More oil pressure woes

[stevenelle]

A week or so ago, I posted a concern I had on low oil pressure on a newly rebuilt 218. I exchanged the oil pump with one from another 218 engine and fired it up this afternoon. Lo and behold, the oil pressure shot off the gauge (way past 80). I thought this must be a problem with the gauge, until I noted a large pool of oil forming on the floor. Oil was coming out of all of the fittings from the block to the filter. Now I am even more perplexed. What might cause this excessive oil pressure. Thank you for any information, suggestions or advice. - steve

[Norm's Coupe]

Congratulations, sounds like you've joined the ranks of the P15/D24 guys with destroying oil pressure gages, including myself. Many times after rebuilding an engine the oil pressure relief valve becomes stuck, or it it is re installed wrong. Or, it could have become scored when installing or removing.

The relief valve is on the drivers side of the engine right next to the starter on the P15's. You'll see a plug in the side of the engine there. Pull that plug and and remove the spring inside of it. Behind the spring is a valve so then pull it out. You may need a small magnet to get it out with. If it's stuck in the engine like mine have someone start the engine while you watch the valve. You may need to give the engine a little gas to build up the RPM's to force the valve out. Mine was really stuck so really had to rev the engine to get it out. Once it came out, it shot out like a bullet so make sure you're not in it's way. Once out, clean if off and look for any scuff marks on the sides. If it has scuff marks buff them out with a buffer. If you can't get them out with a buffing wheel you could try emery cloth, then buff smooth again. That valve has to be smooth with no scuffs. If you can't get the scuffs out then it needs to be replaced. The procedure is in the P15 service manual so it should also be in the truck manual. When re installing you have to make sure the hole in the one end is facing a certain way (forgot which way off hand). Then put the spring and plug back in and start the engine again and the oil pressure should be back to normal. Also make sure the inside of the hole in the block is smooth before re installing. I would recommend hooking up an aftermarket gage under the hood to check it with before replacing the dash gage. Sometimes it is also necessary to replace the oil pressure relief spring when this happens.

I lost the needle on my dash gage too and like I said above several people with the P15's and D24's have too. It's a learning experience, but now your dash gage is toast and it will need to be replaced too.

[stevenelle]

Norm - Thanks for the good insight on the oil pressure problem. I tried today to let the oil pressure shoot the valve out with no success. Oil is under such high pressure, it is spewing out everywhere (filter connections). Just the day before with a different oil pump, I had very low pressure. I'll keep trying to get the darn valve out. At least now I know what the problem is. Anybody got other suggestions?

[Norm's Coupe]

If that valve is stuck that bad I would disconnect all the other lines for the oil filter etc. and plug them. That way the only possible opening would be the relief valve opening. As I mentioned mine was really stuck bad too. I was operating the throttle by the linkage under the hood. I think I was reving the engine so high it might have gone about 50 MPH and held it there for a minute or more before that valve shot out of there. Once out the oil did not squirt out, it just came out like water from a faucet. Had my wife sitting in the car so then told her to turn off the car real fast. I realize you can't see in that hole very well, but are you sure the valve is even in there. Maybe stick an awl or something in there to see if it's really there, but I guess it is, otherwise the oil would just flow out the hole. The valve itself is only about an inch long or slightly longer.

To give you some sort of idea on how bad mine was stuck. When it did shoot out, it hit something under the hood, bounced off it, went under the car and out the side, hit the garage floor and flew about 10 feet and hit the garage wall. That's why I said make sure your not in it's way when it comes out. It's like a bullet out of a gun.

Sorry, but that's the only way I know to get it out. Drilling it out would be hard because the valve is stainless