The Stovebolt Site Forums The Shop Area Engine Shop 1959 1/2 ton - 235 screwup...oil pressure issue

I think I screwed up. I changed oil in the '59 two weeks ago and it was black already from running the truck tuning it up, etc.

I drained the oil yesterday. Then I refilled with oil and added a quart of fuel oil and ran truck for about 20 minutes. I then drained it again and poured 2 quarts of fuel oil through it to flush the motor out. I refilled with new oil and installed new filter.

The truck always had great oil pressure but now the truck has great oil pressure at startup and then pressure starts to rise and fall like the pump is not picking up oil. If I shut it off, let it sit and restart there is great pressure again then rising, falling pressure.

My guess is there is sludge in the pan that didn't flush out and it is clogging the oil pump inlet after running a minute or so and then drops away when shut down, repeating each time the truck is started. ...OR.. the pump is pumping the pan dry and oil returns are partly plugged so oil takes too much time returning to the pan and pump starts cavitating.

Any ideas????

QUESTION...can the oilpan be dropped from the motor as it sits in the truck or do I have to unbolt and raise the motor. Truck is a '59 1/2 ton, motor is a 235.
thanks in advance...

Carl

Did you put 6 qts oil in ? If so sounds like you have either a bad gauge or a pick up problem. get another gauge and check that first, a lot easier than dropping the pan. If that doesn't work drop the pan,check the pickup tube, see if it's loose or broken. good luck.I pulled my engine, but I think there is enough room to get the pan off without that.

sounds like ya mighta cleaned too much sludge out and the pump can't keep up to the increased tolerances ... or ya didn't clean enough of the diesel out ... or ya knocked loose some chunks of sludge too big to get out the drain and they get sucked up against the pump intake .... so yeah, does sound like ya need to open'er up!

Bill

cjoe,

I don't know if your oil pressure gauge is mechanical or electric, but before I ripped into the motor, I would make sure the reading you are seeing is accurate, and steady. Could you pull the sender, or tube fitting, and let it purge and clean itself as you run the engine for a couple of seconds.

Attach a mechanical gauge and make sure the blood pressure is actually fluctuating...it's a simple step before major surgery.

Stuart

What pressures are you seeing? Does it fluctuate with rpm? I believe some drop in pressure is normal after oil is hot. Maybe bypass opening causing the drop?

Change the oil filter again and see if that helps.

Sure sounds like a blocked or partially blocked oil filter hence the fluctuating oil pressure when the pump starts building pressure.

What you would normally see is a low pressure when the engine rpm drops to idle and then a rise to normal pressure as the rpm increase but never a jumping around of the pressure at a steady rpm.

Before changing the gauge try cleaning the oil line to gauge provided your set up has that type oil gauge and I think it does.

To clean that line take it loose at the gauge and sending unit with compressed air blow through the line until it is clear.

If you have an electric sending unit remove it and clean the sensor end. In either gauge configuration as Stuart says "let it purge for a few seconds" before reinstalling everything.

Tommy nailed it with the question...did you put in 6 qts.? The answer...NO. It only took 4 1/2 qts.(with filter). I poured in a qt this am and lo and behold steady pressure about 45 lbs. The oil reads over full so I am thinking a PO installed the wrong dipstick. Anyone have a picture and dimensions of a correct dipstick for a '59 235?

No pic, but the dimension from the tip to where it seats on the tube is 15 1/2". Could be possible that the tube is too short, that would cause a faulty reading too. The tube should be about 7 1/2" from the block surface.

LONGBOX55.........I measured mine and it is 15 1/2" long overall... 1 1/4" from the end to the add line, and 5/8" from the add line to the full line. Is that what you get for all the dimensions??? I measured the tube and it is only 7"....
anyone else??

Carl

Mine measures about the same, it's 1 3/16" to the add line, but the other dimensions are the same as yours on the stick.

thanks Bill........that explains it,the difference in the tube length.....

Carl

cjoe, I'll check my old 235 stick and tube and get back to you, I have a 59 so it should be the same. My 261 holds 6 qts.

I had gotten a new dipstick and tube from a chevy dealer in N carolina, the part #1410541/MAYBE 91.THE DIMENSIONS 151/2 tip to top,17/8 tip to full,1 1/4 tip to add mark, and the tube looks to be 7 1/4 out of block, but it's dark in the garage so not sure. Hope this helps.The operators manual says 5qts, for the Thriftmaster,Jobmaster,taskmaster engines, 4qts for the trademaster, and 6qts for the loadmaster, and workmaster. The thriftmaster is a 235 and the Jobmaster is a 261. both 6cyl. the others are v8 engines.

your measurements are pretty much the same as longbox55 and mine. I think the issue is in the tube length and I'll bet it all depends on how far it gets inserted into the block....interesting though huh??? thanks Tommy

Carl

the way you tell it the screen is plugging after running a short time when you shut down some falls away and you have preasure agin...doc