C oil pressure

Russ from MN · Jul 13, 2009

We used our C quite a bit in the last week for mowing and I noticed when it's really warmed up it has very little oil pressure. The gauge is nearly impossible to see from the operators seat so they must of figured that it wasn't very important! The existing gauge doesn't have any numbers on it so I temporarily replaced it with a 0-30. At idle it had about 6psi and full throttle about 20, with new sae 30 wt oil, is this adequate, or should I make plans to do some repairs? what about just changing the rod bearings and leaving the mains, it runs really well, I hate to do a lot of unnecessary work on it, it's only going to cut some grass and go to an occasional parade! Thanks!

mattofvinings · Jul 13, 2009

Before you get into bearing clearance issues, I'd have the pan off and look at the oil pump's gear and end clearances and pressure-relief spring-ball. A lot of the characteristics of the oil system's performance are "setup" right there...and a lot less work than a full micrometer and plastigage teardown.

CLIFF S · Jul 13, 2009

Russ, The oil pump is the Problem! The pump Buttom that bolts on and has the pickup tube attached is Alumuium and gets warped over time! All thats needed is the Aluminum housing surfaced and a new gasket and your Oil Pressure will be Back Up to Normal!

Cliff S

Russ from MN · Jul 13, 2009

Thanks a lot! What is normal oil pressure?

Anonymous-0 · Jul 13, 2009

I have had my C for almost 30 years and the oil pressure gauge has behaved exactly as you describe the whole time I have owned it. I am glad to know what real numbers are.

Anyway, with no disrespect to the many VERY knowledgeable folks who correctly suggest the oil pump repair, you might just let it ride and make sure you get a little needle movement when you increase the rpm's when warm. I had occasion to have my valve cover and head off and everything looked like it had been getting plenty of lube using this management technique.

My advisor, who has 30+ years in at Cummins as an engineer says that in a low rpm engine like that any oil pressure is enough.

Owen Aaland · Jul 14, 2009

When the plate warps it also blows the gasket.

After getting the plate flat again, I make a steel reinforcing bar to span the area where the gasket blows out. Before installing I put a slight bow in it so that it applies pressure in the center. I have never had a repeat failure on any that I have done this to.

TractormanNC · Jul 14, 2009

Hey Russ,

Lots of good info here.

A good tight engine with 30 wt oil will hold 45-55 psi hot at WOT all day long. Oil pressure at idle should be at least 30 psi.

NDS · Jul 14, 2009

I have A that I have ran for over 40 years, 2 or 3 hundred hours/year for 25 years or so and maybe 20/30 hours year for last 15 years and it has never and any more oil pressure than your C when hot. The As, Bs and Cs are noted for having low oil pressure. I would run it with no concern.

NDS · Jul 14, 2009

You are right on some engines. I have owned at least 10/12 small block Chevrolet and GMC engines, several I bought new and none of them ran over 30 PSI at highway speeds when hot Have ran them up to 250,000 trouble free miles and have towed trailers coast to coast with them and if they will live with 30 PSI at 3000 RPM all day a C should get by with 20 PSI.

C oil pressure

Russ from MN

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mattofvinings

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CLIFF S

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Russ from MN

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Anonymous-0

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Owen Aaland

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TractormanNC

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NDS

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NDS

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