High oil pressure

[k hutchins]

Hey everyone
I know this is a recurring subject, but l've searched several threads and need more specific direction or information.

My main mowing '48 Cub has perpetually high oil pressure. At start up it pegs all the way to the left on the guage. After it warms up, it with drop to 3/4 when at low idle, but when l throttle up it pegs high again. This is causing oil to seep out around the filter gasket. I thought initially that it was a rear main seal leak and even ordered a new seal from TST, but while prepping to split it l found that the leak is seeping from the filter housing.

The research leads me to the pressure relief valve, but here is my question. When disassembling/removing the valve and spring, (yes l saw the dowel rod technique), is it sufficient to just clean up the valve and tube or do l need to replace the spring? The valve head (for lack of better terminology) is not available from TM, Steiners, or Hamilton Bob's.
Is the valve most likely what's causing my issue or is there possibly another cause l am unaware of?

Any and all information is appreciated, thanks in advance

Hutch

[Don McCombs]

http://www.tmtractor.com/new/en/671fp.htm
http://www.tmtractor.com/new/en/537fp.htm

In addition, I would use a rigid paper gasket for the oil filter cap instead of the slippery rubber ones. Your cap may also be distorted from over-tightening.

[JimCub48]

You may also want to check your guage, that could also be your problem. The leak around the oil filter cap is a separate issue, bad gasket, bent warped cap, bad or no bolt washer?

[inairam]

What weight oil are you using?

[Jim Becker]

Proper oil pressure (by the specs) is 30 to 35 psi with the engine up to speed. You should see this with a fully warmed up engine. Higher readings on start-up are not unusual or necessarily a problem. If after all the considerations others have already given are investigated, you could have a pressure regulator problem. The valve needs to be able to move smoothly in the engine block without catching or binding. It isn't very fussy otherwise. If the valve is worn (an unlikely problem), the effect would be loss of pressure rather than an increase. I stuck valve could cause an increase. The spring should have a free length of 2-31/32 and a length of 2-15/32 with 9-1/2 pounds of force. Measuring under force may not be easy for you, but the free length is a good first indicator. In general, ANY SPRING will become weaker with age rather than stronger. Thus a bad spring will generally make the pressure lower not higher. So again, the pressure relief valve is an unlikely source of your apparent oil pressure problem.

[Eugene]

The research leads me to the pressure relief valve.

To remove the valve, providing it is not stuck in the bore - - remove the cap and spring. Replace the cap, start tractor. Valve will have been pushed to the back of the bore, next to the cap, and easily removed.

Folks have added shims/spacers or replaced with a heavier spring, thinking this would increase oil pressure.

[k hutchins]

Thanks everyone.
Jim, the valve is out of stock at TM.

To everyone else. Ishould have said l'm running 10w30 non detergent non synthetic. Them same thing l've run in my original '48 for 50+ years without an issue. I may have a rubber gasket instead of the paper due to changing filter brands. I have a different cover from JP that l bought a couple years ago. I'll swap those out to see it it makes a difference.

Eugene, if l understand how this works. If the valve is stuck, that would cause the high pressure? If l use your suggested method of removal and it pushes back to the cap, it's not stuck, correct? If it's just a weak spring that would give me low pressure?

Thanks for the information/responses everyone.
As l've said before, l can do mechanical things but l'm not a mechanic.

[Clemsonfor]

Running non detergent oil you may have some sludge issues. This engine with its filter oil system really should of been running detergent oil to hold any crud in suspension untill the filter could catch it.

What you said is correct according to what Eugene posted. A weaker spring from his explanation gives you lower oil pressure because it can't hold the pressure as it should . The worn spring would grow in spring length which would lower its oil pressure.

[k hutchins]

Thanks Clemsonfor for the clarification.

I believe l've fixed my leak. Swapped covers and new unused gasket initially and it went from a drip to a waterfall. Swapped out for a different cover, same thing. Stole a gasket out of a napa filter on my shelf, no more l drips.
It's still running high pressure with the needle just barely inside the white at the left side, and it doesn't move or wiggle at high or low rpm idle. I did run it long enough for the engine to warm up after fixing the leak. Still no change.
Because l'm ignorant, can someome post a picture or diagram showing where the regulator valve is? I thought l knew, but what l thought was it is too small of an orfice, so obviously l'm wrong. I checked 4 different owners manuals from '47 to '72 and they all say contact your dealer. I'll check the resources on the forum before l sign out, but any other help would be appreciated.

[Jim Becker]

. . . l'm running 10w30 non detergent . . .

I don't think such a thing exists. Re-read your oil bottle and tell us what the API classification is. It should be 2 letters starting with an "S".

. . . It's still running high pressure with the needle just barely inside the white at the left side . . .

This is the second time you have said "left" where I think you should have said "right". You do know that the left side of the gauge is the zero end and where the needle should point if the engine is not running?

[k hutchins]

You're correct, my miistake, l meant right.

I'm using TSC Traveler conventional 10w30 API SP

[k hutchins]

Disregard the request for a picture to locate the pressure valve. I found the correct pdf file. I'm going to order a new spring just in case, maybe a new guage as well.
At this point since l fixed the leak, l can wait until mowing season is over to do other repairs.

Thanks again to everyone who responded with information. It was greatly appreciated.

[Don McCombs]

If you find you need a new valve and it’s still out of stock at TM, try Messick’s. They appear to have them in stock.

[Jim Becker]

I'm using TSC Traveler conventional 10w30 API SP

That is the most recent spec for spark ignition engines. It is a detergent oil. You can disregard or at least reduce concern about any suggestions that assumed you were using a non-detergent oil and have sludge build-up.

[cdahl383]

Mine pegs out when cold but once warmed up it's in the 1/3 to 1/2 position usually. I also had a leak from the oil filter cap, but out of the top from the bolt. I ended up using a nylon washer for a 1984 Chevy Camaro between the bolt and oil filter cap. Cured my leak.