low oil pressure

[amaurer]

posted here instead of diesel tech because this is a general question.

I've always had less-than-stellar oil pressure, 36psi @ 3000 (which is exactly the spec limit for a 3B), but its never wavered so I was ok with it. On the very last day of a 10 day roadtrip (now completed), my oil pressure started to fluctuate, however...

The funny bit is, my oil pressure would come up just like it always did until 2500 rpm, when it would start to decrease a few psi to ~32psi or so. It did this like clockwork - I was nursing it home for 8 hours so I had time to "play" with the phenomenon.

I've done the following:

-Oil/filter was changed just prior to the trip.
-Main bearings are new, did that a few months ago just for s***s and giggles.
-Rod bearing clearances are fine.

After getting home:

-Relief/bypass valve is free and clear.
-Opened oil filter, no debris/material.
-Replaced oil filter, no real change.

I'm thinking either the spring for the relief valve is tired, or the pump is shot. Any of this sound about right for either of those? 3B oil pump is irritating to replace, its installed in the back of the timing cover.

[I should add that all of these readings are done with a mechanical gauge]

 

[dargreg]

Could also be the brand of oil and its viscosity

 

[Buckwheat]

Multi-viscosity?

I run 30W year round, but don't drive anywhere it's cold. Try running a straight weight oil & see if that makes a difference. How many miles on the engine? Is it running hot?

 

[Japan4X4]

Check the gauge calibration first. I spent many days trying to get a vacuum pump to work right. Turned out the gauge was off.

 

[Fuzzy Logic]

Seems your not alone-----------> YouTube - oil pressure gauge 3b diesel

 

[Degnol]

At least in a gasser, worn cam bearings can cause pressure to fall off at sustained higher rpms. But I don't know about diesels.
GL

Ed

 

[Michael Hanson]

These things always happen on trips! Im leaning toward the pump getting worn,but also check wiring. 2 cents Mike

 

[Buckwheat]

Please note:

The man said he took the readings with a MECHANICAL gauge! Speaking of cam bearings, could one have spun & blocked an oil feed?

 

[amaurer]

well, since you asked - I think I do have a bad cam bearing. a long time ago I found an alarming amount of metal in my oil pan:

IH8MUD Forums - View Single Post - oh no! metal in oil pan!

I very carefully measured the curvature of the pieces and found that they came from a bearing with an ID of somewhere between 48 and 55mm:

IH8MUD Forums - View Single Post - oh no! metal in oil pan!

At the time, I didn't know what this was from, as its too small to be a main or BEB, but I finally checked the EPC and find that 3B camshaft bearings are ~53mm ID... so it looks like at least one of my camshaft bearings is blown up.

Maybe I need a new thread, but its my understanding that this would be a tough or impossible job to replace in the truck for any of the bearings except the forward-most.... true?

 

[Degnol]

Well again, I dunno much about diesels, but replacing cam bearings requires a special tool. I think the same tool is used to press in the new ones. I had the machine shop install mine. So, if that holds true for diesels, it would be difficult, but not impossible to do with the engine in the truck.

Ed

 

[Buckwheat]

Pull it

Sounds to me like yer gonna have to go through it. On the 2F engine, all cam bearings are different sizes & the block has to be upside down so you can see what the hell yer doing. The installation tool can be had for about $150. Local machine shops charge about $30. You prolly have bearing material throughout the lube system by this time, too. I know that's what you wanna hear.

 

[amaurer]

Just to close the loop on this, yes, it was a cam bearing, but thankfully only the first one, so I was able to replace it in the truck. Pics.

https://forum.ih8mud.com/diesel-tec...-source-my-oil-pan-metal-3b-cam-r-r-pics.html