UB Special/UTS Special Oil Pressure

Curt Cooke · Apr 9, 2015

I have one and as I see it, the engine lubrication system is a by-pass system and that seems like a step backward to me. Were the U's, G's, etc. full flow or were they by-pass systems also? Never gave it much thought. On the Special, the only oil going through the filter is metered with a small orifice and once through the filter its simply dumped into the crankcase. Now what has me thinking about it is that I have a vacillating oil pressure gauge that various between little and then no, oil pressure. My guess is a plugged floato which I have cleaned, being thankful for the man-size whole in the oil pan that accepts the filter canister. Once I get a couple of gaskets and a new oil filter and put it back together, I'll report back on the outcome. Just seems that a by-pass system is a major step backwards.

brian(MN) · Apr 9, 2015

I have had no experience with UB specials, but some time ago a friend got a UB that had sat a while. He got it running and had no or little oil pressure, he found out some little tube or hole was plugged. Cleaned it out and he had pressure. Maybe that was that small orifice you mentioned.

rminont · Apr 9, 2015

I rebuilt a U special several years ago and had the same problem. I took the oil pressure regulator apart and gave it a good cleaning. That didn't seem to do any good and I ended up replacing the plunger. If that's what it is called.
The old one looked to be in perfect condition but the new one fixed the problem.

Paul in MN · Apr 10, 2015

Most truck, tractor, and car engines from that era have a bypass filter setup. It was an improvement over the prior "no-filter". The advantage of the bypass filter system is that the engine gets oiled no matter what condition the filter is in. If it is totally jammed with crud, the engine still gets oiled. The other major advantage is upon start-up we do not have a dry engine waiting for oil to fill the filter. The one thing we have to watch for as we work on these historical pieces is that we know the system absolutely needs the tiny orifice to limit the flow of oil through the filter or else we will have very low or no oil pressure, and that usually means we are starving the upper parts of the engine. The UB Special is an interesting system with the oil filter within a can inside of the oil pan. The PO of my UB Special never knew there was a filter there so it never got changed. Now the old memory begins to fade... is the flow limiting orifice built into the filter end plate gasket??

Paul in MN

Curt Cooke · Apr 10, 2015

The orifice is somewhat fixed to the oil pan. But I was reading my books last night and I think that I read in my UB book that the oil filter on that unit was a full flow type and that oil must get through the filter before it can get to any bearing. If that's true, it seems that the following model (the UB Special) is taking a step backwards by using a by-pass system. But I see your point, perhaps there's pros and cons to each system.

Cjet · Apr 10, 2015

Here is a pic of the restrictor orifice on my UTS Special.

Paul in MN · Apr 10, 2015

Thanks for the photo. The oil filter is currently closed up on my Special, so seeing your photo is quite helpful.

Paul in MN

UB Special/UTS Special Oil Pressure

Curt Cooke

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brian(MN)

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rminont

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Paul in MN

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Curt Cooke

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Cjet

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Paul in MN

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