Oil PSI dropped. Suggestions?
 

I posted this on CP and wanted to get as many heads together as possible on this one...

In November I changed the oil in my relatively stock and original 77,000 mile 1968 350. For the winter I used Rotella synthetic 5W-30 instead of my usual Rotella dino 15W-40. All was fine and I put the car away for a while.

Last week I took the car out for a ride for the first time in about 6 weeks. I started it up and let it warm up in the driveway. Then I loaded up the kids and drove away. A few minutes into the drive I noticed the oil PSI on my mechanical gauge was around 30psi on the highway. I'm normally running around 60-65 at 2600 RPM. (I have no idea but assume my OEM oil pump was changed before I bought the car.)

I pulled over and checked the oil level. Normal.
At idle the psi went down to 5! It's normally around 20PSI!

I stopped at a store, let it cool the checked the level again. Full. I added 1/2 qt just for good measure.


So, I pulled the synthetic oil out and put back on Rotella 15W-40 dino oil and a new filter. (I actually changed it twice today.)

After warming up the car to about 170*, I still get 35PSI at 2600 RPM and 5 lbs at idle. No lifter tick. Oil level is fine. nothing's leaking. I let it idle for about 5 minutes and it still sounded fine. runs fine.

When I wind out the motor, I get 60-65psi at 4,000 RPMs and over. It seems fine except that it's so different than how it used to behave.

What the heck happened? Should I be freaking out?

HELPPPPPPPPPPPPPP!

Maybe some bit of debris holding the oil pump bypass valve open slightly?? JAT

Check it with another mechanical gauge. Take out the sending unit or line and try another gauge. If it's still low it sounds like the oil filter adapter bypass might be stuck. I would say to take off the oil filter adapter and clean out the bypass. After that the check valve in the oil pump might be stuck. That's a little tougher.

so should I just pull the pan and get a new oil pump (mostly so I know what pump I have since I bought the car assembled)? If so, how do I pull the pan without pulling the motor?

But what I don't understand is why it just happened all of a sudden with the car NOT DRIVEN in weeks. I guess if I have debis, it'll happen any time. Just seems odd.

What about dumping in STP first and running it for 30 minutes or so on highway? Asking for trouble?

Check your pressure with another gauge that's known to be good as Jim Scites has suggested.

If your pressure is still bad, pull the engine and either fix the pressure relief passage blockage in your pump or replace the oil pump.

That pan's not coming off with the engine in the car, you'll have to get the engine halfway out just to get it high enough to get the pan off, so at that juncture removing the engine entirely is practically the same.

Much easier to work on the engine with it on a stand than with the whole car in your way while laying on your back.:gag:

Get it out and fix it before you damage it.

Best of luck.:cool:

I had luck one time freeing a stuck pressure regulator valve by starting the engine cold (the colder the better), letting it run for 20 or 30 seconds, and then speeding it way up (like 4000 RPMs) momentarily to get the oil pressure as high as possible. I had a mechanical gauge on it, and the instant the valve unstuck the pressure shot up. I had tried the same thing with the engine hot, with no success.

I don't usually like abusing cold engines, but I don't think it would hurt to try this a time or two. Don't think you have much to lose.

I use Amsoil 10-40 and my pressure has been like that for over 30,000 miles.
Idle 5-10
2000 rpm 35-40

I'd leave it alone and drive it.

I'd wouldn't be as worried about the 5psi at idle and 35 at 2600RPMs if this weren't very atypical of the engine. Concensus seems to be that I've got debris in the check valve in the pump. If I need to pull the pan, I'd want to replace the pan and I guess just replace the pump as long as I'm in there.

I really don't have the room to pull the motor. Can I unbolt motor mounts and other stuff and remove pan with motor in car? Oh man. It just sounds bad!

I'll try the cold start thing I guess unless I'm going to blow the motor (ruin bearings I guess).

If I've got 30 psi at speed, can I hurt the motor doing this a few times or is the PSI reading not the whole story if the valve is stuck open or partially open?

A while back mr.pbody (an engine builder) offered a tip. He said to replace the 5/8" inch check valve in the pump with a 9/16 ball from an industrial supply place. When doing it he said to shim the pump spring .060".

The difference in installed height is auctually .100 so that's what I'm shiming when doing this mod.

Here's a question: if I try to dislodge the debris by starting and running it cold, is there any chance in harming the engine during the process as long as I have decent oil pressure the entire time? I mean, right now at speed it's pushing 35psi. It is a true 35(as measured by my gauge - tube located at oil filter), isn't it? I mean, there's nothing weird that I'm not thinking about because of this relief valve being partially open, is there?

someone else suggested using a priming tool and drill to turn the pump with the filter area blocked off. The idea is to force ALL oil to flow through the relief valve. Then once dislodged, put the filter housing back on and remove the filter, then run primer again to flush debis into a drain pan.

Thoughts?

