Low oil pressure
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Low oil pressure
Hi new to this forum (been watching for a while good info) Now i have a question. Rebuilt 4.9 EFI oil pressure ran fine for about 5 minutes then dropped. Changed pump ,sending unit worked at 2000 rpm and above. Put a gauge on it and oil pressure was low at best 10-18 lbs. Could this be bad bearings causing this problem or any other suggestion. New bearings pistons etc ? any help thanks.
Post Fiend
Joined: Jan 2005
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Low oil pressure can be caused by a number of things and excessive main and rod bearing clearances is certainly one of them. Can also be bad oil pump, bad/stuck pressure release valve or blocked oil pick-up gauze.
Hope this helps.
Hope this helps.
Post Fiend
Joined: Jan 2005
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Well the pick-up screen can be ruled out if the engine is just rebuilt. That leaves a stuck/defective pressure relief valve. There are othe possibilities. It is possible there is an internal crack in the block or possibly a gasket is on wrong somewhere or the oil pickup pipe is cracked or not attached correctly to the pump inlet. Maybe someone else will be able to pinpoint it better for you.
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From: wi
cut youre oil filter open and look for the flakes of death . little shinny flakes of metal will be evident if you lost some bearings ? does the motor sound like its carrying low oil pressure / noisy ?/ wuth only 18 pds of pressure i would assume you would hear some chatter .
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Cut the oil filter open,nothing but a few bits of crud from my hands changing oil pump. Cant figure this one out. The Engine sounds fine no knocks ,chatter, lifters quiet no rod noise no hard running noises.
The Engine sounds fine no knocks ,chatter, lifters quiet no rod noise no hard running noises.
Last edited by mattdottie; Mar 19, 2009 at 04:05 PM. Reason: forgot something
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did you take the block and head to a machine shop for the routine vating and magniflux check are you sure all galley plugs are in
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From: Sumter SC
Whe the engine was rebuilt did the cam bearings get replaced? Didn't do that on my 460 in '53 and had low pressure (15hot idle 30 hot run). Also had 71 with 302 that never ran over 20 psi hot run and idled at 5psi drove it for 8 years without a knock or rattle. Would sstill have it but was rammed from behind at 60 mph total.
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did have all parts machined .I believe all oil galley plugs are in. Only two that I know of, one in front one in rear. Maybe there is one that has escaped my eye.If you have locations i can check again. The shop put in the cam bearings and and traded me a remanufactured cam. My bad but did not check cam to bearing size (thing went in kind of easy).
Also I found a motor out of a 94 F150 same 4.9 but the wireing harness has a square plug instead of the four connectors,can the harness be swaped with my 89 or are there any mods that need to be done.(good deal 250$ 34,000 on rebuild)Thanks for all the help.
Also I found a motor out of a 94 F150 same 4.9 but the wireing harness has a square plug instead of the four connectors,can the harness be swaped with my 89 or are there any mods that need to be done.(good deal 250$ 34,000 on rebuild)Thanks for all the help.
Last edited by mattdottie; Mar 20, 2009 at 09:24 AM. Reason: Another question?
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