trans_am_31

iTrader: (51)

I just finished rebuilding an LS1 engine and it has low oil pressure when idling. When the engine is cold it sits at the 3/4 mark (about 60 psi) and then after 15 mins it goes down to the 1/4 mark (about 25-33 psi). As soon as I tap the throttle lightly, the oil pressure goes up to about 55 psi. When I turn off the engine, after about 5-10 min it starts to leak oil through the bellhousing/engine area.

I am using 10w-30 conventional oil. The engine sounds good, there is no knocking or clanking of any kind. Any ideas on what is wrong.

Pheonix

iTrader: (16)

I would check the rear crank cover seal. Maybe your galley plug is not fully seated. Pull your tranny and flywheel and check it out. Let us know whats up.

Trev_SS

iTrader: (17)

could also be your rear main crank seal that would cause you to loose pressure.

trans_am_31

iTrader: (51)

GUys, I pulled the cover and it appears the rear main seal is leaking. HOw far in is the galley plug suppossed to go in. It appears mine may be a little out. I'll post pics today. Any other suggestions? Thanks

moeZ28

iTrader: (7)

The galley plug will just kind of pop or click in. it should be pretty well flush with the back of the block.

DarkJuggalo

iTrader: (6)

id bet its a rear main

trans_am_31

iTrader: (51)

Guys, I replaced the rear main seal and it took care of the leaking problem.

I also replaced the oil pressure sending unit and checked to make sure the galley plug was installed correctly and the oil pressure still does the same thing. At startup pessure is at 3/4 and then after 20 min at 1/4 oil pressure.

Could it be the oil pump or o-ring, or maybe I should tear it apart and see what is wrong inside bearings-wise. The engine makes no abnormal noises.

Any suggestions or thoughts on what it may be.

Thanks

01z28auto

Did you measure your bearing clearances when you rebuilt it? A little too much clearance will run normal oil pressure when cold,but when things heat up and expand,pressure drops. I've had this problem myself on a gen.1 small block.

ls1leadfoot

iTrader: (1)

my bet is the pump or o ring....is it the original pump??

01Z0H6

iTrader: (63)

Could you have knicked a cam bearing...?
That happened to me ONCE!A terrible experience..

Hopefully it is your "O" ring.. Do yourself a favor and get a ported/shimmed oil pump...

It will be one year in Feb since my rebuild and my oil pressure holds steady @ 60-70 ps1 @ any given time.

Good luck, keep us updated.

JimMueller

iTrader: (9)

Did you build the motor on a stand? If so, it's hard to get the o-ring wrong. Did you inspect or clean the old oil pump, or buy new?

When I rebuilt my motor this summer, I basically had the same symptoms (except for the leak). I was using generic 10W30 conventional oil and whenever it would heat up the oil pressure would be right around 25-30psi (best guess from the stock gauge). After the break-in period, I reverted to German Castrol 0W-30 and now the hot idle pressure has risen to about 40psi. My bearing clearances were set a little loose, .0025-.0030 IIRC.

Everything I've read indicates you don't need to worry about that 20-30psi at hot idle so long as it comes up to around 40psi at cruise, and the more the merrier at WOT (within reason).

trans_am_31

iTrader: (51)

Guys,

I used the old oil pump, I did shimm it for more oil pressure. That is the reason I am a little concerned with the pressure, shouldnt it be higher?.

The o-ring I am pretty sure it went in correctly, I rebuilt it on a stand.

If after I am done checking the oil pump and o-ring the car still has low pressure, I will check the cam bearings. The cam bearings were installed by a machine shop, so I dont know if they are nicked, but a great possibility.

Thanks so much for your responses, I appreciate your help!!!

01Z0H6

iTrader: (63)

I vote cam bearings as i stated earlier.. A PITA, but then again, it could be much worse!

Good luck.. Let us know.

01ssreda4

iTrader: (96)

i heard gm said that a minimum of 7 psi at idle is acceptable. thats sounds like bs to me. i have never heard of oil psi that low.

trans_am_31

iTrader: (51)

Guys, my pressure went up a little.

It turns out I had the pcv vaccums all messed up. When I had the oil cap on it would drop in pressure at about 25psi idle and about 45psi when pressing the gas pedal lightly, it was actually hard to take the cap off since it was getting sucked in by all of the vaccum.

As soon as I take the oil cap off, the pressure shoots to about 40psi or a little under and about 60psi when the gas pedal is tapped lightly. The oil pressure goes down to about 22psi when the car gets hot and goes on an erratic idle and it wants to die, but then i guess the computer corrects the idle and up goes the pressure.

I changed the oil weight from 10w-30 to 10w-40 and the pressure now seems to sit at around 30-35psi. I guess its still a little lower than what it had when it was stock and working, but I guess its still an acceptable pressure. Even if I tap the gas pedal lightly the pressure goes up to about 60psi.

What do you guys think? Is this an acceptable pressure for a stock rebuilt LS1? Thanks!!!!

SPRAYED 01

iTrader: (22)

did you use a dual roller timing chain? If so and you used the spacer for the oil pump the spacer could be on up side down on the driver side which will block an oil passage and cause lower oil pressure. I did this once.

fastvet

iTrader: (2)

When I put a cam and heads on my ride, I got the same result. My brother has an ss and when he did the same install, the same thing happened. Then He put an ls6 oil pump and it solved the problem. It might had been the o-ring, but i have had my car idleing at 28psi for about a year and a hlf and have not noticed anything wrong with it since then. But it does get you thinking if you did anything wrong during the install. next time I tear aparrt the engine, i will be putting in the ls6 oil pump.

bczee

iTrader: (12)

Can you give details on what your PCV system is and what you found wrong ?..

Has the PCV system been modified? Are you using a Catch Can, Is the front valve cover air tube running to the Throttle Body ?

trans_am_31

iTrader: (51)

Thanks for the responses guys.

I didnt install a double roller timing chain. I will definitely check the oil pump later. However, if the pump wasnt working correctly, it wouldnt shoot up back to 60psi when tapped lightly, would it?

Yes, the pcv system was modified by the previous owner and I dont know how to fix it. He had a hose from the drivers side valve cover to the passengers back valve cover. From the front of the passenger valve cover he routed another hose to the side of the inatake on the passenger side and covered the throttle body with a plug. I know this has to be wrong. Maybe that can be the reason it idles erratically.

Anyone know how to make the pcv work. I am trying to buy a pcv system as we speak, otherwise I dont know how else to fix this. I have heard of a breather.

fastvet

iTrader: (2)

your right about a breather on both valve covers. thats what i got. but the surging sounds like a vacuum problem. check the back of the intake manifold and make sure the MAP is on right and make sure the two hoses that connect to the intake back there are connected. the suction problem you had, i expirienced the same thing when i took my egr **** off. then i re-routed the hoses and put breathers in and it solved the problem. hope this helps!