88 chevy 350 low oil pressure at idle when hot but is fine when above idle, or cold. I think it is the guage but am not sure, do not want to mess the engine up.

Get a mechanical gauge and hook it up to double check. You don't say how many miles but it sounds like the main bearings are wore out.

88 chevy 350 low oil pressure at idle when hot but is fine when above idle, or cold. I think it is the guage but am not sure, do not want to mess the engine up.

Low is not a real good description, how many PSI is much better. So, how many PSI at what RPM?

If I remeber right, the GM manual dictates that 4 psi at idle and 7psi at 2000 rpm is acceptable.........yeah right.......when you are used to 30 psi at idle, and 45 psi at speed, if it dropped down to that point, there would have to be some worn components.

Those centerbolt engines are very tough to oil starvation and low oil pressure, and that's from personal experience, lots of story's behind that, another thread for another day.

The sending units are known for failure after time, and that is probably the culprit. Yours is located above the oil filter on the left side of the block. The one behind the distributors on those years is just for powering up the fuel pump. On later years they went to one combined three wire sender behind the distributor.

If I remeber right, the GM manual dictates that 4 psi at idle and 7psi at 2000 rpm is acceptable.

I think the proper operating pressure is above 15 psi, the low side that trips the oil light is 7psi and below. I think your right that its the sender, the inside gets eatt'n up over time.

If I remeber right, the GM manual dictates that 4 psi at idle and 7psi at 2000 rpm is acceptable.........yeah right.......when you are used to 30 psi at idle, and 45 psi at speed, if it dropped down to that point, there would have to be some worn components.

The sending units are known for failure after time, and that is probably the culprit. Yours is located above the oil filter on the left side of the block. The one behind the distributors on those years is just for powering up the fuel pump. On later years they went to one combined three wire sender behind the distributor.


I think you might be on the money.. I have a 88 that did basicaly the same thing a few years back.. I was riding thru town and noticed the pressure had dropped down low enough to worry me.. I wasn't to far from my buddies shop so I pulled in and checked everthing out.. So we went and picked up a new sending unit and put it on.. But guess what the new one showed even less oil pressure.. Come to find out it was no good right out of the box.. We took it back and got a replacement and put it in and everthing has been fine for the last 5 or 6 years.. So just keep in mind that you might get a bad one even though it's new..

couple of my budies that race seem to agree 10 psi for every 1000 rpm

my 88 silverado with a 350 is the same way.....on really hot days when the temp is up at abot 190 the psi is about 18

How can you guys come to all of these conclusions? He hasn't even said how many psi there actually is yet :confused: .

What seems low to him, could actually be a normal opperating pressure.

88 chevy 350 low oil pressure at idle when hot but is fine when above idle, or cold. I think it is the guage but am not sure, do not want to mess the engine up.
Sorry about that, the oil pressure drops to 0 really fast at idle but if you touch the gas it shoots back up really fast. Any other time it is up to 30 or 40 psi. It is only when it is hot. I replaced the guage and hooked it up behind the intake manifold. It still reads the same thing.

Sorry about that, the oil pressure drops to 0 really fast at idle but if you touch the gas it shoots back up really fast. Any other time it is up to 30 or 40 psi. It is only when it is hot. I replaced the guage and hooked it up behind the intake manifold. It still reads the same thing.

Do you have the correct amount of oil in the pan? Are you using a mechanical or electric gauge? Have you checked the gauge you're using on a different vehicle to see if it's known good?

Do you have the correct amount of oil in the pan? Are you using a mechanical or electric gauge? Have you checked the gauge you're using on a different vehicle to see if it's known good?
The oil is good and the guage is mechanical, I havent checked it on another vehicle but it is brand new, Am I supposed to hook it up behind the distributor or at the sending unit.

fawk it just rebuild the motor :flipoff2: