H Oil Pressure Problem

Doug Kieta · Feb 20, 2017

When I first start my 51H, the oil pressure is 60psig. After a lengthy run, it drops to 10-20psig. Today I removed the oil pan thinking that the pump inlet filter was plugged with sludge. The filter turned out to be very clean, with little sludge in the bottom of the pan. The tube from the engine compartment to the oil gauge is clear as far as the elbow through the block. Not sure what else to check. Can any one offer suggestions that might help me solve this apparent problem?

Thanks.

fastfarmall · Feb 20, 2017

What viscosity of oil u using, 5W-20 or thicker, maybe your bearing's are wore,Have you ever used plastic gauge used ! Are they the original bearings ?

Doug Kieta · Feb 20, 2017

I use 30W oil. I don't know about the bearings as I bought the tractor used with no idea of the hours on the engine. I have never used plastigage.

rustred · Feb 20, 2017

i would say all the brgs. are worn. the thick oil will hold the pressure till it gets hot, then the pump cant keep up with the flow going past the increased brg. clearances. pull brg. caps on rods and check for visual wear , it will be seen .crank will be worn also. can use plastigage also. new crank and brgs. should be at .0015. but if your at .005 thats your problem. check mains also. and the cam brgs. will be worn also if the rest are.
if you want to run it as is use 20-50 wt , or straight 40wt. may help some when hot.

fastfarmall · Feb 20, 2017

Just a guess but i would say the bearings should be checked,they last a long time, but they could be the original's or maybe changed once. They can check it with plastic gauge!

riverbend · Feb 20, 2017

Plastigage is easy and fun. It is a plastic thread that you stick between the bearing and the journal. Torque the rod or main cap bolts. Unbolt the cap and compare the width of the squashed thread to the gauge on the wrapper. It is probably more fun to use when the motor is hanging upside down on an engine stand. Any auto parts store should stock it.

Greg

glennster · Feb 20, 2017

something else o check is the bottom cover on the oil pump. pull the cover, watch for the spring and plunger, then look for wear marks from the gears on the pump cover. if it has grooves wore in it, you can use a heavy piece of glass and some emery paper and sand the cover back level. or have a machinist make a pass on it. did that on my super m, and my farmall b. same problem, good oil pressure on start up, then once warm pressure starts dropping.

David G · Feb 20, 2017

10-20 PSI at idle is livable, is that at idle or at RPM?

Once you take it apart, you are going to spend money.

gene bender · Feb 20, 2017

I would try another guage 10lbs is enough

OldFarmall450 · Feb 20, 2017

I'm with Gene, I had low pressure at idle and I changed the original oil gauge on my 450, we also found a small leak on oil line under the dash. Now runs with higher pressure, idles hot around ten pounds.

rustred · Feb 21, 2017

yes, but 10 lbs may be enough to get by, but at idle that is where the wear is taking place on the brgs. the pressure should not change that much when idling. mine has 60 lbs. at 400 rpm.
anytime you have that much drop the engine is worn.
put your finger over a slow running garden hose you have some pressure and it sprays. take finger off and its a trickle. same principle with the worn oil pump and worn brgs.including cam brgs.

dhermesc · Feb 21, 2017

If its 10 psi at idle that actually sounds decent. If its 10 psi at pto speed then there is cause for concern.

rustyfarmall · Feb 21, 2017

(quoted from post at 15:50:00 02/20/17) something else o check is the bottom cover on the oil pump. pull the cover, watch for the spring and plunger, then look for wear marks from the gears on the pump cover. if it has grooves wore in it, you can use a heavy piece of glass and some emery paper and sand the cover back level. or have a machinist make a pass on it. did that on my super m, and my farmall b. same problem, good oil pressure on start up, then once warm pressure starts dropping.

Yes. My 1950 H had the same issues. Removed the bottom cover of the oil pump and found the 2 gears inside had worn themselves into the bottom cover. I milled down that cover until it was flat, and re-installed using a new gasket. Problem fixed.

KENIND · Feb 21, 2017

My 1940 H runs about the same oil pressure at idle. When she is higher rpms runs 30 - 40 lbs pressure. I figure that is pretty good for an old tractor that has bee used and abused its whole life 8)

OldFarmall450 · Feb 21, 2017

The IH operators manual for my 450 says oil pressure should be at the first mark at idle. That's 15 psi. Obviously these weren't high pressure engines, if a brand new off the showroom floor model is expected to have that low a psi. Mine has 10psi hot idle and 30-40 psi at WOT. The motor doesn't smoke, has no knocks, pings, no mains hammering at start up. Could the pressure be better, you bet. Am I going to invest a lot of time, effort, and money to fix a problem that isn't there, not today.

The Dukester · Feb 21, 2017

I was told by the local IH mechanic that the cause of low oil pressure at idle and engine warmed up was wear of the camshaft bearings and if you overhaul an H or M you should always replace them.

David G · Feb 22, 2017

It can be wear anywhere, cam bearings included.

H Oil Pressure Problem

Doug Kieta

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fastfarmall

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Doug Kieta

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rustred

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fastfarmall

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riverbend

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glennster

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David G

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gene bender

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OldFarmall450

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rustred

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dhermesc

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rustyfarmall

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KENIND

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OldFarmall450

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The Dukester

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David G

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