low oil pressure
05-03-2006, 09:40 AM
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low oil pressure i have a question. i have a 99 z28 auto with 92k miles on it and my oil pressure gauge will be at 40-50 at cold start, then driivng around town it will be about that till it gets hot, when its hot idle it drops to about 18-20psi. when i start moving it goes back up and when i floor it it goes 50-60 all the time.
what could the problem be, i am assuming it might be the bearings stretching out.....?
what could the problem be, i am assuming it might be the bearings stretching out.....?
05-03-2006, 09:48 AM
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as long as it's only low at idle, I wouldn't worry about. The general rule of thumb is you want 10psi for every 1000rpm, so aslong as when the rpm's go up, the pressure comes up, i wouldn't sweat it too much. 
05-03-2006, 09:49 AM
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mine does the same thing, but doesnt get lower than 30 PSI. I think its the oil pressure sending unit going bad and im gonna replace it when i get my LS6 intake this summer. might also want to consider using a heavier oil considering the hotter the oil gets the more it thins out and less pressure you get, what weight oil are you running 5w-30 or 10w-30??? also are you running synthetic or regular oil??
05-03-2006, 09:54 AM
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i have a 10-30 or 10-40 in there right now, it was either 5-30 or 10-30 before and i bumped it up a tiny bit this last oil change. i have been spraying the car for about 30k miles or so.
05-03-2006, 10:10 AM
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does the car feel funny or act like its gonna die?? if your that worried about it just get a LS6 oil pump ported or unported either one is good and see if that fixes it, but as long as you have good pressure while driving then i would say its normal.
05-03-2006, 10:15 AM
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no, it acts fine, still pulls really well, i havent sprayed it in a while. i have a brand new ls6 pump that i am going to install once i get a chance.
the only thing i am worried about is blowing the motor or spinning a bearing. i plan on spraying it more and probably pushing more power soon.
the only thing i am worried about is blowing the motor or spinning a bearing. i plan on spraying it more and probably pushing more power soon.
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05-03-2006, 10:24 AM
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I had the same problem. Mine would drop to about 30 at idle also my car has 134000 on it .I changed the oil from mobil 10/30 to mobil 15w/50 seemed to help. The pressure now doesn't drop below 40psi.and at cold start it registers about 60psi and when driving it is at 50psi or 55psi.
05-03-2006, 10:49 AM
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Don't worry. Surprisingly enough, gm specs call for at least 5 or 6 psi at hot idle. I know it sounds really low, but thats what it is. I had some oil pressure issues myself, but if its above that number and it builds pressure with rpms its fine. If you really want to be sure you should have it checked with a mechanical gauge at a shop. Its not cheap though.
05-03-2006, 10:59 AM
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Originally Posted by 1BDWS6
as long as it's only low at idle, I wouldn't worry about. The general rule of thumb is you want 10psi for every 1000rpm, so aslong as when the rpm's go up, the pressure comes up, i wouldn't sweat it too much.
05-03-2006, 04:34 PM
#15
ok heres the deal, my engine was just doing the same thing, ive got a 99 ta so its the same year motor and all. gm had problems with the 98-99 oil pumps and with that many miles id drop the pan and see what else is going on, dont let people tell you its normal to idle that low, because its not. i took my car in to a guy i trust and have known for a while (hes also got a 383 97 camaro) and i told him what my car was doing, basically the same as yours. he dropped the pan and is now recommending i get a new motor, which sucks buts ok cause i have a warranty, if theres not enough oil going through your internals your engines gonna blow esp. with all those miles.....get it checked
05-03-2006, 11:19 PM
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Originally Posted by staringback05
ok heres the deal, my engine was just doing the same thing, ive got a 99 ta so its the same year motor and all. gm had problems with the 98-99 oil pumps and with that many miles id drop the pan and see what else is going on, dont let people tell you its normal to idle that low, because its not. i took my car in to a guy i trust and have known for a while (hes also got a 383 97 camaro) and i told him what my car was doing, basically the same as yours. he dropped the pan and is now recommending i get a new motor, which sucks buts ok cause i have a warranty, if theres not enough oil going through your internals your engines gonna blow esp. with all those miles.....get it checked
Yes, they do typically hold lower operating oil pressure than the later models do, but I highly doubt its a bearing problem. 18-20psi at idle for any v8 is just fine. As long as it goes up when you get off idle, its not a problem. the later pumps have higher pressures, but thats because they are designed too!
I'd look at the sending unit before tearing apart the motor.
05-04-2006, 02:10 AM
#18
Originally Posted by jswelburn
The problems with the oil pumps on the early models were premature failures (as in, typically only a few months out of the factory and very low mileaged). Everyone says that they have a bunch of problems, and people with the older cars should change their oil pumps immediately, but no one ever posts with actual problems. Its a misinformation frenzy with no real basis to it.
Yes, they do typically hold lower operating oil pressure than the later models do, but I highly doubt its a bearing problem. 18-20psi at idle for any v8 is just fine. As long as it goes up when you get off idle, its not a problem. the later pumps have higher pressures, but thats because they are designed too!
I'd look at the sending unit before tearing apart the motor.
Yes, they do typically hold lower operating oil pressure than the later models do, but I highly doubt its a bearing problem. 18-20psi at idle for any v8 is just fine. As long as it goes up when you get off idle, its not a problem. the later pumps have higher pressures, but thats because they are designed too!
I'd look at the sending unit before tearing apart the motor.
05-04-2006, 02:15 AM
#19
Originally Posted by z28racer
i have a 10-30 or 10-40 in there right now, it was either 5-30 or 10-30 before and i bumped it up a tiny bit this last oil change. i have been spraying the car for about 30k miles or so.
05-04-2006, 07:47 AM
#20
when I ran mobil 1 5w30, I found the oil thinned too much. I was loosing quite a bit thru the pcv system.
I switched to german castrol syntec 0w30 and my oil pressure is consistent from cold to warm. My oil consumption is practically non existant now (mobil 1 had me loosing 1 quart/1500 miles). My reading today is the same as when I put in the castrol last year and I've managed almost 3k of driving since then.
Remember that sticking in a thicker oil will increase your oil pressure BUT putting in a thicker oil WILL slow down the rate of flow. A lot of people tend to use oil pressure as a indicator of good lubrication, its certainly a warning sign as to if you are getting any lubrication at all, but don't sit cozy thinking that's the end all to it. At least with the german castrol, you still get the flow of a 30 wt., sticking in a 15w50 or something similar may jump your pressure, if you've done a rear gear diff fluid change you will understand that thicker oils require more pressure BUT flow much less...
if you are that worried, I'd get it checked by a mechanic properly.
I switched to german castrol syntec 0w30 and my oil pressure is consistent from cold to warm. My oil consumption is practically non existant now (mobil 1 had me loosing 1 quart/1500 miles). My reading today is the same as when I put in the castrol last year and I've managed almost 3k of driving since then.
Remember that sticking in a thicker oil will increase your oil pressure BUT putting in a thicker oil WILL slow down the rate of flow. A lot of people tend to use oil pressure as a indicator of good lubrication, its certainly a warning sign as to if you are getting any lubrication at all, but don't sit cozy thinking that's the end all to it. At least with the german castrol, you still get the flow of a 30 wt., sticking in a 15w50 or something similar may jump your pressure, if you've done a rear gear diff fluid change you will understand that thicker oils require more pressure BUT flow much less...
if you are that worried, I'd get it checked by a mechanic properly.