oil pressure

[wv birdman]

I have a problem that i hope is not a problem.When i first start my bird the oil pressure gage goes up to about half way but when the engine gets warm the gage goes below low.I put a new sending unit on but it didn't seem to change things.Even while ideling the engine sounds great no pinging or other noises.By the way car has 100 thousand miles on it if that makes a difference.Can anyone offer some advice as to what may be the problem? As far as i can tell the gage is working just fine.thanks

[Joe Vandatta]

Did this come on over a period of time or all of a sudden? Since you have changed the sender unit I suspect worn bearings.It all boils down to changing oil and filter at recommended intervals.
Joe

[tbird5866]

I would suggest that you determine what your normal oil pressure in pounds per square inch. As opposed to high or low. Remove the oil pressure sending unit and install a mechanical oil pressure gauge. Your electrical set-up could be giving you false information.

[64RREDCONV]

My car does exactly the same thing. Please advise if you find the source of the condition.

[boaterbob]

I've had a couple 390'S with that problem turned out even with putting Rods and Mains in the problem was still there. They lose the pressure because of bad cam Bearings. First check is the guage of course.

[Joe Van Datta]

You know, one of the reasons they quit puting oil pressure gauges in cars is that a fellow could have the same vehicle as the guy next door and he does'nt carry the same oil press. There are many factors involved here but it usually boils down to excessive bearing clrearance somewhere. If you get a true reading with a mechanical gauge and it's very low you have a problem that is not easy to fix.
Joe

[64RREDCONV]

Originally Posted by boaterbob

I've had a couple 390'S with that problem turned out even with putting Rods and Mains in the problem was still there. They lose the pressure because of bad cam Bearings. First check is the guage of course.

Thanks for the input. If it is the bearings, why is the pressure initially high, with it going down only after the engine warms up? I do not doubt that could be the problem.

[Joe Van Datta]

When you start a cold engine the oil is cold and more viscos (thicker) even with the multiweight oils. This compenstats somewhat for the exsessive bearing clearance. When the engine gets to running temp. the oil thins out and pressure goes down.
Joe

[64RREDCONV]

Thanks Joe.

[tbird5866]

Originally Posted by 64RREDCONV

Thanks Joe.

Which is to say you may improve your oil presure reading with heavier oil.
An oil trick when selling a used car!

[64RREDCONV]

One more question: I did not mention that the pressure goes up when the car is being driven. It only drops at idle, such as at a stoplight. Still the bearings?
Thanks

[Joe Van Datta]

If you maintain oil press. at speed you are okay. Pressure at hot idle will always be low so I would'nt worry unless you hear any clatter.
Joe

[boaterbob]

You should check out your pressure like Fordman said if your worried. Be sure you have the correct sender I've seen people put a Idiot light switch where the sender belongs.

[65tbirdconv]

My car has a bad oil pump and has been run, not driven with this condition. Since I have owned it I have ran it at 3 to 5 mintues clips, idle in cold weather. How much damage have I caused? Is it worth having the pump fixed if I have killed bearings and the like?

[tbird5866]

How do you know it's a "bad" oil pump? What is "bad" about it? IF it were my car, I'd drop the oil pan, check the bearing clearances and replace the oil pump.
That won't cost a lot, but it would buy a lot of "peace of mind".. (Not necessary to pull the engine to do this.)