Oil Pressure Gage

[76okievette]

I have a question, when I am driving my car "76" L-48, I get some fluctions in the oil pressure gage. I have a normal pressure of approximatly 40 pounds but the gage goes as high as 55 pounds, the funny part, and what I don't understand is that when I let off the gas, RPMs go down, the pressure seems to go up. This seems just backwards to me. I never see any low pressure either at high RPM or at low RPM, 30-35 pounds is about as low as it gets. I just can't seem to understand why the pressue would go up when I let off the gas. Should I be looking at the sending unit or the gage as the problem, if there is a problem. Comments?

GO SOONERS

 

[tom102]

Re: oil pressure

I had a simialar problem on my 76, I replaced the sending unit with one from Autozone Cost was about $14.00 and problem was resolved. I hope this helps

 

[76okievette]

Great, I will try that lot easier than messing with the gage. Thanks

Great looking car!!!

 

[vettepilot]

I have a question, when I am driving my car "76" L-48, I get some fluctions in the oil pressure gage. I have a normal pressure of approximatly 40 pounds but the gage goes as high as 55 pounds, the funny part, and what I don't understand is that when I let off the gas, RPMs go down, the pressure seems to go up. This seems just backwards to me. I never see any low pressure either at high RPM or at low RPM, 30-35 pounds is about as low as it gets. I just can't seem to understand why the pressue would go up when I let off the gas. Should I be looking at the sending unit or the gage as the problem, if there is a problem. Comments?

GO SOONERS

Has it always been this way to some extent or has it just started this trend? Also, if it has always been this way, has it become worse? In other words if previously it changed by oh say approx 5 PSI, but now it's changing by 5-10 PSI?
The thing I'm thinking of is the thrust bearing clearance. The thrust changes with the amount of (load on the engine). As the thrust bearing wears the oil clearances will become greater, and therefore when the crankshaft thrust changes the oil clearances change, thereby allowing more or less oil to escape past that bearing. The result is more of a fluctuation in oil pressure than you may have seen previously. Of couse it also could just be a faulty oil pressure sending unit like somebody else already stated.
I would find a direct reading gauge, hook it up and take it for a drive to see if you can duplicate the readings on the direct reading gauge. If you get the same results, the sending unit and instrument gauge is OK. Then you can begin to look elsewhere. Good Luck!!!


vettepilot

 

[Macgyver]

where is the sending unit located? I have a bad reading as well and I imagine I need a new one. Is it next to the distrib on the drivers side behind the intake? My haynes doesnt say.

 

[Red69]

Yes, just behind the intake and where you said.

 

[tom102]

Oil pressure Sending Unit

Mac
On my car (76) it is located on the oil filter housing and not on the manifold. Not sure about an 81 I would think it would be the same but it isnt hard to spot it.