Yet another low oil pressure thread
Yet another low oil pressure thread So I've read the other threads and am not sure where to begin. I just rebuilt my motor and am using a Melling HP pump. Starting the car cold, the pressure will idle at about 40. Once I start driving the car, the pressure drops until it's just above 0. Once back around idle, it goes back up to around 10. Based on this, what could the issue be?
Based on what I've read it could be
-A pinched o-ring
-I did not center the pump with feeler gauges
-The dumbell could be messed up. I pulled it out and looked at it before putting the motor in the car and it looked fine.
-The factory gauge/sender unit it bad. I doubt the gauge is just wrong because I'm getting good pressure when cold.
Anyone have any helpful info and/or links? Thanks
EDIT: I took the car back out and watched the gauge more closely. It held about 20 as I drove around but would drop to just about 0-5 when coming to a stop under no load.
Based on what I've read it could be
-A pinched o-ring
-I did not center the pump with feeler gauges
-The dumbell could be messed up. I pulled it out and looked at it before putting the motor in the car and it looked fine.
-The factory gauge/sender unit it bad. I doubt the gauge is just wrong because I'm getting good pressure when cold.
Anyone have any helpful info and/or links? Thanks
EDIT: I took the car back out and watched the gauge more closely. It held about 20 as I drove around but would drop to just about 0-5 when coming to a stop under no load.
Last edited by FNSlow; Jun 15, 2012 at 08:03 PM.
I pulled the o-ring out, looked fine but I still used the green ring because some people said to try it. Car still starts cold @ 20. What's next? Pull the trans, clutch, flywheel, and rear cover to check the dumbell?
Replaced the dumbell, still 20 psi cold start, only let it run a bout 15 sec. Replaced the filter, 30 psi cold start, still only ran it for 30 sec. WTF, why would the filter with 5 miles restrict that. It's still low so that's not the main issue.
I've never broken in a motor so I'm not sure how much metal should be in the oil but it seems like a lot. The filter is drying but I'm curious if there was enough metal to clog the filter since it jumped 10 psi with a new one.
Also ran the car with the front cover off. No oil coming out of the galley plug and plenty of oil getting to the front main bearing. So all I can guess is either clearances are loose and I need to try thicker oil or the brand new bearings are going. Can I pull the valley cover to see if the cam bearings are where they should be?
Also ran the car with the front cover off. No oil coming out of the galley plug and plenty of oil getting to the front main bearing. So all I can guess is either clearances are loose and I need to try thicker oil or the brand new bearings are going. Can I pull the valley cover to see if the cam bearings are where they should be?
ever since i got my new 383 ive been dealing with low oil pressure too..changed out 4 pumps, orings, guagues, everything.. my problem was that when i got the motor the plug wasnt in that goes in the block behind the oil pump... changed that but a wrong size one n got 80 lbs then the plug popped out n put the correct plug in and having the same issue...so hopefully its not bearings n my oil pump is just bad even tho its brand new with 1000 miles... hope you solve your problem.. check that plug tho! and feeler gauge around the crank
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How did you mount the o-ring?
It should sit on the outer metal flare (toward the opening) of the pickup tube....NOT all the way on (between the pickup tube flange & metal flare).
Thicker oil is compensation for wider tolerances. Did you verify your bearing clearances beforehand?
It should sit on the outer metal flare (toward the opening) of the pickup tube....NOT all the way on (between the pickup tube flange & metal flare).
Thicker oil is compensation for wider tolerances. Did you verify your bearing clearances beforehand?
No, I called the shop that assemlbed the bottom end to see what they were and he said he'd get back to me. I need to call him back. I wish I did it all myself now.
The o-ring is where it should be. I swapped on my stock pump and didnt change much so it's not the melling pump. I got 20w-50 to see what that does and if it holds a constant higher pressure.
The o-ring is where it should be. I swapped on my stock pump and didnt change much so it's not the melling pump. I got 20w-50 to see what that does and if it holds a constant higher pressure.
try the thicker oil... i tryed so many different things with my oil pressure problem.. finnally solved it after getting my plug issue solved then retryed everything i replaced... is your oil pressure responsive when you give it gas?
So I put 20w-50 in it and ran it for a minute or 2 until it got hot enough where I had to turn the car off. Still started at 40 cold and dropped to 20 hot idle. I may put the trans on and drive it some to see if it holds. The odd thing is now my low oil light is on when I have plenty of oil in the car. How does the oil light work? Is there a float? Why would the light be on now?
