odd oil pressure behavior
Thread Starter
Joined: Jan 2002
Posts: 4,069
Likes: 74
From: Casselberry FL
odd oil pressure behavior With the engine cold, the pressure starts at around 45psi. Driving through the parking lot at ~15-20MPH it rises to 60psi. Driving home it variesd between 50-ish and 65-ish. Going up a gradual hill it went up to 80 pretty rapidly, but stabilized back around 60 on level ground and descending the hill.
Checked the level and it was about a quart low. I drove to pick up some oil and the level stayed peaked at some random point above 80. I added oil to the middle of the hash marks. Upon starting the pressure was about 70-80. Driving through the parking lot after a few seconds the pressure dropped to ~45psi in a split second. However, on the street it rose back to 60-ish. Very short drive home but that was the highest it got.
I have the stock oil pump. I did try a longer drain interval this time. I normally run 4-5K between oil changes, but it's been 6-7K right now, adding oil as needed.
Thoughts on the reason for the odd behavior?
Checked the level and it was about a quart low. I drove to pick up some oil and the level stayed peaked at some random point above 80. I added oil to the middle of the hash marks. Upon starting the pressure was about 70-80. Driving through the parking lot after a few seconds the pressure dropped to ~45psi in a split second. However, on the street it rose back to 60-ish. Very short drive home but that was the highest it got.
I have the stock oil pump. I did try a longer drain interval this time. I normally run 4-5K between oil changes, but it's been 6-7K right now, adding oil as needed.
Thoughts on the reason for the odd behavior?
Thread Starter
Joined: Jan 2002
Posts: 4,069
Likes: 74
From: Casselberry FL
The pressure isn't low...it's too high. From what I've heard a bad oil pump will cause low pressure...?
It stayed around 80psi driving to work this morning. I had the oil & filter changed over lunch. Driving there I was idling with it at ~65psi, and within a split second it drops to a steady 45-ish. Never goes lower than that unless I let the RPM's fall too far below idle. Appears to be no change in behavior after the fluid/filter change.
I ordered a replacement sending unit and the LS6 PCV stuff. Might as well take care of it simultaneously.
Outside of the pump, what else can I check? Can I check voltage somewhere with my multimeter, etc?
It stayed around 80psi driving to work this morning. I had the oil & filter changed over lunch. Driving there I was idling with it at ~65psi, and within a split second it drops to a steady 45-ish. Never goes lower than that unless I let the RPM's fall too far below idle. Appears to be no change in behavior after the fluid/filter change.
I ordered a replacement sending unit and the LS6 PCV stuff. Might as well take care of it simultaneously.
Outside of the pump, what else can I check? Can I check voltage somewhere with my multimeter, etc?
TECH Fanatic
Joined: Mar 2002
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From: Your Reality Check Bounced...
80psi oil pressure...****...I'd say your GAUGE or sending unit is at fault...no way a stock 98 pump is pumping out a constint 80PSI....I'd replace the Sending unit, then the gauge if it doesn't start acting right..then..go for the pump.....try the easy stuff 1st...before tearing into the front of the motor.
Look simple advice from someone who's had oil pump failure....BUY A NEW PUMP! I paid $69 bucks for mine but i think they cost closer to $100. Its that or your gunna be out several grand to rebuild the whole motor....and thats if you do it yourself and don't pay someone to pull it and rebuild it for you. It is possible for these guages to be less than accurate but with the 98 pump and all the trouble they had with them, just get a new one and find someone to help you put it in now.
TECH Fanatic
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From: Your Reality Check Bounced...
I've got a 99 Pump....stock pump...change my oil every 1500 miles with RP 10w30 in the winter and 10w40 in the summer. If his gauge is showing that much PSI I highly dout it's the pump...the sending unit doesn't cost much and the gauge it'self isnt that expensive. it's not like you can't do one...see if the problem goes away..do the other and have ur answer in a days time. If neither work then get a nice ported LS6 pump from MIT, or LG Motorsports....
I am not saying the pump is bad, but changing those to simple things are quick easy and cheap before you tear into something that can take a weekend and a few 100 dollars to do.
Just my suggestion....
I am not saying the pump is bad, but changing those to simple things are quick easy and cheap before you tear into something that can take a weekend and a few 100 dollars to do.
Just my suggestion....
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Thread Starter
Joined: Jan 2002
Posts: 4,069
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From: Casselberry FL
I didn't realize you could buy the gauges separately. Helms just says 'replace instrument cluster'...guess that's how GM makes their money.
I'm going for the easy stuff first. What can I use to remove the sensor and tighten it back down? It looks like they have a special tool for this.
I'm going for the easy stuff first. What can I use to remove the sensor and tighten it back down? It looks like they have a special tool for this.
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Verdad Gallardo TECH Fanatic
Joined: Mar 2002
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From: Your Reality Check Bounced...
the sensor will come off w/a deep socket 5/8th...it's on the back of the block so taking the intake off will be ur biggest pain....10mm sockets for that..don't try and get them all the way out...just get them loose then pull the intake forward and becareful........
Thread Starter
Joined: Jan 2002
Posts: 4,069
Likes: 74
From: Casselberry FL
What a concept...I haven't lost that particular socket. I've had the intake off a few times, so I'm familiar with it's pecularities.
Thanks for the tip! (You too, Richie, although I don't know where your posts went!)
Thanks for the tip! (You too, Richie, although I don't know where your posts went!)
