Low Oil Pressure

[tstone]

Anyone have any experience in adjusting oil flow-pressure?
My M35 apparently has long term wear on the bearings; when the engine starts up I get about 35 lbs. at idle, after running for about 15 minutes it drops off to 3-5 lbs. at idle, this is all indicated on a mechanical gage. I get about 12 - 15 lbs. while running and shifting gears.
I have a gov. rebuild engine but have not made time to switch it out. Looking to make one last run for the Memorial Day parade in my hometown before I switch out the engine this season. I'd like to boost the oil flow to protect the bearings so I can have a rebuildable engine core.
I did the Tonka oil cartridge switch about 3 years ago, that has helped in getting oil to the bearings faster than the OEM system and has probably prolonged the engine life.
Any guidance will be greatly appreciated!

Thanks, Tom

 

[doghead]

There is an oil pressure regulator on the side of the block. It controls both the turbo and the engine oils separately.

It may simply need cleaning/servicing.

Should be covered in the -20TM.

 

[cranetruck]

Low oil pressure in my multi turned out to be a clogged pick-up screen. Ran on veggie oil and biodiesel for years and some found its way into the crankcase and created problems.
Don't load the engine with low oil pressure!

 

[59apache]

thinned motor oil is maybe the problem... do you have the same readings with new oil and filters?

 

[m-35tom]

you may be able to clean the pick up screen through the drain plug hole, but straight 50wt oil may be the only way to get more pressure if wear is the issue. always check your gauge with another quality gauge just in case. how noisey is the engine when it is started after sitting??

 

[m-35tom]

thinned motor oil is maybe the problem... do you have the same readings with new oil and filters?

maybe fuel in oil??

 

[seano11]

A jug of Lucas should fix the problem

 

[DieselBob]

I was thinking that same thing. Any evidence that you are getting diesel fuel mixed in the motor oil and thinning it or is this with fresh oil.

 

[m-35tom]

There is an oil pressure regulator on the side of the block. It controls both the turbo and the engine oils separately.

It may simply need cleaning/servicing.

Should be covered in the -20TM.

turbo and engine oil are the same and controlled by the same valve. piston cooling is the other and it opens at 15 psi so there is no oil to pistons at idle to improve oil pressure.

 

[jamawieb]

Check for fuel in the oil. I had the same problem, good pressure when started but after it got warm, the pressure would drop to 3lbs. Finally found that the booster pump seal went bad and was leaking fuel into the crankcase. Hope this helps.

 

[jatonka]

You can add a shim washer to the external oil pressure regulato on the side of the block behind the turbo. There is a pressure regulator in the oil pump too, but the external reg is easier to get to. If you drop the pan to clean the pickup screens, that would be the time to read the manual on the oil pump pressure regulator and adjust oil pressure accordingly. JT out

 

[welldigger]

Which TM specifically covers the adjustment of the oil pressure regulator? I have yet to figure out exactly how to navigate them. I found the trouble shooting guide but that's as far as I got.

 

[maahes]

Is there a TM that has what the optimal oil pressure should be?

After a few oil changes my oil is no longer black sludge. At cold idle the gauge (120lb) shows 60, but at warm idle (160deg) oil pressure is around 30, goes back up to 60-80 with the go pedal down. I know the pressure will change depending on RPM, just want some numbers on what's too low.

 

[Amram]

My truck starts up and oil pressure sits around 27-30 psi when running it is about 35psi. Do I need to do this oil pressure regulator adjustment on mine as well?

 

[shenkmen]

Is there a TM that has what the optimal oil pressure should be?

After a few oil changes my oil is no longer black sludge. At cold idle the gauge (120lb) shows 60, but at warm idle (160deg) oil pressure is around 30, goes back up to 60-80 with the go pedal down. I know the pressure will change depending on RPM, just want some numbers on what's too low.

Yes, there is a TM for this info. I don't remember which one or the acceptable oil pressure range. Both are posted in many threads on this site. I want to say it is a minimum of 10 PSI but don't go by that.

 

[orren]

You can add a shim washer to the external oil pressure regulato on the side of the block behind the turbo. There is a pressure regulator in the oil pump too, but the external reg is easier to get to. If you drop the pan to clean the pickup screens, that would be the time to read the manual on the oil pump pressure regulator and adjust oil pressure accordingly. JT out

Just exactly where do you put the shim washer to increase the oil pressure. There are two springs
in the external regulator. Also, about how thick does the washer need to be?

Thanks for your help,
Orren

 

[JasonS]

Just exactly where do you put the shim washer to increase the oil pressure. There are two springs
in the external regulator. Also, about how thick does the washer need to be?

Thanks for your help,
Orren

This only works if you are exceeding the bypass valve pressure. Why don't you fix the engine before it blows up?

 

[Jeepsinker]

Could have a piston cooling jet broken off which would bleed off a lot of pressure once the regulator opened flow to the jets....

 

[orren]

Could have a piston cooling jet broken off which would bleed off a lot of pressure once the regulator opened flow to the jets....

My oil pressure has for years run up to around 30 lbs. max. Is this really enough
or should it be higher, especially if truck is under heavy load.

For now let's assume the cooling jets are OK even if my LDT-465-1D has them, is
there a way to get more oil pressure by only adjusting or shimming the springs in
the external regulator?

Thanks for the help,
Orren

 

[JasonS]

Just exactly where do you put the shim washer to increase the oil pressure. There are two springs
in the external regulator. Also, about how thick does the washer need to be?

Thanks for your help,
Orren

According to TM9-2815-204-35, the oil pressure regulator valve opens at 40 psi. How will shimming this to open at a higher pressure increase your operating oil pressure?