I have about 9k on my built motor, everything was replaced with new parts and I also installed a topline oil pump. Im running an oil cooler from a sandwhich adapter at the oil filter. Naturally the oil pressure dropped a little after that but was still plenty with the stock motor.

Now when I installed this new motor I noticed the oil pressure was only around 40psi cruising after the car warmed up. About 10-15psi lower than before but seemed fine. Still around 20psi at idle so I didn't think anything of it. The problem is that when the car gets really hot on a really hot day the idle pressure will sit around 10-15psi and occationally it will just drop go less than 5psi. Like the gauge almost bottoms out and just bounces around there for a little while. When I see this I cut the car off right away, when I crank it back up it goes back to normal.

It only does when idleing for a few minutes. This happened 2-3 times last week on a hot day but since then its been cooler and hasn't done it anymore. Im about to pull the head to replace the headgasket so Im wondering what I can check while im in there. I dont want this motor to spin a bearing from a bad oil pump. Has anyone seen anything like this?

Yep, sounds like mine did and it was due to a spun #1 rod bearing. If I were you I would pull the oil pan and inspect stuff down there.

There is no way the car has a spun bearing. It has been driven many times since that happened and no noise or anything coming from the motor. It did this last summer a little also but never tried to figure out what was wrong.

Mechanical or Electronic oil pressure gauge? I run an Autometer Cobalt electric version, but would rather have the mechanical. Anyway a few members have had an issue or two with Autometer's electrical sensors. What I heard, they replace them without question, but still could be your issue??

Cobalt full sweep electric gauge. I actually have another sensor in the house. I may try that. Its not that hard to replace.

my mechanical reads exactly what he's experiencing. You're fine during warmer temps. zac experienced something radically different.

Originally posted by 420agreenvilleSC
my mechanical reads exactly what he's experiencing. You're fine during warmer temps. zac experienced something radically different.

So you get lower oil pressure during hot summers also?

exactly. as long as it rises w/ RPMs up to 35 or over, you're fine. 35 is a little low though for rpms. maybe over 40. can't remember. car's been in the garage since september

The reason pressure drops when it gets hot is because the oil is actually getting hotter and thinner, thats why most people run thicker oil in the summer and thinner in the winter. This happend to me and a few days later I was towing it home. It could be your sending unit, is it remote mounted or mounted on the back of the block?

Oil pressure sensor is on the back of the block. It has been there for almost 3 years with no problems.

wouldn't worry about it. depending on your summer/winter temps, I do as follows:

Summer: 10w40
winter: 10w30

lowest average winter temps: high 20's
highest average summer temps: high 80's

I agree with changing oil weigh to see if there is an improvement.

Does the vehicle use alot of oil? (or lose alot of oil)