Engine/Transmission (1994 - 1998) Oil pump bypass valve??

[JGheen]

Is there an oil pump bypass valve on these engines?



I am still trying to figure out this oil filter leaking on cranking but not on start-up/while running issue and I am now thinking if there is an oil pump bypass valve that could possibly be sticking, it could be creating a huge oil pressure spike on start-up. Is this possible?



Thanks, Joe

 

[Mundgyver]

Which truck are you referring too and define spike please. On my truck when I start up I usually have 80 psi until things get warm and then it settles in a 58 to 60 psi on the freeway and 25 to 30 at idle.

 

[JGheen]

Talking about the '98 12v.



I am thinking if there is an oil pump bypass valve that may be sticking, it could be the reason I am leaking oil past my oil filter seal on cranking but not while engine is running. Possibly causing a pressure spike beyond the filter seal's "sealing" capability making it leak until the pump starts being driven by the engine fast enough to "un-stick" it.

I too had always got about 80 psi or so on starting the engine when cold and around 50-60 while driving.



Is there another spot on this engine where I could put a mechanical oil pressure gauge other than the 1/8" NPT port on top of the filter housing? Has anyone put a T into the port where the dash sensor is on the side of the block?



Joe

 

[Mundgyver]

Look at the oil filter assembly. I thinking yours will be like mine. To the right side you will see a bolt head (kind of large) sticking up at about a 30 degree angle. Under that bolt head is a spring and ball, that should be your pressure regulator. The it is closed, (ball is fully seated) you get maximum pressure, the spring should open at about 65 psi.



When I added a bypass system to my truck, I increased my pressure by installing a very thin shim between the bolt head and the spring, thereby causing it to have more tension required before the ball would open. I gained about 6 psi in pressure.



I would suggest to clean it first and see how that does before making any changes.

 

[JGheen]

Already had the filter assembly apart and replaced the oil cooler with a new one I had sitting around, new filter bypass valve, regulator piston and spring. I posted this in another thread about questioning the use of the filter bypass valve for a truck that is strictly a sled puller and no one responded to my findings after my R&R, so I thought there was possibly a oil pump bypass valve but after researching more I found it is just a gear driven planetary that uses the relief/regulator valve in the filter housing for the bypass.

Guess I am on my own on this one as nobody has any answers for me. Right now I am thinking there is a crack in the filter head somewhere. Going to take it all apart again and try a new head casting which is the only other possible faulty part. I highly doubt Fleetguard has a bad batch of filters going around with faulty seals, I am sure others would be complaining as well.



Joe

 

[Dieseldemon]

There is a bypass valve inside the housing where the oil filter mounts if you take the mount off you will see the valve about in the center of the hsg. Hope this helps