lost oil pressure

[48 Dave PA]

I just bought this 46 P U today,. the seller only put 1800 miles on it in 12 years. I start off on the 50 mile trip home with 40 to 50 lbs of oil psi.

All is well for about 30 miles when the oil psi drops to 10 lbs. I stop, still have oil and a cool engine, the next 5 miles the oil psi varies 5 to 20 lbs.

I stop and buy a qt of oil, that brings the psi up to about 30 lbs.

I made it home with no damage I Hope.Any ideas, suggests please. Dave

[brian hood]

Are you sure your oil gauge is working? It might be worth a 20 just to check it before an expensive rebuild.

[grey beard]

Hi Dave,

Believe I'd start with a known quality gauge screwed into the oil galley on the side of the block. Best case scenario is an old or faulty dash gauge. Worse case is really low oil pressure at hot idle, in which case, the next step would be to drop the pan and look at the pickup screen. When I overhauled my own engine I still had decent pressusre, but the pickup screen was nearly blocked completely with dirt. Don't know how it worked as it was.

Good luck. Let us know what you find. Where in PA do you live?

[MBF]

Hi Dave-I'm w GB on this, if the guage shows the same type of pressure variation you may want to check the pressure relief valve and spring. Amazing what just a little bit of crud can do. Good luck. Mike

[Don Coatney]

I had a similar problem where my oil pressure dropped while driving. My problem was the pressure regulator had a burr on it and would not move. Removed the burr and my oil pressure returned to normal.

[48 Dave PA]

One more note,after the engine cooled the oil psi was back to 45.

I will take your advise and take the pan off.

I will let you guys know what I find,I work so slow in it will be weeks before I get Back. grey beard I am in Titusville. Thanks Dave

[JBNeal]

The '49 had a low oil psi reading after warmup when it was running before the tow truck debacle. Cold was 40psi, but after driving it for five minutes to the next stop sign, the pressure would hang at 10-20psi all day long.

I took a few minutes to pull the regulator valve from the '49 this evening, using a wood screw to wiggle it out of its bore. Sure enough, there were two burrs on the valve, with the semi-circle burr more than likely matching the bore of one of the internal oil passages.

Has anyone seen an oil pressure regulator valve do this? My guess is that with the small amount of rust present, the valve was stuck in its bore until I fired up the engine the first time back in '03. My flathead experience shows as I had not even pulled this valve out for inspection when I did my in-truck engine teardown in '02. I reckon when I fired it up, the pressure jarred the valve loose, but not before goobering up the valve surface.

Anyhow, I'm gonna try to clean the bore out with some emery cloth glued to a wooden dowel, then flush the bore with brake parts cleaner to get the residue out. Hopefully the bore intersecting passages aren't too messed up.

[Don Coatney]

Has anyone seen an oil pressure regulator valve do this?

Re-read post # 5 above.