High as a kite

[normanpitkin]

My 1948 New Yorker has oil pressure of about 75 when cold ,dipping to about 45 when hot.It used to be about 45 cold and maybe 15 hot and this has suddenly happened.So far i have changed the oil to 30W mineral ,changed the full flow filter ,removed and cleaned the pressure relief valve and checked its operation .I have also checked the pressure using a different gauge so i Know it isn't that! Now what?Am baffled!

[Don Coatney]

Is your oil pressure release spring broken?

 

[Don Coatney]

Also did you chuck up the pressure release plunger in a drill motor and polish it to remove all shellac?

 

[normanpitkin]

yes ,i did both those things! i am worried that there is a blockage and i  am not getting any oil to  the bearings ,also i suspect it will start to leak at these pressures!

[Don Coatney]

If you read the attached it shows that oil flows through the filter and into the oil galley for distribution. The oil pressure gauge reads the pressure in the oil galley and the oil galley supplies oil to the engine bearings. If your bearings were not being lubricated you would know it very quickly as the engine would seize. I suggest you re-examine the oil pressure plunger to insure it is moving freely and not bound up.

 

 

[VFFFrank]

I've been thinking about this for a while......At the risk of insulting your intelligence, the only device that controls the upper limit of oil pressure is the oil pressure regulator (duh!). At pressures below it's "crack point" (the point in the plunger travel that exposes the relief port) the regulator isn't in play at all. So.....the only thing that would cause the over-pressure condition you are experiencing is a failure of the regulator plunger to move far enough to open that passage, or the highly unlikely possibility of a restriction downstream of that passage. The baffling thing to me is that your hot idle pressure is also much higher than it was. At oil pump output volumes produced during idle, the regulator shouldn't be doing anything at all. Even if it was stuck in the fully closed position, the pressure should be as it always was since closed (or anything less than moving to the aforementioned "crack point") is the normal idle scenario anyway.

I realize that you have addressed that possibility already, but............

From what I read of my info, this is a C-51 or C-60?? I'm still getting familiarized with the Chrysler Corp. terminology.

Frank

[normanpitkin]

SUCCESS!!! i took out the relief valve AGAIN ,third time ,and at the suggestion of my brother in law ,cleaned it with ultrasound and then with switch cleaner .It was like a mirror by this point ,i then cleaned the bore in the same way ,reinstalled it and praise be ,pressure is now 45 cold and down to 25 after a 30 minute drive .Many thanks as ever to the invaluable assistance of the forum members!

[Plymouthy Adams]

I am not in any manner a friend of snake oil but I do recommend a bit of Rislone in high mileage engines be they modern or older variety..modern type this stuff will ensure you never have a lifter issue...in older cars, this product does clean and prevent varnish build up and such that can cause tight fitting parts to bind and stick..(similar to lifter inter-fit is your plunger).  If your engine has been on a diet of non detergent oil...any detergent additive will require frequent filter changes as the sludge and other contaminants are cleansed from your engine...as with all additives..follow directions and use some common sense.

[TodFitch]

. . .The baffling thing to me is that your hot idle pressure is also much higher than it was. . .

 

On these engines the oil pressure relief plunger also controls the return flow from the bypass oil filter. If the plunger is stuck in the low pressure position then it will be blocking the return from the filter which could raise your idle pressure.

 

Looks like the problem was fixed by cleaning up the plunger and the bore that it runs in.

[VFFFrank]

Yes I saw that! Glad to hear that it got fixed.

I'm aware that the portion of the plunger with reduced diameter is to allow flow from the bypass filter but this one has a factory full-flow, which appears to have the regulator in the pump cover and a filter bypass valve situated in the base casting of the filter assembly. Correct me if I'm wrong on this one....please. (You'd think as much as I hate being wrong, I stop it)

A filter bypass is NOT to be confused with a bypass filter. It's there to allow flow in the event of an excessively restricted filter element. A "bypass filter" doesn't need that feature.

The staggered port scheme disallows flow from the bypass filter at pressures below ~15 psi so as to not sacrifice any volume at low speeds.
You can imagine my frustration when I once wrote an article entitled "In Defense of the Bypass Filter" and our newsletter editor changed it to "......Filter Bypass". !!! It made my piece make no sense at all.

Frank

[Don Coatney]

Yes I saw that! Glad to hear that it got fixed.

I'm aware that the portion of the plunger with reduced diameter is to allow flow from the bypass filter but this one has a factory full-flow, which appears to have the regulator in the pump cover and a filter bypass valve situated in the base casting of the filter assembly. Correct me if I'm wrong on this one....please. (You'd think as much as I hate being wrong, I stop it)

A filter bypass is NOT to be confused with a bypass filter. It's there to allow flow in the event of an excessively restricted filter element. A "bypass filter" doesn't need that feature.

The staggered port scheme disallows flow from the bypass filter at pressures below ~15 psi so as to not sacrifice any volume at low speeds.

You can imagine my frustration when I once wrote an article entitled "In Defense of the Bypass Filter" and our newsletter editor changed it to "......Filter Bypass". !!! It made my piece make no sense at all.

Frank

There is no regulator in the pump cover on a factory full flow system. There is a spring loaded filter bypass in the full flow canister allowing the engine to get oil if the filter medium is plugged.

 

 

 

 

[Captain Neon]

Don, I appreciate this information about how oil filters work.  There was a self-proclaimed expert on another forum claiming that full-flow filters were dangerous as they would seize an engine if they ever got clogged.  He had no idea about bypass valves in full-flow filters.  He was also claiming that popular consensus was that our engines have to run on non-detergent single viscosity oil.  I asked him for his sources. He would only claim a plethora of articles he had read, but was unable or willing to provide a link to a single one.  After sharing your period drawings that demonstrate simply, but effectively, how both full-flow and bypass filters work, I asked him if he got his information about oil from the same place he got his obviously incorrect information about filters.  He didn't have a leg to stand on, and I haven't seen him spouting about non-detergent single viscosity oil since.

[casper50]

I love it when a "know it all" is proved wrong.  Good job

[VFFFrank]

OK, I see my error.....I think.

I saw that the P25, D44 & D48, listed as "with Hy-Drive" has a regulator on the pump cover. The Full flow system appears to have the regulator in the base of the filter unit as well as the filter bypass device.

F