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No Oil Pressure with normal operating tempature

2K views 2 replies 3 participants last post by  johnsongrass1 
#1 · (Edited)
On my 1979 Chevy Pickup with a stock 350, I have no oil pressure when the engine warms up to normal operating temperature. When the engine is first started up, the Pressure is at around 40- 50psi, this is at idle. Once the engine warms up, all oil pressure is gone, and the needle has a tendency to jump up and down between about 0-5psi. When I am driving the Truck, my oil pressure is running at about 20psi. There is about 150,000mi on this motor.

I got this truck for free and when I first got it, the oil was thick like tar, the spark plugs were all full of sludge. When I would change my oil, the fresh oil would be black. I have since flushed the motor with motor flush, and the oil now appears to look almost clean. I think that my oil pump may be clogged up, but I am not sure. Is there a sending unit that sends the oil pressure to the gauge that could also be gone.

Any help please would be appreciated. Thanks.

Sorry, I forgot to post some specs on my truck. I am also using 10w40 motor oil.

1979 Chevy Pickup K10 4x4
Stock 350ci w/ exception of
Holley double pumper 4bbl 650cfm
224,000mi on Truck w/ about
150,000mi on Engine
 
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#2 ·
After the oil gets hot it`s thinner, and keep in mind most oil pressure gauges are not accurate below 10 PSI and some as high as 15. With that many miles on the engine and not knowing it`s past oil changes, then it`s a good chance the bearings have a lot of wear on them, and there`s little you can do to help this any, you can move up to thicker oil, but this will only work temporarely, the best thing to do is tear it down and build it before it self distructs. your oil pump could be stopped up, but I`d think if it was, it would effect pressure full time, and not when the engine is hot as you discribe.
 
#3 ·
150,000 miles say's it probably needs a rebuild but you might try to crutch it by decreasing the clearances between the cover and the gears that drive the oil pump. That will bring up oil pressure but it won't do anything to worn out bearings.
 
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