The Stovebolt Site Forums The Shop Area Engine Shop no oil pressure

Hi Guys. I'm back for some more advise. Yesterday i took out my 55.1st series for her second run. This time we went a few miles. I stopped and let it idle while talking to someone and after a few minutes I heard a lifter start to clack. When I started home I noticed very low oil pressure. As I drove it home the clack went away as the oil moved back up with the higher engine rpm's. This engine does not smoke not even a hint and the lower end does not rattle. How would I diagnoes whether it's the pump or the motor and are there any inherent things you guy know about the later 235's. Is there a screen on the pickup that needs to be cleaned or any info will help.

Thanks
Tony

Crud & grit in the oil pan can cause this. When it sets the foriegn material falls into the pan. After you run awhile it is picked up by the pump & clogs the screen. You should pull the pan & clean it out & clean the screen.

Thanks , I thought that may be the case but wanted to hear it from someone who knows. The next question is can the pan be pulled on these trucks without raising the motor?

Another thing it COULD be is loosening tolerances in the main and connecting rod bearings. If the pick up screen looks to be clear, then I would start making plans for a rebuild.

The reason I'm suspicious is because I don't know why there would be a bunch of foreign material and crud in the oil pan...unless you never change the oil.

The pan can be pulled without raising the engine.

drive it a 1,000 miles and the clack will go away ..

Ya I am afraid it may need a rebuild but I will try the oil pump first . The thing that gives me hope is that the motor does not smoke and the bottom end sounds tight. I wonder if oil pumps kind of wear out and if it would not hurt to try and replace the pump.

Thanks
Tony

wonder if it would help to put some stp or something like that in it........I dont know a lot about these old trucks but my oil pressure sometimes will go down and come back up,,more so if Iam stopped,, on the move it seems to be constant.....dont know if I would change the oil pump unless Iwas pretty sure that was the problem.. how long have you had the 235, how many miles have you put on it?

I've only had it a couple of months and it was in pieces when I got it so I just got it on the road and have only driven 5 miles max.

What weight oil are you running? If you are running a multi grade, try switching to straight 30 weight. If that does nothing or very little to help the oil pressure, I would look elswhere, like Hot Rod Dad says about the rod and main bearing clearances. If just one is shot, that can make the oil pressure drop.

You could drop the oil pan and check the main and rod bearings, oil pump and clean out the sludge on the bottom.

I might catch some flack for this, and I wouldn't try it on a good running motor, but you could empty the oil, and fill it up with deisel fuel. Pull the spark plugs and with the ignition off, turn the motor over and try to "wash" the inside of the engine. To save the starter, you could even pull the truck around the yard in gear to turn it over. This might disolve some of the junk that may be clogging your screen. You might want to drain it and do it a second time while you are at it. When you have done that, drain the diesel fuel and leave the engine sit with the drain plug out to make sure it drains well. Then fill it with your new oil, and spin the motor again to get the oil lubed before you start it.

I said I might get some flack about it because if non detergent oil has been used, there may be a lot of buildup inside the motor and you may be loosening a lot of that stuff. Using diesel fuel will most likely disolve some of that stuff before breaking chunks off, but it sounds like you probably may be working internally in the end any way.

Keep us informed.

OK, well I pulled the pan and it looks like a new motor. The oil was new and it looked good a little brown just from washing back the old oil but no slug at all. The bottom of the pan had just a very little build up in it. There is a baffle in the pan that someone has knocked flat. I dont know exactly what it was there for but I wanted to mention it. I cant see into the pickup screen and want to remove the pump so I can get into the screen and make sure its clear and maybe even change the pump if that might help. I removed the four screws that seem to be holding the pump on but it would not drop out and I did not want to get the biggest hammer before I asked if there is a trick to it from you guys. Oh Ya, this engine has some sort of oil filter adapter on the left side of the motor it looks very simular in the installation to the old canister type filter I see on many of these motors but if has a spin on filter. Just wanted to add that to the info chain.

Thanks
Tony

Tony,

Just a guess, but to pull the oil pump I think you should pull the distributor, disconnect the discharge pipe, and then loosen a lock-nut jack screw setup that holds the pump in the block.

I think the four bolts allow only the pump cover to be removed....after you remove the discharge plumbing.


