Low idle oil pressure

buddyo · April 11, 2020

Bought the truck about 10 months ago. Noticed on test drive oil pressure was low (8psi) at around 600-700 rpm. Nice truck, no engine noise and drove like new. 70 miles to home,no problem. Put a manual gage in place of sensor and confirmed the low pressure reading. Got a low pressure warning on message center and replaced the oil with 10w40 synthetic to eliminate that. But pressure didn’t improve much. Maybe enough to silence the alarm. Had the pump replaced and the oring at pickup tube also but nothing changed. I am beginning to wonder if this guy, who was suggested to me by my son actually did all the work correctly. Like i said the engine makes no noise indicating excessive bearing wear. I’m thinking about dropping the oil pan and checking the oring.The only reason I didn’t do it myself was because I don’t have a lift and space is tight but I’ll work around that. One guy here suggested to another to overfill the engine with oil and place rearend higher than the front enough to cover the oring. Anyone ever done this? Oh and the engine has 186000 miles on it.

SierraHD17 · April 11, 2020

What year and if it's an 07... what body style? 5.3? If its the 04 you have in your profile it sounds like the bypass spring is sticking in the oil pump or you have a spun cam bearing or something allowing the pressure loss downstream.

Overfilling with oil would only account for a suction leak on the o ring... if the bypass is open on the oil pump overfilling wouldn't do anything for you.

Edited April 11, 2020 by SierraHD17

buddyo · April 11, 2020

It’s an 04 Z71.Putting in a new oil pump and o-ring didn’t change anything, if in fact it was done. I didn’t know the guy. Would a spun camshaft bearing not affect the engine performance and sound?. It is a quite and smooth running machine.

tlaw91 · April 12, 2020

New used engine is like $600 while it’s apart reseal it and put new pump in yourself you’ll be like $1300 into it if you do it yourself.

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SierraHD17 · April 12, 2020

Even a brand new pump can have bypass spring issues... also coupled with the fact your first post has its doubts the guy changed out the pump. If he swapped it without removal of the pan it means full disassembly of the oil pump to install it so who knows what he did.

If you are of course verifying this issue (now) still with a test gauge. Usually a spun cam bearing makes noise but not always which is why I mention it.