View Full Version : uber high oil pressure


jfrc2000
03-10-2010, 08:53 PM
i'll make this as short as possible. when this motor was built, it originally had almost no oil pressure. when the motor got hot, it was closer to 0. so i swapped in a melling oil pump, it helped some.
therefore i eventually pulled the motor, tore it down, and found the machine shop installed the cam bearings incorrectly. :mad: so new machine shop and new bearings. before reassembly, i DID recheck clearances, and it was good.
so re-rebuilt motor back in car, oil pressure at idle is 120-130 lbs! tired of working on it, i haven't driven it much.
so finally, swapped the stock ls6 ported pump this past weekend. well you guessed it, oil pressure is still 130 lbs. WTF?! is it a bad sending unit? before everybody says to check it with a mechanical guage, i would have if I knew anybody or had access to one.
i'm really tired of all this work and going in circles- there's plenty of other things i'd rather work on or spend money on. any ideas or suggestions would be great

livefast1
03-11-2010, 12:03 AM
dude go pick up a cheap sunpro mechanical oil pressure gauge for 30 bux and use that to check it, you don't need an expensive one. i can't see the pressure actually being that high at idle, you would most likely rupture the filter or at least shoot past the seal.

jimmyblue
03-11-2010, 09:44 AM
I don't know where the pressure relief spring /ball is on
these motors, but there should be one. Maybe the oil pump
is a "high pressure / high volume" one, and "high" is too
high. Or maybe the relief path is simply messed up.

ryarbrough
03-11-2010, 10:26 AM
What are the clearences on the bearings. Some of the melling pumps are supposed to be used only with "race" engines with looser tolerences in the main/rod/cam bearing area.

jfrc2000
03-11-2010, 03:07 PM
it has been awhile since i rebuilt engine, but with plastiguage it was right in the middle of the tolerances

whether it was the high volume melling, or the relief check inside, that is why i tore it apart to swap back to the stock ls6 pump- and it still is 130 lbs at idle

and the melling does flow @ 20% more, but both are supposedly producing the same pressure?!

ryarbrough
03-11-2010, 03:16 PM
If it flows 20% more and the journal clearences are tight, that extra 20% has nowhere else to go, making pressure rise. If that is the case I'd be willing there's some crazy cavitation going on in the pump though. I'd check with a manual gauge first and see what that tells you. I'd be very surprised if that didn't hurt a seal somewhere if the pressure really is that high...

billy.johnson
03-11-2010, 05:36 PM
I had the same problem on my gto and it was the sending unit. good luck

XtraCajunSS
03-12-2010, 02:00 PM
You're not making 130psi at idle with an LS anything and a stock type pump. I've had the same issue on multiple cars and it always comes down to the sender. Double check your pressure with a mechanical guage and with a Melling you should see approx 60psi cold depending on clearances. FWIW, I've used Melling HV's on almost everything with no ill effects. In my experience, you really can't have too much oil pressure in an LS engine.

Shane

Ryneman
03-14-2010, 03:43 PM
Just got done reading the post and all the replies. I will be changing my sending unit just for good measure and installing a melling HV(p/n 10295) in my build.

And a 130 lbs of pressure??? you should have oil going all ove the place, if it really was that high. Good luck, I hope changing the sender unit works out.

black98ws6ta
03-14-2010, 04:43 PM
Corvette? Bad sending unit.

rsz288
03-15-2010, 03:26 AM
That is a lot of posts you will need :). LOL.



Shane
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1 FMF
03-17-2010, 02:12 PM
what kind of oil pressure gauge do you have that's telling you over 100 psi?
The gauge in the dash only goes to 80, and i haven't seen any aftermarket gauges over 80psi not that i would remember if i did,
if you did have 120+ psi oil pressure I would think you would see evidence of that by the oil filter casing bulging outward some,
and the oil pressure relief valve is on the oil pump, the only way to get high pressure like you describe is for that relief valve to stick closed. And even at idle or low rpms the pump isn't spinning fast enough to build over 100 psi, if it did then there would have to be near zero oil flowing through the bearings, lifters and up the pushrods.
so yeah, check the sender first. the wire or sender is probably shorting to ground which is pegging the gauge. And the oil pressure relief valve on most of the LS1 pumps is set at 70 psi last i knew, so if that relief valve is working there is absolutely no way you can have an increase in oil pressure at your oil pressure sender (unless the laws of physics are different in your engine).

