low oil pressure!!!!!
11-18-2005, 02:59 PM
#1
low oil pressure!!!!! Im so frustrated right now. We finally got the 402 fired up after finding out we forgot a darn ground wire on the back of the head! On the initial fire up all the guages were acting funny and we only showed about 10-15psi on the oil pressure. We didnt think much about it and shut it down. Today we went to start it up again and there was no oil pressure. If i tapped the gas, it would spike to 25-30psi and back down to 10-15 at idle. Everynow and then it would drop back to 0-5 and back up to 10-15!! What is going on here?!?!
Is it the o-ring on the oil pump?? Yes we did put it on there...is it possible it was over/under tightened? Is there anything I can check before we pull the front of this freakin thing back apart again?
Even if I do pull it back apart, what do I do....torque it down again just like I did before??
Is it the o-ring on the oil pump?? Yes we did put it on there...is it possible it was over/under tightened? Is there anything I can check before we pull the front of this freakin thing back apart again?
Even if I do pull it back apart, what do I do....torque it down again just like I did before??
11-18-2005, 03:16 PM
#2
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Oil Pressure. The following will cause oil pressure to be low:
1. A bad oil seal at the oil pump.
2. If any of the cam bearing move either forward or backward you can loose oil at that oil port. I have personally seen poor tolerances on new bearing that resulted in this problem within a few minutes of running. The pressure started out OK, but within just a few minutes, two of the bearings worked their way out of position. The result was low oil pressure and a pretty noise lifter train.
3. A bad or missing oil seal in the rear of the engine. Did you check this? You can access it by removing only the transmission.
4. Debree can get caught in the oil pickup screen and starve the pump for oil.
5. A bad pressure sending unit and/or a bad guage and/or something wrong with the wiring.
Have you:
1. Verified that you do indeed HAVE low oil pressure? Use a mechanical guage to verify pressure.
2. Do you have other low oil pressure symptoms? Is the engine noisy? Are your lifters noisy?
The above is pretty much everything, I have ever seen cause severe low oil pressure.
It is EXTREMELY unlikely that either undertightened or even less likely over tightened the retainer for the oil pump at the pickup tube. Overtightening will NOT cause the oil seal to get pinched. Even after properly torqueing the retainer, the pickup tube can move and is supposed to.
Sam
1. A bad oil seal at the oil pump.
2. If any of the cam bearing move either forward or backward you can loose oil at that oil port. I have personally seen poor tolerances on new bearing that resulted in this problem within a few minutes of running. The pressure started out OK, but within just a few minutes, two of the bearings worked their way out of position. The result was low oil pressure and a pretty noise lifter train.
3. A bad or missing oil seal in the rear of the engine. Did you check this? You can access it by removing only the transmission.
4. Debree can get caught in the oil pickup screen and starve the pump for oil.
5. A bad pressure sending unit and/or a bad guage and/or something wrong with the wiring.
Have you:
1. Verified that you do indeed HAVE low oil pressure? Use a mechanical guage to verify pressure.
2. Do you have other low oil pressure symptoms? Is the engine noisy? Are your lifters noisy?
The above is pretty much everything, I have ever seen cause severe low oil pressure.
It is EXTREMELY unlikely that either undertightened or even less likely over tightened the retainer for the oil pump at the pickup tube. Overtightening will NOT cause the oil seal to get pinched. Even after properly torqueing the retainer, the pickup tube can move and is supposed to.
Sam
11-18-2005, 03:21 PM
#3
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Ugh, that sucks. It could be the oil pump o-ring or the oil galley plugs in the back of the block. Did you ever change or check the oil? I know you had starting problems before and you could have contaminated the oil real bad with gas with the repetitive cranking.
When you tighten the oil pump o-ring bolt it's critical the oil pickup tube is 100% completely seated into the oil pump before you tighten the bolt. In other words; set the o-ring on the pickup tube and do not use the tightening process to pull or seat the two together. I also remove the front oil pump cover (with pump in place on the block) and the two gears so I can see if the o-ring is pinched or crimped.
Another option would be to check the oil pressure with a mechanical gauge to verify true oil pressure. I would also verify you do not have electrical gremlins causing a bad gauge reading.
When you tighten the oil pump o-ring bolt it's critical the oil pickup tube is 100% completely seated into the oil pump before you tighten the bolt. In other words; set the o-ring on the pickup tube and do not use the tightening process to pull or seat the two together. I also remove the front oil pump cover (with pump in place on the block) and the two gears so I can see if the o-ring is pinched or crimped.
Another option would be to check the oil pressure with a mechanical gauge to verify true oil pressure. I would also verify you do not have electrical gremlins causing a bad gauge reading.
