View Full Version : is my oil pump bad?


gc302047
01-26-2009, 08:34 PM
i have a 98 ls1 stock oil pump and when i start the car pressure seems good. around 35-40 psi but once the car warms up it drops to around 20-25. when im on the pedal the pressure never reaches 60 psi. im hoping its just the oil pump. can sombody help me out. it just recently started doing this.

9000th01ss
01-26-2009, 09:16 PM
Put a mechanical test gauge on it to check the accuracy of the stock gauge.
Or just take a chance and replace the sender.

ponygt65
01-26-2009, 09:30 PM
Put a mechanical test gauge on it to check the accuracy of the stock gauge.
Or just take a chance and replace the sender.

+1


What's the highest Psi you see under a good load/upper rpm?

gc302047
01-26-2009, 11:48 PM
50 psi the thing also ticks bad and you can hear it from underneath a lot better if you get underneath the car if that has to do with anything.

KENS_SS_4
01-27-2009, 08:25 AM
The number one reason for low oil pressure in older cars is the cam bearings being worn (many people change other bearings but neglect the cams bearings because they are harder to change). Next would be mains, piston journals and down the galley.

Pressure is low when the flow is high. The flow increases as the bearings wear.

Although this may not be true in your case, it is the general rule I go by.

SOMbitch
01-27-2009, 11:55 AM
Definitely check with a mechanical guage. The early LS1's are known for crummy oil pumps. Cross your fingers it's not bearings. How many miles???

Ls1Rook
01-27-2009, 12:04 PM
Mine was as bad as yours, i just changed oil and oil filter and it went back to normal

9000th01ss
01-27-2009, 12:17 PM
Wrong.
Bearing wear yes, cam bearing wear--NO.

Think about it, common sense.
Cam bearing oil feed hole on the bottom.
16 valve springs on the top pushing down (yes ken, not all at once, but they're pushing down) They're pushing the cam against the oil hole.
You've got maybe 60 psi though a 3/16 hole against 16 valve springs.
I think the vale springs win.

But thats your general rule. My general rule is the same except I choose main bearings.
Main bearing feed holes are on the top, and you've got several hundred horsepower (ok ken maybe 50 at idle) pushing the crank AWAY from the oil hole. Not to mention gravity.

Common sense determines my general rule, thats if I had one, I don't.

The number one reason for low oil pressure in older cars is the cam bearings being worn (many people change other bearings but neglect the cams bearings because they are harder to change). Next would be mains, piston journals and down the galley.

Pressure is low when the flow is high. The flow increases as the bearings wear.

Although this may not be true in your case, it is the general rule I go by.

gc302047
01-27-2009, 12:47 PM
Definitely check with a mechanical guage. The early LS1's are known for crummy oil pumps. Cross your fingers it's not bearings. How many miles???

121k and it has not been abused its whole life. it was driven by a 45 year old lady

shoemike
01-27-2009, 12:53 PM
From my experience with connecting a mech. OP gauge,
the line below 40psi is 35psi and the line above 40psi is 70psi.
unless you are in the red don`t worry about your OP.
For some reason people on this site think the LS1 needs to have 60psi OP
all the time.
High OP does not equal high flow.

9000th01ss
01-27-2009, 01:07 PM
From my experience with connecting a mech. OP gauge,
the line below 40psi is 35psi and the line above 40psi is 70psi.
unless you are in the red don`t worry about your OP.
For some reason people on this site think the LS1 needs to have 60psi OP
all the time.
High OP does not equal high flow.

Good info. But the guy said: . it just recently started doing this.

Maybe he just recently noticed.
Have you seen the book specs on LS1 oil pressure? It says something to the effect that 5 psi at 550 rpm idle is fine.

I do have a general rule on oil pressure: anything under 20 psi--theres usually a problem.

To help the OP with his OP :eyes: I'd go to a thicker oil and see what happens.

I was reading a google search on oil not long ago and ran accross this article.
It was about oil recommendations in some supercar type (lamborghini, or one of those)
He said the owners manual actually has a recommended oil viscosity chart based on vehicle useage, average oil temps, and mileage.
I agree that a thicker oil should be used with higher mileage. But the OP's concern about it happening suddenly makes me think there may be a problem.
Maybe a recent (or not so recent) oil change, viscosity change, filter brand change. These can all have a slight effect on oil pressure.

gc302047
01-27-2009, 09:01 PM
i did just recently change the oil and filter but why would it all the sudden start making that ticking noise once it warms up. i no the ls1 is known to sound like a sewing machine but i can hear it underneath the car and when im sitting in my car with the windows down and the ticking speeds up as the rpms increase.

the car definitely has a OP problem because if i drive the car hard up to 6000 once i slow down i smell oil burning and i see white smoke coming out of the tailpipes! i just dont know what to look at it could be a bearing problem but im no expert.

01ssreda4
01-27-2009, 11:23 PM
The number one reason for low oil pressure in older cars is the cam bearings being worn (many people change other bearings but neglect the cams bearings because they are harder to change). Next would be mains, piston journals and down the galley.

Pressure is low when the flow is high. The flow increases as the bearings wear.

Although this may not be true in your case, it is the general rule I go by.

he said it happened all the sudden not over time. the pressure spring in the pump is bleeding off prematurely and causing your pressure drop. simple.:chug: replace it.

98RedBird
01-28-2009, 03:56 AM
Sounds like EXACTLY what my 98 started doing a few years ago. I swapped the pump out and problem solved.

nemss1
01-28-2009, 02:19 PM
depends on if u are talking about a warm idle or not. if car is warm and pressure is at 20-25 at idle, i say its just normal

01ssreda4
02-03-2009, 04:19 PM
depends on if u are talking about a warm idle or not. if car is warm and pressure is at 20-25 at idle, i say its just normal

not true, some bleed off springs dont show fatigue until warm. giving a reasonable pressure on cold idle then falling off as the oil gets warmer.