and up, hardly in relief.
The revised pump wasn't much better. I use to do a lot of Buick engines and did so many pumps I can still do one at night by feel, lots and lots of failures.

It got so bad starting with IIRC the 430 Buick in 69 GM put a fuel shutoff circuit into the oil pressure sender circuit on cars like the Riviera with an in tank electric fuel pump so if the pressure dropped below a safe level at idle it shut the fuel pump down.

Chrysler slant 6 had problems with soft spur gears and breaking pump drive teeth, I did a few of those and dozens more of many makes. Newer cars are no immune either..

http://www.carproblemzoo.com/hyundai/sonata/oil-pump-problems.php

https://ls1tech.com/forums/generation-iv-internal-engine/1758563-20k-mile-ls3-oil-pump-failure.html

http://www.gm-trucks.com/forums/topic/171018-oil-pump-failure/