Oil Pressure drop with AC
You lose a few rpm's when you turn the compressor on b/c it requires power to turn. When rpm's drop oil pressure will drop some b/c the two are directly related. Oil pump turns off the cam, so cam speed = rpm = oil pump speed.
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Chances are bearings are worn out, which isn't good. Is the oil fairly new? It wears/thins over time. For you next oil change I'd step up to a 10W-40 as long as it doesn't get below freezing (which it shouldn't this time of year) and see if that keeps your pressure out of the red.
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Okay. What oil you put in? Check the oil filter you have. Fram for example are restrictive in general and tend to lower oil pressures. Consider a KN filter instead. After the rebuilt, did it had good oil pressure? it changed after this first oil change? Did you change the oil pump when you rebuilt the engine? After a rebuilt the clearances are tighter. If your oil pump was on its way out these tighter clearances may have start to further push you oil pump downhill.
Thread Starter
On The Tree
Joined: Mar 2007
Posts: 141
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From: Colorado
I was thinking it was the pump. When I rebuilt the engine, the Oil pressure was fine, and the car hauled! Now, it seems even slower than my Jeep. Would the Oil Pressure problems have anything to do with this?
EDIT: Just found out, its not only with the AC on. ITs doing it with it off too. Driving speed and RPM, the Pressure is fine. But when I slow down or stop and the RPM gets to about 1,000 the oil pressure drops like a rock.
EDIT: Just found out, its not only with the AC on. ITs doing it with it off too. Driving speed and RPM, the Pressure is fine. But when I slow down or stop and the RPM gets to about 1,000 the oil pressure drops like a rock.
Last edited by Caveman1990; Jul 10, 2009 at 12:34 PM.
you should check your oil pressure with a mechanical oil pressure gauge make sure its not the switch my switch went out the oil pressure dropped to zero it was a brand new switch
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Joined: Jun 2009
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From: Tulsa, OK
The one and only way to know for sure is to get a mechanical gauge on it and see what it's really reading. Running rough, being slow etc. are side issues that don't have anything to do with low oil pressure (unless you really DO have dead bearings), so you need to eliminate the obvious first. When you say low RPM, what do you mean? If it's low enough, that will have an impact on oil pressure, but as an example in my S-10 at idle it drops to about 20psi idling. That's plenty for the conditions.