elias_799
03-28-2010, 10:07 AM
i have a melling 296 high volume/hi pressure and the most i see is 75psi at cold idle with 15w40 oil

Verde
09-15-2012, 07:42 PM
Hello,
I'm fairly new to this site and it may be the first time I've posted with an issue. I have an Ultima GTR (http://www.ultimasports.co.uk/Default.aspx) and it has a factory LS7 crate engine bolted to a Porsche 993 transmission. I purchased the car from it's builder/driver who ran it at Sebring and used it on the streets of Florida. It now has about 5K miles on it and it's a great car.
The problem is that the oil pressure reads wild high. The car has a RacePak digital (LCD) street panel for the instrument panel and presumably the matching RacePak senders and harness. Pressure at startup idle read 95lb's and when cold, and rev'ing of the engine (to 3000 for example) yields a pressure of over 100lbs. Once warmed up, at 70 mph at 2200 rpm it reads 94lbs and any time I put my foot in it it reads over 100lbs. The peak I've seen is about 109lbs.
When warm, it idles in the 55-65lb range.
Seems to me that this is way too high. The previous owner was concerned, called Chevy and was told that some early runs just run that high. He's a straight up guy and an excellent and perfectionist tech, so I doubt that he'd leave it that way for his use, and would not hand it off to me with some story.
So, I need help here. Should I install a mechanical gauge to check the pressure? Where does that get inserted and what gauge should I use? If it still reads high, what are my options. I really am concerned about a catastrophic failure so I drive it only gently - which is not what a great CanAm-styled sports car with a great engine was designed to do.
Thanks in advance,
V

rsz288
09-15-2012, 09:57 PM
Have seen these aftermarket dashes read incorrectly vs the factory sensors - and not just oil pressure. Also temp, rpm, speed. Unclear why.

Best to get an OBDII reader and take a look at what the factory sensor says.

Sure is a waste of power generating that oil pressure if it is for real. Either very high volume pump or tight clearances or both, if its not the calibration of the pil pressure readout.

Hello,
I'm fairly new to this site and it may be the first time I've posted with an issue. I have an Ultima GTR (http://www.ultimasports.co.uk/Default.aspx) and it has a factory LS7 crate engine bolted to a Porsche 993 transmission. I purchased the car from it's builder/driver who ran it at Sebring and used it on the streets of Florida. It now has about 5K miles on it and it's a great car.
The problem is that the oil pressure reads wild high. The car has a RacePak digital (LCD) street panel for the instrument panel and presumably the matching RacePak senders and harness. Pressure at startup idle read 95lb's and when cold, and rev'ing of the engine (to 3000 for example) yields a pressure of over 100lbs. Once warmed up, at 70 mph at 2200 rpm it reads 94lbs and any time I put my foot in it it reads over 100lbs. The peak I've seen is about 109lbs.
When warm, it idles in the 55-65lb range.
Seems to me that this is way too high. The previous owner was concerned, called Chevy and was told that some early runs just run that high. He's a straight up guy and an excellent and perfectionist tech, so I doubt that he'd leave it that way for his use, and would not hand it off to me with some story.
So, I need help here. Should I install a mechanical gauge to check the pressure? Where does that get inserted and what gauge should I use? If it still reads high, what are my options. I really am concerned about a catastrophic failure so I drive it only gently - which is not what a great CanAm-styled sports car with a great engine was designed to do.
Thanks in advance,
V

Verde
09-16-2012, 06:55 PM
Thank you for the response.
Will the OBDII read any differently? Doesn't it rely on the same sensor? Does your hypothesis assume that the sensor is alright and it is the display that is incorrect? Just want to make sure I'm following you and that I'm testing for the right thing.
V

Have seen these aftermarket dashes read incorrectly vs the factory sensors - and not just oil pressure. Also temp, rpm, speed. Unclear why.

Best to get an OBDII reader and take a look at what the factory sensor says.

Sure is a waste of power generating that oil pressure if it is for real. Either very high volume pump or tight clearances or both, if its not the calibration of the pil pressure readout.

ZTwentyAteU
09-16-2012, 10:48 PM
cheap oil pressure gauge from parts store. do it

60psi is fine. Ive seen 80 on cold starts plenty of times