Oil Pressure Goes down w/ throttle
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From: Laguna Niguel, CA
Oil Pressure Goes down w/ throttle My scenario did not come up in any searches I could find.
My car now has about 145K MI on it and the past 6 months or so my oil pressure has started to fluctuate in a weird way.
When the car is warmed all the way up (at least 10-20 mins of driving) the oil pressure will rise with RPMs, but when I life the throttle and the motor starts to decelerate, the Oil Pressure will jump a few pounds.
My guess is that when I am accelerating, the lash between the rotors in the Oil Pump is somewhat big, but as I lift off the throttle the engine decelerates, causing the rotors to be sandwiched together in the opposite direction and minimizing the wear/lash.
It has also developed what sounds like a bottom end ticking noise from the valley area(most noticeable on the intake mounting bolts, just like a clock, but NOT the exhaust) that I could not quite pinpoint with my stethoscope except for ruling out the exhaust gaskets. It is not really loud, but still audible and could be similar to lifter tick except for the fact that it has not done this in the past. This has gotten slightly louder in the past week or so.
I realize it may be hard to understand exactly when is going on, but if anyone is still interested in helping me after this post, I can spend more time and give a more detailed explanation as I realize long posts can scare off some readers. I can also take a video of the ticking and the OP gauge while it moves up and down.
Any help/insight is greatly appreciated.
My car now has about 145K MI on it and the past 6 months or so my oil pressure has started to fluctuate in a weird way.
When the car is warmed all the way up (at least 10-20 mins of driving) the oil pressure will rise with RPMs, but when I life the throttle and the motor starts to decelerate, the Oil Pressure will jump a few pounds.
My guess is that when I am accelerating, the lash between the rotors in the Oil Pump is somewhat big, but as I lift off the throttle the engine decelerates, causing the rotors to be sandwiched together in the opposite direction and minimizing the wear/lash.
It has also developed what sounds like a bottom end ticking noise from the valley area(most noticeable on the intake mounting bolts, just like a clock, but NOT the exhaust) that I could not quite pinpoint with my stethoscope except for ruling out the exhaust gaskets. It is not really loud, but still audible and could be similar to lifter tick except for the fact that it has not done this in the past. This has gotten slightly louder in the past week or so.
I realize it may be hard to understand exactly when is going on, but if anyone is still interested in helping me after this post, I can spend more time and give a more detailed explanation as I realize long posts can scare off some readers. I can also take a video of the ticking and the OP gauge while it moves up and down.
Any help/insight is greatly appreciated.
Last edited by gun5l1ng3r; Nov 20, 2008 at 11:54 PM.
Thread Starter
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Joined: Mar 2004
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From: Laguna Niguel, CA
Sorry to revive this old post...
My car just started making even more noise tonight on the way home from school.
Which bearings might be going? The cam, rod, or main bearings?
I don't see how the load on the motor and bearings can decrease oil pressure unless the clearances tighten up as I let off of the throttle.
Is there anyway to tell if it is the bearings without taking the motor apart so I can catch it before a rod puts a hole in the side of my block, costing me thousands of dollars when I can just fix it now for a lot less?
I just changed the oil and don't have any for an oil analysis...
This is my only transportation and I am in my last semester before getting my Bachelor's degree and really need to get to school without worrying about getting stuck on the way to class.
Any and all help is appreciated, I know there are a lot of HELP! posts, but I can honestly say this is my first of a serious nature. I don't know what I would do without LS1Tech!
EDIT: The oil pressure is a lot lower on hot days when I have been driving for a long time (up to school) and at some points the OP will stay around 40 PSI(indicated) even as the motor goes from idle up to around 2K RPMs, but around 3K RPMs (The highest I go with my old motor) it will JUMP up to about 50 PSI...
My car just started making even more noise tonight on the way home from school.
Which bearings might be going? The cam, rod, or main bearings?
I don't see how the load on the motor and bearings can decrease oil pressure unless the clearances tighten up as I let off of the throttle.
Is there anyway to tell if it is the bearings without taking the motor apart so I can catch it before a rod puts a hole in the side of my block, costing me thousands of dollars when I can just fix it now for a lot less?
I just changed the oil and don't have any for an oil analysis...
This is my only transportation and I am in my last semester before getting my Bachelor's degree and really need to get to school without worrying about getting stuck on the way to class.
Any and all help is appreciated, I know there are a lot of HELP! posts, but I can honestly say this is my first of a serious nature. I don't know what I would do without LS1Tech!
EDIT: The oil pressure is a lot lower on hot days when I have been driving for a long time (up to school) and at some points the OP will stay around 40 PSI(indicated) even as the motor goes from idle up to around 2K RPMs, but around 3K RPMs (The highest I go with my old motor) it will JUMP up to about 50 PSI...
Last edited by gun5l1ng3r; Feb 6, 2009 at 12:05 AM.
Thread Starter
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From: Laguna Niguel, CA
But the fact that it stays about 40 from Idle to 2000 RPM then jumps up is what scares me.
I think the noise is a collapsed lifter. I am going to take off the valve cover and look for any pushrods that arent seated up against the rocker arms...
I think the noise is a collapsed lifter. I am going to take off the valve cover and look for any pushrods that arent seated up against the rocker arms...
Mine doesn't really start to pick up til 2000 either. I think it's just the way some of these cars are. I am running a Melling hi volume pump with the high pressure spring too. I wouldn't worry about it unless it starts to drop off then you know you have an issue somewhere.
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Thread Starter
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Joined: Mar 2004
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From: Laguna Niguel, CA
So I have pretty much narrowed the noise down to a bad/collapsed lifter. I haven't pulled the valve cover yet, but will be doing that tomorrow.
My next question is, if I have the heads milled (just a rebuild/refurb) say .015-.030 if they are not flat, what size pushrods will I need if I go with a ALL stock components?
This needs to be done as quickly as possible and stock seems the most value for reliability and mostly available at the local dealer.
With the heads milled, and a stock 1998 head gasket of ~.056 compressed, that makes the rocker about .15-.030 closer, thus I need a shorter pushrod for the replacement LS7 lifters to have the same preload. But the kicker is one poster from Texas Speed mentioned that the stock PR are not 7.400, so I don't know what size PR to get...
So the question is do I try and get a head gasket (once again has to be ordered and shipped) to make up the milled difference, or should I keep the tighter quench and run a shroter PR?
I don't know yet if I will be doing the work or have a shop (hopefully Strictly Performance) do it...
Once again any ideas or help is GREATLY appreciated!
My next question is, if I have the heads milled (just a rebuild/refurb) say .015-.030 if they are not flat, what size pushrods will I need if I go with a ALL stock components?
This needs to be done as quickly as possible and stock seems the most value for reliability and mostly available at the local dealer.
With the heads milled, and a stock 1998 head gasket of ~.056 compressed, that makes the rocker about .15-.030 closer, thus I need a shorter pushrod for the replacement LS7 lifters to have the same preload. But the kicker is one poster from Texas Speed mentioned that the stock PR are not 7.400, so I don't know what size PR to get...
So the question is do I try and get a head gasket (once again has to be ordered and shipped) to make up the milled difference, or should I keep the tighter quench and run a shroter PR?
I don't know yet if I will be doing the work or have a shop (hopefully Strictly Performance) do it...
Once again any ideas or help is GREATLY appreciated!
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