ibjamin

iTrader: (6)

My engine lost about 10-15 pounds of oil pressure. It used to make just under 40 at idle (hot) and a little over 40 at higher revs. Pressure really didn't go up much with revs.

Then it lost about 10-15 pounds at some point. Now at idle it makes 20-25 and never gets over 35 and that is after going to Mobil 1 15w50, which added about 5 pounds.

Is there something wrong with the bearings or do you think the pump might be going bad? It is a 99 LS1. Stroker, 6.1L, heads and cam. It has an oil cooler in the radiator but that was put on before the pressure problem. AFAIK the pump is stock 99LS1.

If it is the pump what would you recommend? LS6, LPE hi volume, Melling 296? I may be adding an Accusump to it also so there will be like 9-10 quarts of oil in the system.

Thanks,

George

heavymetals

iTrader: (3)

Are you sure it lost pressure, that is, you have measured it?

You could have a sensor failing which is not unheard of.

It is located on the top of the motor just behind the intake manifold.

ae13291

iTrader: (8)

i would also say failing sensor! do u notice any more noise coming from the motor?? like pushrods, etc

JHL88

if it is in fact your oil pump based on what you have id go with an SLP which is a modified melling 296

tatasta

iTrader: (24)

Idling at around 40 and staying at 40 at high rpms sounds strange first of all. Idling at around 25 and high rpms at 40 doesn't sound uncommon, especially with stock pump. 6 to 8 psi per 1000rpm is sufficient but not always desirable. May be worth taking it in and getting a "true" reading from a mechanical gauge. Just my opinion.

dug

iTrader: (10)

might be time for an oil change. change it and see if it helps

ibjamin

iTrader: (6)

Oil was changed when I went to the 15w-50. I'm positive that the guage is reading proper. I had the low pressure light come on slightly in the middle of the Carasel at Road America.

Which pump should I get?

Is it possible some bearing clearances have opened up? I can't think of anything else that causes a drop in OP.

Lt1Porsche

iTrader: (6)

First off if i was you I would get rid of that 15w-50 ****. Go to a 5w-30 or 10w-30. And use a good filter. NAPA GOLD series or K&N are good filters. Why would you use 15w-50 anyway?

dug

iTrader: (10)

werd

Zitty'sZ

iTrader: (29)

I would say your oil pump is the problem, it seems alot of 1999-2000 models have this problem. I have a 1999 z28 and it was doing the exact same thing yours is. I installed the SLP pump when I did my heads and cam and now it idles cold at 65 lbs and 50 lbs hot . Just change the oil pump and you should be fine .

ibjamin

iTrader: (6)

I put the 15W 50 in to get more pressure. The car is roadraced and the 10w30 I used was too low when it got hot. I'll try a new pump before anything more dramatic.

So which pump? I saw Lingenfelter sells a high volume pump for $90. Seems decent. Any others? Like I said, the car has an oil cooler and will be getting an Accusump also so there will be almost 10 quarts in the system.

dug

iTrader: (10)

15 50 will make things worse

stick 2 5w30

5_02ls1

iTrader: (20)

hahaha

well you raoad race it....sounds like you hasve lost a lil clearance throw in a new hv melling pump and the pressurev will return....and theres nothing wrong with 50 weight oil.....i run nothin but 40 in mine.....

oh and how many miles on the rotating assembly???

robertbartsch

my 99 gave up the oil pump in 2001 so I swapped in a high pressure unit.

GMs have this issue but the General refused to recall.

...swap it or loose you engine...

shoemike

iTrader: (25)

i have had this same issue for 30,000 miles.
and i installed a mechanical gauge in line,
and i have concluded that my stock sending unit/gauge is faulty.
i too road race a bit and have yet to spin a bearing.
change your sending unit first.
don`t bother changing your oil pump unless you
go with the melling hv 10296 or the gm hv 17801830

ibjamin

iTrader: (6)

The engine has 34K miles on it.

Viper

iTrader: (6)

My 99 oil pump died with 35K on the clock, cost me the motor in 2001 and GM refused to cover it under warranty. FWIW.

Camaro396

iTrader: (14)

It could be the sending unit, but its probably the pump. I did the meling high vol pump when I did my cam swap, it idles at like 50psi, and almost pegs when its WOT.

SILVERZZ28

iTrader: (3)

Does it make more pressure when cold? If so then how could it be the sending unit?