I opened the garage this morning to get the car colder. Just now I started it up and let it run for half a minute or so, then revved it to 4,000 RPM. Oil PSI went to 85 lbs. I brought the RPMs down to 2600 and I only had 45lbs PSI. I did this a few times and it didn't seem to help. I shut `er down.

I guess I'll go try the trick of using a primer tool and blocking off the oil filter adaptor. If this doesn't do it, I'll start crying. Oddly enough, the wife told me to stop messing around and just pull the motor! (she has no idea what she's in for!)

Listen to your :wife: and just git 'er done.

Today I tried an experient that someone from CP suggested. The basic idea is to block oil flow to filter and them spin pump with primer to force oil to flow through pressure regulator ball and spring in hopes of clearing out the debis caught in there.
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It goes like this:

I removed the oil fiter housing. It was pretty clean (the spring, valve and all) except that I did find a grey piece of rubber in there. (see pics) It's a broken off piece from something, not a piece of silicone. It's about 3/8" long but part of something that was round. I traced it out to be a complete circle which is about 1/2" diameter. it's light grey, and soft and rubbery. It appears to be a manufactured item as it's got circles or ridges along the outside of it. Similar to the O ring used on the water pump connection to the intake manifold, but softer and much thinner.

Anyway, on to my results. First I bolted the oil filter housing back on with a piece of aluminum sandwiched between it and the motor to close off the oil holes. Then I started the drill and priming tool. After just a few seconds, maybe 20 or 30, the RPMs of the drill seemed to pick up. I continued for about 2 minutes then stopped, thinking I may have freed the pressure regulator ball.

I then removed the aluminum block and reinstalled the filter housing, but not the filter. I again ran the drill and primer and watched a bunch of (BRAND NEW!) oil come out into a drain pain, hoping to flush out whatever was in the pump. I dumped about 2 qts.

Finally, I put the filter back on and had my 7 year old ;-) run the drill again while I watched the oil gauge. Yesterday, the drill was only able to produce 20 psi. This time it quickly went to 25psi!!! At this point I'm thinking it's fixed! (I was wrong)

So I put the distributor back in, topped off the oil, adding a bottle of STP for good luck.

I fired it up (got the distributor back in correctly on the first shot ;-) and the psi went right up to about 70 or more psi!!!

Unfortunately, that didn't last. As the car warmed up, it was dropping. And now, it's back to where it was before I started. About 30 at 2600. The pressure at idle eventually dropped back to 5, although it seemed to take longer to do that this time.

So, the only thing that encouraged me was the fact that my drill produced 25psi this time instead of 20psi. And that was before I put the STP in.

What do you all think? I'm thinking I'll repeat the process but run the drill for a lot longer with the filter bypass installed.

Other ideas?

What's the point of the smaller regulator ball?

Werd.:attention

Likely to help any crud get past the now smaller ball, so you are less likely to end up in the predicament you're currently in.

Do a seach for the wisdom of Mr. P-Body, you'll likely find the true answer.

Good luck.

well, i just spent 2 hours playing with the car. I'm down to about 1.5 hours to get it all set up to prime the engine with my home made filter block in place and put it back ready for starting. I used a stronger drill, but it's the same RPM so it didn't make much difference except maybe pushing more psi when oil was cold.

Bottom line, no change. the hotter the engine gets, the lower the idle psi.

I guess I'll buy an oil pump, shaft and pan too - what the heck. So once I have the parts and the time, I'll try and do the deed. :-(

I realized I never circled back here to post reslults of my oil pump replacement. I used a cherry picker to lift the engine up pretty high to get the pan off. I replaced the pump, which solved all my problems! :D

http://www.photoworks.com/members/sl...key=AdamIsAdam

I took a look at your pictures. You may have another problem as the bent clip in one picture is the retaining clip for one of the lifters and the chunk of metal next to it looks like it could be part of the top of a lifter. You might want to pull the intake and lifter cover and check.

Yea, those items were at the bottom of the oil pan. I'm assuming they were from prior damaged lifters. I did a cam on this motor last year and the lifters I took out were in great condition. And the pump that I just replaced was the same Melling 60psi unit that I put in. so clearly someone was in this motor before, despite the 76k on the clock when I got it.

In other words, those are remains of prior carnage.

I've since purchased and installed VERY heavy duty magnets that are now installed on the outside of my oil pan near the drain plug. I also bought one of those HD magnets for the oil filter. I figure if there's any more metal anywhere, I'd prefer to trap it there than inside my oil pump... AGAIN!

Yea, I had exactly the same problem like 10 years ago...My oil pressure went south during driving in front of my eyes, this was on a newly rebuilt 455..Needless to say I was freaking out. Any, way pulled the engine, everything looked great, no metal shavings or anything...Bought a new oil pump...but before I installed it I said what the he^& and I took the old pump apart. I found a piece of rubbery material stuck in the check ball, looked like a small piece of a rubber, anyway, I pulled it out and freed up the ball and have not had a problem since. I took the new pump back