Sudden oil press loss at startup
Sudden oil press loss at startup At lunch today in my work truck (03 lq4, 185k mi) went to leave and truck had no, to maybe 2psi at startup. Hard to say how accurate gauge is on the far end.
Immediately turned truck back off and checked the basics. Ok, level checks good, color/smell is good, it was only 2k miles since last change.
Last oil change I did replace a bad sender, so I think great the china sender failed already, and restarted truck and let it idle for about 20sec. No dice, lifter tapping now, so it really is low psi.
I gave the throttle a small bump and the psi went up and right to normal range. Took about a block or so of driving and the lifter quit tapping too.
went ahead and stopped at auto parts store along the way and picked up a new filter. Thinking possibly filter collapsed, clogged, or drain back failed, not sure.
truck did the whole no psi bit again, but this time I was quicker on the gas and got the psi up right after starting.
At no point for the rest of my trip did the oil psi look anywhere out of every day range. Idle, cruise, accelerating, all normal ranges.
Now last oil change I also did some preventative maintenance and replaced the pan gasket that was seeping. While inside I also did a mahle pickup oring and added a filter bypass delete.
I’ll replace the filter in the parking lot before leaving today, and see if that fixes it. I’m not thinking it’s the oring at the moment because it’s new, and if it was bad, it would most likely be bad immediately and not 2k mi old.
Immediately turned truck back off and checked the basics. Ok, level checks good, color/smell is good, it was only 2k miles since last change.
Last oil change I did replace a bad sender, so I think great the china sender failed already, and restarted truck and let it idle for about 20sec. No dice, lifter tapping now, so it really is low psi.
I gave the throttle a small bump and the psi went up and right to normal range. Took about a block or so of driving and the lifter quit tapping too.
went ahead and stopped at auto parts store along the way and picked up a new filter. Thinking possibly filter collapsed, clogged, or drain back failed, not sure.
truck did the whole no psi bit again, but this time I was quicker on the gas and got the psi up right after starting.
At no point for the rest of my trip did the oil psi look anywhere out of every day range. Idle, cruise, accelerating, all normal ranges.
Now last oil change I also did some preventative maintenance and replaced the pan gasket that was seeping. While inside I also did a mahle pickup oring and added a filter bypass delete.
I’ll replace the filter in the parking lot before leaving today, and see if that fixes it. I’m not thinking it’s the oring at the moment because it’s new, and if it was bad, it would most likely be bad immediately and not 2k mi old.
So far a filter has done the trick. Obviously I’ll be keeping a close eye on the gauge for a while.
im going to open up the old filter tonight and see if there is anything out of place.
im going to open up the old filter tonight and see if there is anything out of place.
Two things.
First, there is a strainer on the OPS that gets clogged, easy fix if that's it. But my symptoms of this problem were pressure at startup and eventually pressure would drop over the period of a few minutes. Opposite of what you're seeing.
Secondly, not common but there is a check valve in the oil pump that can stick with even the slightest grit in the oil. Mine stuck in a position where low flow was no PSI at startup but a rev would let it build pressure by eventually overcoming the gap.
The oil encounters this valve pre-filter. If you have no grit in your filter this may not be your problem, but sure sounds like my symptoms I had.
Pic of it here with some tinkering I did with it:
https://ls1tech.com/forums/generatio...l#post20118172
First, there is a strainer on the OPS that gets clogged, easy fix if that's it. But my symptoms of this problem were pressure at startup and eventually pressure would drop over the period of a few minutes. Opposite of what you're seeing.
Secondly, not common but there is a check valve in the oil pump that can stick with even the slightest grit in the oil. Mine stuck in a position where low flow was no PSI at startup but a rev would let it build pressure by eventually overcoming the gap.
The oil encounters this valve pre-filter. If you have no grit in your filter this may not be your problem, but sure sounds like my symptoms I had.
Pic of it here with some tinkering I did with it:
https://ls1tech.com/forums/generatio...l#post20118172
Last edited by mk3cn4; Apr 5, 2024 at 08:30 AM.
