LS170 oil pressure drops and then returns

[dfarmer]

Just found this forum and hope you can help. 844T engine and oil pressure at 60 psi and then will drop to 40 and then return to 60 but will sometimes drop to "0" pressure and then jump back to 60. This is with pressure gauge in place of idiot sender at front of head or in the oil gallery on left side of engine. Changed oil and filter, checked oil pressure relief valve. Any suggestions before I pull the motor? About 3200 hours and runs fine otherwise. Thanks Dale

 

[antfarmer2]

I would check the oil pressure relief spring weak or broken

 

[frogfarmer]

The oil cooler at the filter can get clogged with debris from the engine coming apart or possibly sludge and cause this type of symptom. Also the pumps have been known to break the stationary shaft the pump elements run on resulting in low or no oil pressure. If the bearings are worn or failing it may be passing enough oil through the system to starve the pump but in this case I would suspect you to have a noticable knock.

 

[dfarmer]

The oil cooler at the filter can get clogged with debris from the engine coming apart or possibly sludge and cause this type of symptom. Also the pumps have been known to break the stationary shaft the pump elements run on resulting in low or no oil pressure. If the bearings are worn or failing it may be passing enough oil through the system to starve the pump but in this case I would suspect you to have a noticable knock.

Thanks for the replies. Antfarmer2-Ordered a new oil pressure relief valve on Wed. was to ship from warehouse on Thur., not here yet. Took the regulator cartridge out yesterday, piston moves smoothly in bore under heavy spring pressure. Don't see how this could open enough to let pressure drop to almost zero. Frogfarmer-will pull the oil cooler off this morning and check for intermittent blockage. Engine is clean inside valve cover, change 10w-30 rotella and filter every 100 hours. When running yesterday, holds 60psi then drops to almost 0 and then returns to 60. Very disturbing!!! The port block has to be removed to replace the pump shaft? Thanks-Dale

 

[antfarmer2]

Thanks for the replies. Antfarmer2-Ordered a new oil pressure relief valve on Wed. was to ship from warehouse on Thur., not here yet. Took the regulator cartridge out yesterday, piston moves smoothly in bore under heavy spring pressure. Don't see how this could open enough to let pressure drop to almost zero. Frogfarmer-will pull the oil cooler off this morning and check for intermittent blockage. Engine is clean inside valve cover, change 10w-30 rotella and filter every 100 hours. When running yesterday, holds 60psi then drops to almost 0 and then returns to 60. Very disturbing!!! The port block has to be removed to replace the pump shaft? Thanks-Dale

Hope it works I see tazza rattling around here hope he chimes in

 

[frogfarmer]

Thanks for the replies. Antfarmer2-Ordered a new oil pressure relief valve on Wed. was to ship from warehouse on Thur., not here yet. Took the regulator cartridge out yesterday, piston moves smoothly in bore under heavy spring pressure. Don't see how this could open enough to let pressure drop to almost zero. Frogfarmer-will pull the oil cooler off this morning and check for intermittent blockage. Engine is clean inside valve cover, change 10w-30 rotella and filter every 100 hours. When running yesterday, holds 60psi then drops to almost 0 and then returns to 60. Very disturbing!!! The port block has to be removed to replace the pump shaft? Thanks-Dale

Yes the port block, shaft, pump elements, and the idler gear are an assembly. The shaft can be replaced but I don't think you can buy it separate. Also I don't believe there is any way to replace it without engine removal.