Low Oil Pressure when warmed up
 

I have a nagging issue which is when my engine reaches normal temp, 180-190degrees, the oil pressure drops to about 8-10lbs. When cold it is around 40lbs. I have replaced the oil pres guage so that's not it. I have tried dif weights of oil, now using HD40. I have tried diff oil filters. I have an oil cooler on the car but can't use it cause I'll get 0 oil pressure???!!(when cold).- the oil pres will raise when reving the motor so I think the oil pump is working. Its also brand new.- Brief history on motor; 86 block, stock lower end, ie all bearings etc. Not sure on number of miles. Cam bearings looked used but not shot so those where retained. 85 rebuilt heads fm a carbed mustang.---I don't remember if the oil pump pickup uses a gasket between the pump and the filter? And I don't rem if I put one there. I think it should use one.
What do you guys think? Thanks for any thoughts.-one other thing. Even w/the low oil pressure, oil still gets to the top cause I checked it while running....


[This message has been edited by ALS85GT (edited 10-17-2001).]

Do you still run the same stock electical gauge? Did you replace the sending unit?



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'91 LX convertible , T-5,Centerforce Dual Friction, FMS adjustable cable w/quadrant, ported/polished/milled E7 heads, 1.6rr, 1.94/1.60 stainless valves, BBK 1 5/8" equal length shorties, 2 1/2" off road H-pipe, Summit 2 1/2" catback, March Performance Pulleys and A/C Eliminator

I have exactly the same problem with my engine in the fastback. Even tried the same methods you mentioned. Nothing seems to help. I decided to leave it like that since the engine doesn't knock even on cold start ups.

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67' Fastback-Mean Temper
67' Coupe Under Construction
70' Torino Cruiser
84' Svo Original

I use AutoMeter guages. And I'm getting diff responces. Some says it's a pump issue(even though the pump is new), some say it's no big deal as long as you have about 8-10psi at 1000rpm(which it does when at 1000rpm).
The thing is that the engine runs fine, no noise what so ever, and the psi increases as the rpm increases. So this seems fine also. The engine is not new so I'm sure the old bearings have something to do with it.!??!I just want to be sure is all. Thanks...

It sounds like routine wear and tear to me. You are right about your engines requirements: 10psi per 1k rpm minimum. As long as you don't fall below that, you'll be fine.

~C

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Retired Moderator
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OK, thanks for the responces. I'm not going to worry about it(too much). But what do you guys thing about the oil cooler? I made sure the oil reaches the "In" port on the adaptor. It's a Summit Oil/Trans cooler. I get 0 oil pressure when using this.
thanks again...

If the engine is older than it's probably the bearings. My engine oil pressure drops after it warms up down to about 25psi from 60 and I only have 300 miles on my engine. But my thrust bearings need to be replaced due to a tranny overheat and is the main cause for my pressure drop.

your oil pressure should drop when its warmed up, compared to cold. This is normal. remember, pressure is resistance to flow. warm oil flows better than cold oil, less resistance, less pressure..

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1993 GT/AOD
'93 Mustang GT

Mine drops to 15-25 at idle when warm from 50 - 75 while driving depending on how hot it is or how hard I was driving. This is with the stock gauge.

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Frank W
90 5.0 LX Notchback Daily driver. MAC 2.5" cat back FMS aluminum driveshaft, MSD blaster coil, MAC shifter other stuff check out here user site

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74 Chevy Laguna Type S-3 Warmed over 305 upgrading to 454 soon

I understand that as an engine warms up the oil pressure will drop some. I just wasn't sure if 8-10psi was too low at idle when reaching operating temp... I appreciate the responses............I guess this may be ok for used motor w/some miles on it.