Gambit69

Okay, this post is going to have a few pics with it so please be paitent when loading.

I have noticed my oil pressure is fluctuating a bit. It is pegged all the way up when I first start it up and I know this is normal but once it gets warmed up the pressure is here:


at this rpm:

Gambit69

but it will run at this pressure:


when I rev it to this rpm while in park:


but when I drive around and once i get cruising about around 1000 rpm, maybe a little higher or lower sometimes, it will sit here:

sometimes it will get lower when i get ready to park.

Is this normal running range? It is in the middle of winter and I am runing Valvoline Max life 10w-30. I just change the oil today and this is were it runs. IF anyone has any pics of their oil pressure gauge when their car is warmed up I would appreciate it or just mark on my pics where your pressure is at. I might have a small headgasket leak around one of the exhaust ports but no oil is getting in the antifreeze and no antifreeze in the oil so I dont know if this would be causing this to happen with the pressure. Any help would be greatly appreciated.

GroundPoundinZ

I don't think I'd worry about it if I were you. If it runs good and doesn't use oil, I wouldn't be alarmed by the oil pressure flucuation. My 88 IROC carries fairly low pressure at idle, and increases with increased RPM's too. I'm thinking the culprit may be the stock oil pump being kind of weak. My 97 GMC has the same tendencies, as does my father's 95 Z71. All of these vehicles run top notch so I don't think you should be worried about it.

GroundPoundinZ

Oh, one other thing...... I love the Max Life commercial with all the kids with messed up teeth. The poor dad's would-be car payment money is going to the orthodontist instead. LMAO

Cruzin Kaz

Most F body cars run at about 10psi when at idle, and climb to around 40 psi when undr load, or higher revs. After all the pump is workign more wiht higher RPM's. My TPI in my Monte SS runs at exactly 10psi for oil pressure at idle. Once I rev her up or go for a cruise etc. She climbs to 40-50psi. As long as your not hearing any ticking etc. I wouldn't be to concerned. Now some OEM guages do screw up in time. So you could always buy yourself a aftermarket oil guage to make you feel better.

hydric

the so called "rule" is 10 pounds of pressure for every 1k rpms.

joshwilson3

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llvll4l2c91350

easy to change the sending unit. it will either be mounted behind the distributor or down above the oil filter depending on year. just screws into the block.

ede

less that 10 dollars, screws out and screw the new one in, shouldn't have to remove anything to do it

joshwilson3

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hydric

you "should" buy an aftermarket mechanical gauge...

BLACK ICE

Good to know Im not the only on that apears to have crappy oil pressure my Formula my T/A and my Iroc all said I had low oil pressure but they didnt seem to act like they had bad oil pressure

ploegi

Back in "the day" (TM) GM could build an oil pressure sender that would last forever. Along in the early 80's, GM changed the design. Now, simply changing your oil can toast your sensor. Does this make sense????? H*ll NO! But, that is the way it is. What happens is the sensor gets an air bubble, that it can't get rid of, and, oil pressure guage acts really funny. Replace the sensor, and viola!!! works the way it is supposed to again.

My question is: If an air bubble in the sensor causes it to malfunction, why does replacing it solve the problem? It would seem to me that the new sensor, not having any oil in it, would also get the bubble, and NEVER work right......

Bottom line...... The "new" design pressure sensor is a peice of crap...... Replace it, and your gauge should behave better.

joshwilson3

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Gambit69

I have a few questions about the problem that I have. I was just able to get my car home since it has been snowing here like crazy. When I get the car warmed up and drive it home, about 15 miles, when I come to a stop it will read zero. The car runs fine, it just scares me that the gauge reads no pressure Now if there was actually no oil pressure wouldnt the car shut off since if the sendor is reading no pressure it would shut the fuel pump off? Just curious about that one

Another question is, do I have to drain the oil and take the filter off to change the sendor that is right above the filter? I dont want to have to change the oil since I just did that and the oil is still clean as when I put it in.

If i was to put in an aftermarket electrical gauge in the car, would I still be able to use the factory one or would it be useless now? I am thinking of getting a autometer cobalt oil pressure gauge if I have to to go with my other gauge. Any help on any of this is greatly appreciated. I will let everyone know how things turn out when I get the sender replaced.

llvll4l2c91350

you shouldn't have to drain the oil just let the car sit for a while.

you can also leave your factory sender where it is and mount the aftermarket one either in the hole behind the distributor and i think there's also one by the timing cover.

i have an auto meter gauge that it's still in the box. was gonna put it behind the distributor but i couldn't get the little square nut loose. decided to just stay with the factory one for now.

Gambit69

Well, it is about 11 pm here and I just got my new oil pressure sensor put in and let the car run for about 10 minutes and it looks like it has good oil pressure now. I will know more tomorrow after I do my running around tomorrow to see how it works. It wasn't that hard to change just had to find the time to do it and the right tools to do it with.

I have a question about the old sensor I took out. I noticed when I unplugged it, it looked like there was a little oil inside the plug. Is this normal to happen or could this be what made the sensor go bad. Just curious as all. I will let everyone know how things go tomorrow. Thanks everyone for the help on this. I greatly appreciate it.

joshwilson3

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Gambit69

It is a Borg Warner part and the number is S4086. I got it from O'Reily's and it cost me around $30.

Gambit69

Everything seemed to work just fine with the new oil pressure sensor. When driving it will run around 40 and when I come to a stop it will drop down to between 20 and 25. So I think everything is actually working better than before. Before it would be pegged all the time then when I come to a stop it would drop down to around 15 and now it actually fluctuates showing the different pressure. Thanks for everyones help.

joshwilson3

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Flamingo

Is there really a 'GM' sensor? Arent they just Borg Warner, Bosch, or similar? Just something to think about.

Leahs88irocz

what if theres some ticking?

m14mike

I've got the same problem with fluctuating pressure - putting the same sending unit in my 92 RS tommorrow. I always replace my factory parts with Borg Warner from O'riellys whenever possible. :rockon:

Mangus

I know this is a little old now, but I just wanted to post and say my car just started with the exact same symptoms this morning. Scared the heck out of me.

Normally my pressure is 30 at idle and around 60 at cruise. This morning it started at 30 and as it warmed up, the pressure dropped to about 25 at cruise. At idle it would drop to about 15 for a second, then plunge to 0 (YIKES!).

Oil looks good, engines not overheating. I'll be changing the sending unit tonight.

!!!

(I should note that the existing, original sending unit has 216k miles on it. Not bad!)