Low oil pressure

[aero3113]

Hey Guys, I went for a 60 mile round trip today in the 50. Started off the trip with great oil pressure just above 40psi. Towards the end of the first 30 miles I noticed the oil pressure dropped near 0. It is normal for my oil pressure to drop when warm but it never went this low. I stopped at a light and noticed a different sound coming from my engine, when I accelerated it went away when the pressure went up. I made it to my destination and shut down. I checked my oil and it was at the add line. I put a quart in and let the car sit for a few hours. When it was time to go home I started up the car and had great oil pressure again. Again near the end of my 30 miles home I had the same issue.I noticed when I would accelerate the pressure would go up but it would go back down after I let up a little(at 50-55 MPH). I Made it home and put her in the garage. First thing that came to mind was the oil pressure relief valve. I pulled it out and I found a strange bump on the top of it (you can see it in the pics below) I can catch my nail on it. Do you think it was binding and causing the low oil pressure. Where can I get a new plunger and spring?

[PatrickG]

not sure about the replacement relief valve. but i'm not sure that would cause the disappearing oil

[Don Coatney]

Same thing happened to me a few years back. Chuck the plunger up in a drill motor and polish it with emery paper. Re-install and you should be good to go.

[Joe Flanagan]

Aero, my valve was frozen in its bore after sitting for seven years after a rebuild. When I tried to get my pressure up, it would go to 30 and no higher. I removed the valve, cleaned it (and the bore) with fine sandpaper, lubed it, and reinstalled. Everything was good after that.

[55 Fargo]

Hey Aero, hope this is a simple fix, let us know what happens with this today......Fred

[aero3113]

not sure about the replacement relief valve. but i'm not sure that would cause the disappearing oil

I think the oil was low because I did not check it in a while.

[aero3113]

Same thing happened to me a few years back. Chuck the plunger up in a drill motor and polish it with emery paper. Re-install and you should be good to go.

Don, what do you think caused the bump on the plunger? If I clean it up will I have any problems if it gets too small? I am not going to have time today to play with it but I will keep you guys updated. If you have any new ideas let me know.

[pflaming]

Where is this valve? My pressure is at 40 psi so I'm not worried, yet would like to know.

[1940plymouth]

At the lower, middle of the block just above the oil pan on the driver's side of the car. Rather simple to get at

[55 Fargo]

I think the oil was low because I did not check it in a while.

Nope, these old girls need there engine oil checked often, I check mine just about every drive. That my be a bit radical, but weekly checks should be the order.

At 2 quarts low your oil pressure will bob up and down.........Fred

[Don Coatney]

Don, what do you think caused the bump on the plunger? If I clean it up will I have any problems if it gets too small? .

Bump, I think, is a build up of combustion (dirt) by-products.

Clean it and try it. If you find your oil pressure out of range after a couple minutes of running then additional action may be required. But I believe this will fix your issues.

[aero3113]

Bump, I think, is a build up of combustion (dirt) by-products.

Clean it and try it. If you find your oil pressure out of range after a couple minutes of running then additional action may be required. But I believe this will fix your issues.

Its not build up,its like a high spot in the metal. You can see it in the pics (top ring)