oil pressure

i have an 89 RS with 2.8 v6

and my oil pressure has been different lately, different than it was like a month ago, i recently found that i have been driving around for who knows how long with the OIL CAP OFF!!! i think my brother was putting in oil or something, so i noticed that oil pressure went back up. it usualy stays around like the top the line below the 90, but now it is always at the half of the gauge. the cap has been on ever since, but the oil pressure isnt what it always was like a month ago, think something is wrong? oil pump maybe? thanks




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<------- oil pressure was always in this area
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- <------- now its here, or below this area

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i dont know if this has anything 2 do with whats wrong or could be the answer but whens the last time u had a tune up? and check your belt and make sure its ok and your pullies are fine, my pully that the tention bolt is on locked up frieday and the damn belt flew off and i noticed that the oil and the battery gauge droped like silly, i added oil like a damn fool and didnt even notice that the belt wasnt on the pullies and right before i closed her up i noticed nothing was spinning and the belt was hanging from the water pump...smh. after i replaced it everything went back to normal settings. i guess its a long shot but maybe worth looking into.

havent checked the pulleys or anything like that, about the tune up.. i got all of my top seals replaced like 3 weeks ago, major oil leaks at the distributor, and valve covers, and basically all the top seals. my mechanic said i needed a new cap and rotor plugs and wires, i dunno if that has anything to do with it, i recently put on a new oil filter and changed the oil. the oil filster is right, it fits, did it in shop class and teacher looked over my work..... oil pan is tightened tight. but ill check the pulleys, anything to look for specific? i think the surpantine is like pretty much new, under a year old. thanks! :D

this was new to me but with the belt off you should be able to move your pullies with your hand i did that and got to one that didnt move but a inch, it was warped and it looked like something had chewed it up and spit it out. like i said im not sure if that could have anything to do with your problem but i did notice a change with my meter when the belt came off and when i fixed the problem it went back to normal. a 10 min job just to check it out, i guess its worth a look.

idk if this helps but my 350 runs like 65 at startup and 45-55 when hot at running speed..at idle hot its at like 25...so dont feel bad..is that bad by the way

Youll notice on that pressure guage that the top is red, kinda like the temp guage, and your tach, that means youre not supposed to be running that much pressure. My guess is that you had some sort of debris blocking an oil passage that was creating back pressure and when you changed the oil it was moved or fell away from the hole it was blocking. The oil pressure you are now running is normal and quite healthy. I wouldnt worry about it unless you start hearing a ticking sound that gets louder over time. 45-55psi for oil pressure is concidered normal.

On that note, also concider that something may be malfunctioning, if your oil pump isnt working, your engine is probly going to let you know either with a ticking sound, or metal shavings on the drain plug at your next oil change. If your oil pressure guage is indicating a problem, but there is no evidence to support it, you might have a faulty guage, or a bad oil pressure sensor. or bad wiring somewhere in the circuit. Just something to concider.