11-20-2005, 10:19 AM
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KD has a set of fittings that allow you to put a mechanical guage (incl) on in place of the oil filter and measure the oil pressure accurately. Part nos is like KD-3289 and avail for $120 online.
I, too, have low oil pressure.....15 # at idle and 24# at 2000 rpm. All this after 3000 miles of trouble free normal oil pressure driving on the 402.
I have checked and replaced in order:
1st. pulled the filter and cut it open....no metal or debris;that seemed good.
2nd. pulled the oil sensor and the oil filter fitting and checked the pressure relief valve at the oil filter....that was good.
3rd. Pulled the front cover....way ez, just read LS1HowTo.com. and replaced the oil pump and oring and blew out the pickup tube with comressed air, and check front oil galley plug while the cover is off.
4th. buttoned it up. Still low oil pressure.
5th I have 2 guages off the oil pressure sender, but as a last gasp effort I bought the KD guages. Will check the oil pressure on that guage today.
If that shows low oil pressure and I expect it to. The motor gets pulled and sent to an engine builder to redo the bearings and/or check the oil galley plug in the rear of the block.
Perry
I, too, have low oil pressure.....15 # at idle and 24# at 2000 rpm. All this after 3000 miles of trouble free normal oil pressure driving on the 402.
I have checked and replaced in order:
1st. pulled the filter and cut it open....no metal or debris;that seemed good.
2nd. pulled the oil sensor and the oil filter fitting and checked the pressure relief valve at the oil filter....that was good.
3rd. Pulled the front cover....way ez, just read LS1HowTo.com. and replaced the oil pump and oring and blew out the pickup tube with comressed air, and check front oil galley plug while the cover is off.
4th. buttoned it up. Still low oil pressure.
5th I have 2 guages off the oil pressure sender, but as a last gasp effort I bought the KD guages. Will check the oil pressure on that guage today.
If that shows low oil pressure and I expect it to. The motor gets pulled and sent to an engine builder to redo the bearings and/or check the oil galley plug in the rear of the block.
Perry
Last edited by Perry Kincy; 11-20-2005 at 10:27 AM.
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11-23-2005, 06:55 PM
#8
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I am Black8banger's dad. Thanks so much for your help so far. We have been struggling with this oil pressure problem for too long now and really want to run this car before winter sets in and the track closes. Let me throw in a few thoughts and get any suggestions from the group. We have no oil pressure on startup but the pressure comes up once the throttle is pressed. Let off the gas and it goes back to zero. The engine sounds ok but is very loud (typical) with the headers and exhaust that is on the car. We will check the pressure sensor. If the plug on the rear of the block is out, would you show oil pressure with increased rpms or would it stay at zero? I am trying to save some time, which we have very little of, by going to the most likely problem area first. One of my LS1 books says to apply JB Weld to the rim of this plug to keep it in. Any thoughts on this? Again thanks for all your replies and suggestions. My best buddy and I appreciate it !!!
11-23-2005, 11:20 PM
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I wish I could help more. If you have gone through the steps I have, you are left with the rear galley plug and/or internal damage.....bearings probably. The rear galley plug, I believe you can get at by pulling the tranny, but I am going to skip that and drop the motor.
I did check my pressure with the KD guage this evening and it was still way low as I expected.
So I now will have the motor pulled. All the other I did myself, but I have a 4 post lift and the motor really needs to be dropped using a 2 post. I use Combination Motorsports for that work in Las Vegas and they are way busy til early/mid December. So my car will be down for a while.
I wish I knew someone reliable here in Phoenix, but not only do they have to be good enough to pull the motor but to also freshen the motor. And that is a tuff combo.
I certainly would try the things I went through before you pull the motor as the front cover and oil pump are really ez to do. Probably the only trick is getting the new balancer bolt to rotate 140 degrees. And that is way hard. I used my jack handle as a 6 foot cheater bar and got it done without a problem.
Perry
I did check my pressure with the KD guage this evening and it was still way low as I expected.
So I now will have the motor pulled. All the other I did myself, but I have a 4 post lift and the motor really needs to be dropped using a 2 post. I use Combination Motorsports for that work in Las Vegas and they are way busy til early/mid December. So my car will be down for a while.
I wish I knew someone reliable here in Phoenix, but not only do they have to be good enough to pull the motor but to also freshen the motor. And that is a tuff combo.
I certainly would try the things I went through before you pull the motor as the front cover and oil pump are really ez to do. Probably the only trick is getting the new balancer bolt to rotate 140 degrees. And that is way hard. I used my jack handle as a 6 foot cheater bar and got it done without a problem.
Perry
