The Stovebolt Site Forums The Shop Area Engine Shop Oil pressure problem 235 6cyl.

Hello, got a low oil pressure problem on an older motor, I belive this is a 1960 model 235 truck motor in my 51 chevy deluxe 2dr. Pressure seems to come and go and the vavle train will start to clack/knock when it does. If I shut it off and it will come back. I have the external canister oil filter if that makes any difference. Ive been told to swap the oil pump, but I took the pan off and the screen looks clean, nothing visable that would indicate a clogged oil pump. (also cant figure out how to get that puppy out of the block either) So any help would be appriciated. Thanks guys

Hy gearhead695456, this may seem a silly question, but are you sure your oil level is correct? Your oil level may be low and when the pump can no longer reach the oil, your pressure drops. When you shut the engine off and restart oil has returned to the pan. Try adding a quart or two of oil to the pan and see if the problem remains, try the simple stuff first, hope that helps.

Thanks 3B, that has been the case before, but this time it happend with full oil (overfill actually). The problem started after an oil change, when appearently I didnt get the gasket around the canister oil filter on right (duh) and it shot oil out at pressure while I was test driving it. So I stopped fixed the gasket and added the 3 quarts it needed at this point and continued to drive on. About 20-25 miles later im having this on and off again oil pressure problem.

Here is a link to the Shop Manual for the oil pump removal and service. This is for the 1955 2nd truck, but I believe that the oil pump on yours is similar. If you decide to remove the pump, do not attempt to remove the two large rivets that attach the oil pump mounting fitting to the block. Just remove the large set screw.

If there is too much oil in the pan there could be a problem as the oil could be thrashed around by the crankshaft and become aereated and not pump very well. I would remove or drain any excess oil; better yet, drain it all and add the correct amount of fresh oil.

It is hard to believe that the pump would suddenly go bad, but it is possible.

Good luck.

Hoyt

"So I stopped fixed the gasket and added the 3 quarts it needed at this point and continued to drive on. About 20-25 miles later im having this on and off again oil pressure problem."

After you added the 3 qts you continued to drive on? Did you recheck you oil level after driving? Many oil filter canisters hold oil in them. If your canister was empty before you added oil, you oil level could be low after driving. (just a guess: worth asking)

Hoyt, thanks for the shop manual was very explicative and the detail was good on the photos. This one differs slightly from my pump because it doesnt have the floating feature on the pick-up tube. I cant quite determind if the pin slides out and that is what frees the oil pump from the block? I understand not to remove the two rivets from the block that hold the outer housing, but instead just slide the pin out and the pump should drop out? tclederman, im starting to think that was the problem that the canister was not full and therefore sucking air....

This is what the manual says "Remove oil pump retaining sleave lock screw" where is this lock screw? cant see it on the engine, thanks.

There is ONE set screw that holds the oil pump in place, near the top of the pump shaft. The set screw has a lock nut on it. Loosen the lock nut first, then you can loosen the set screw and remove the pump. I have a '59 235 and I had the same problem you have. Oil pressure came and went. After checking and eliminating all of the easy possibilities, I finally replaced the oil pump. Now it's good as new, with steady, high pressure. The old pump showed no evidence of wear and tear, so the fix is a mystery to me.

thanks norcal, so this lock nut is on the inside of the engine block or is it visable from the outside of the block? Im doing this while the engine is installed in the car. Trying to get it ready for Billetproof this Saturday, crossing my fingers this will fix it!

Hy gearhead695456, the locknut and bolt are inside of the oil pan and not visible from the outside, hope that helps.

I GOT IT! Finally got the old one out and the new one is in there. I think I found my oil pressure culprit, when I removed the screen there was an entire pan gasket end piece stuck inside all dried and cracked up. This could explain the off again on again oil pressure. Looks like its from some genious' previous oil pan removal cause all of them were still on the pan where they were supposed to be. Now my question is should I prime the pump before starting the car? Well thanks guys for all the support.

Good job! Yes, you should prime the pump. I took an old, flat blade screwdriver (a long one) and cut off the handle. I inserted the cut end into a 3/8-inch drill, and the blade end into the distributor port to engage the oil pump. Make sure the drill is turning the same direction as the distributor. When the pump begins to prime, you will feel the load on the drill and see oil at the rockers if the valve cover is off.