Stuart

Stuart, Thanks for the reply. I have never seen one of these pumps pulled out and it sounds like it should come out in one unit instead of pieces the way I was attempting to do it. So let me get this straight. If I pull the distributor out and look down the shaft that it fits in there will be a lock nut that is holding the oil pump up to the block and if I take the lock nut loose I will be able to remove the pump from the bottom. I have allready loosened the discharge pipe but did not want to force it as the pump would not move. Thanks in advance for the advise

Tony

Tony,

The little lock-nut jack-screw that I speak of is INSIDE the engine, up near the oil pump shaft.

It locks the pump housing into the block. You are merely removing the distributor so when you reinstall the pump, you won't hang up on the tang of the distributor shaft.

I have enclosed a link to a picture. I hope this is what your setup looks like, or I might be all wet.

You can see the screw and locknut in the picture.

http://chevy.tocmp.com/1929_54chevyparts/01/133.HTM

Stuart

OK, Now I understand. Its dark out there now but I will get at it tomorrow after work. The pump in the picture looks a little different but I can see how it is held in place. Thanks for stopping me before I opened up a big can of worms busting that pump apart while lying on my back under the car I would have had parts all over the place and not known where they went.

Tony

Tony,

I am not sure WHY you want to remove the oil pump. These things run in oil and don't usually give too many problems.

Good luck.

Stuart

Well I dont really know why I want to get it out either but I am trying to do everything I can to pull this motor out of the dumper. I dont have the money to have it rebuilt just yet and I am hoping I will see something that I can correct. I know they make high volume oil pumps and I though I might look into that. This may all be for nothing but I want to try everything before I give up. The reason I started pulling to pump is that I cant see in the screen and if I get it out into the sun I may find the obstruction.

The oil pressure at higher rpm while driving is what matters.
The manual for the late 235 calls for 35 lbs. of pressure at 2000 rpm.
On a used motor you could have a little less and you may see almost zero oil pressure at idle after it's fully warmed up and especially after driving on the freeway for a while.
No need for rebuilt if it doesn't burn oil and you have good and even compression on all cylinders.
It can go for a decade or more that way daily ... speaking from personal experience.

Oil pumps hardly ever need replacement or repairs. If its all clean without build up down there I wouldn't be worried about the pump.
There is a relieve valve piston and spring that could be stuck in the open position, but that is also pretty rare with a clean engine.

If you remove the valve cover when hot and the rockers get enough oil and the pushrods are spinning, you are good.
Do you have hydraulic lifters or solids?
Valve lash should be adjusted when the engine is fully warmed up.

Tony,

I will offer my unsolicited opinion. I read your first post on this subject. The oil pump is the absolute last component to wear out...it runs in oil its entire life.

You said a lifter started to 'clack'. I guess the rig you were driving has hydraulic lifters?

If the engine doesn't smoke, and runs relatively well, it certainly isn't in the 'dumper'.

If you are really concerned, you need to stick a test oil pressure gauge on it and confirm what the readings are.

These rigs can run with barely any pressure, and lifters sometimes do make noise.

I think you might be worried about something that isn't critical right now. If it runs alright, you might consider a heavier weight motor oil.

Does this engine have hydraulic lifters? They would be suspect before the oil pump. Dump a quart of ATF in with the next oil change and give them a little cleaning.

Stop for a moment and figure out what it is you are trying to accomplish. Its an old truck...all of it!

Stuart

Good point atomarc.

Gentlemen, Thank you for all the good advise on this problem of mine. It seems as though I may have jumped the gun on this one. I have heard more than once here that this may be normal and I should leave it alone, so with that said. I think I will clean the screen on the pump,button up the oil pan put in some 40weight oil and run it for a while. As far as the lifters go they are solids. I will run it with the valve cover off and make sure they are getting oil. If you have any other suggestions all will be appreciated. I will let you guys know how it goes and try to send some pictures to the gallery.

Thanks again
Tony

We have all been there at some point before these engines taught us lessons.
Amazing how long they last if you just keep up on maintenance.
Truly a 'don't fix it if it ain't broke'...

One more thing, since you are at the oil pump.
Use a high heat thread locker/sealer like Loctite for the screen pickup tube that goes into the housing - we don't want any air in the oil lines!

Definetly check for even compression on the cylinders.
They can run as low as 95 lbs. for ages if you don't push it.