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88F150
New User
Oct 6, 2007, 9:12 AM
Post #1 of 3
(2493 views)
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erratic oil pressure
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This problem is with a 1988 Ford F150, 5.0 litre engine. I noticed recently, that the oil pressure gage would drop toward zero upon acceleration, and come back up to normal during deceleration or steady crusing. I pulled over and checked the oil level. It was normal. I assumed that the oil pressure sending unit was probably going bad, and ignored the problem. The next time I drove the truck, The gage seemed to work normally for about 30 miles, then stated acting as described previously, but this time it eventually dropped to zero and stayed there. The engine started loosing power. I was almost home at that point, so I pulled into the driveway and shut it down. The next day, I hooked up a temporary mechanical oil pressure gage that was known to work. Upon start up, the oil pressure immediately rose to about 35 psi, but dropped to near zero after about 5 minutes. This engine supposedly has only 86000 miles on it. Any ideas out there?
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Oct 6, 2007, 12:29 PM
Post #2 of 3
(2489 views)
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Re: erratic oil pressure
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Big trouble - don't drive it! Even the 35 cold is lousy. You felt it and verified it so it's real. This engine is possibly so sludged up it can't return oil or the pick up is plugged up. Does it consume any oil regularly? Qt. now and then is fairly normal with these engines.
If this thing still runs well and shows no sign of serious sludge (remove valve cover if you need to for a good clue) then the oil pump may have failed. Rare for that. Not sure what drives it but it might be the distributor - not sure. If so you could rig up a drill to what may be 1/4 inch socket (just checked a spare dist that would fit that) but absolutely don't lose a socket in there - use a dist shaft without the gear if you have to or make something up. If it behaves with a drill if that works at all the dist shaft might be a problem or the 1/4 hex down there?? The one I just checked was a hex not twelve point.
Oil pan on the double hump type which I think even the trucks used can come out without more than tilting the engine at least the ones in the cars. The ones I dealt with all were for rust problems in between the humps and salt and sand built up there and rotted out the pan to leaking! I've owned tons of these 5.0s and am parting out a car I've owned for years with 213K running just fine and body shot,
T
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88F150
New User
Oct 7, 2007, 8:33 AM
Post #3 of 3
(2479 views)
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Re: erratic oil pressure
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Thanks for your advice. What you said makes sense when combined with what I suspect about the history of the vehicle. I bought this truck a couple of years ago from the original owner (who I did not know personally). I made the mistake of not having the truck thoroughly checked out. The general condition reflects lack of regular maintenance and there are no repair or maintenance records. I changed the oil and filter right after I bought it and have only driven the truck occasionally since (aprox. 2000 miles). I checked a shop manual for this vehicle and found that it is a major pain to drop the pan. I did not remove a valve cover, but shined a flash light down the oil fill hole and poked around with a screw driver. It does look pretty slugged up. Given my having driven it some with extremely low or no oil pressure, the currently low cold start up pressure and the general condition of the truck, I'm inclined to just sell it as is and cut my losses. Another lesson in the School of Hard Knocks. Thanks again for sharing your expertise.
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