Low oil Pressure

Tiny
RON1201
  • MEMBER
  • CHEVROLET S-10
I have a pickup with a 2.2L. With low oil pressure. When cold it runs sixty psi, but when warm it drops down to about twelve. Just put in a re-manufactured crankshaft, bearings, rods and mains, also put in a new oil pump and pickup. Any ideas why this oil pressure drops? Used a mechanical gauge, so the sending unit seems to be working right.
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Wednesday, November 28th, 2007 AT 10:15 PM

3 Replies

Tiny
PEAR69
  • MEMBER
I love oil pressure questions. Oil pressure is not made by your pump. Oil pressure is made from the restrictions or resistance in the oiling system, like, thick oil, oil gallery, bearing clearances, bends in the oil lines, dirt clogging oil lines, etc. Etc. An engine needs ten psi per 1000 rpm. What is the rpm of the engine at idle? Always remember high oil pressure means that there is more resistance in the system, and a bigger volume pump creates a larger volume of oil flow thus creating more resistance and a higher pressure. A high pressure is probably worse than a low oil pressure. Was the pump primed properly?
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Wednesday, November 28th, 2007 AT 11:40 PM
Tiny
RON1201
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Yes the pump was primed. Would it make a difference if we went with thicker oil? Currently there is 5/30 in it.
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Thursday, November 29th, 2007 AT 5:01 PM
Tiny
PEAR69
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If your engine is designed for 5w30 oil then no. It usually tells you the weight requirements of the oil right on the dip stick of the oil filler cap.
If the rpm's are 1200 at idle, then twelve psi of oil is perfect! Even ten is okay at this rpm. Remember ten psi of oil pressure for every 1000 rpm's. Putting in a heavier than designed weight oil will be disastrous! Yes your oil pressure will go up however this is because there is more resistance in the system, bad. A heavier weight oil puts a lot more strain on the oil pump. It also takes more horsepower away from the engine because the oil pump must work harder to push the heavier "resistance" throughout the system. Do not believe me? Well, when a Nascar race car goes out for qualifying it usually has in it a 0w15 or (if they can get it) 0w10 weight oil. They run a scary low viscosity oil when qualifying in order to get the most horsepower. Your problem if you want to call it a problem "which I do not" may be that the bearings have too much clearance, unequal clearance, oil passages are a little clogged up or your oil pressure regulator spring is weak. High pressure is, as bad, and worse than low pressure!
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Thursday, November 29th, 2007 AT 9:58 PM

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