Oil pressure dropping

[Musicars]

Try a new filter first just in case. It seems odd that you just put a cheap filter on 3 weeks prior. You don't need to drain the oil to do it so that's a super cheap experiment. Yes cheap filters have caused low oil pressure. I dropped the pan in my Denali by pulling the bolts for the front diff and forcing it down as I pulled the pan. It fits barely but it's not too bad. When installing the pan, use new pop rivets that hold the gasket in place so it doesn't slip.

I figured I would do the oil filter first as it is easy, quick, and cheap. I had never even heard of a collapsing filter until this. I only used this filter because it came with a Mobil 1 synthetic oil and filter deal. I won't be that lucky but will start there and move on up the list. I will let you know how it goes.

 

[David Smith]

Goes without saying, but while you're in there for the o ring, put a new pan gasket on too. Did mine on my 04 2wd last weekend. My oil pressure was fine but did the o ring while I was doing the gasket to fix a leak. Was surprised to see my overall pressures go up 5-8 PSI over the entire rpm range....even though I barely showed under 40 at any time before the new o ring.

I did put on a new pan gasket. You're right, it should go without saying. The old, factory gasket is riveted in, so you will have to remove the old rivets. They just tap out with a hammer and a punch. Be careful not to break the pan though!

 

[Rocket Man]

I did put on a new pan gasket. You're right, it should go without saying. The old, factory gasket is riveted in, so you will have to remove the old rivets. They just tap out with a hammer and a punch. Be careful not to break the pan though!

Use an 1/8" drill bit. No tapping necessary and that's the correct size hole to install the new rivet which is an 1/8" x 1/4" pop rivet. Don't use a bigger bit or the new rivet won't grab.

 

[Musicars]

Did the filter and replaced the sensor. Those did nothing so I am dropping the pan and seeing what I have inside. I wouldn't be surprised to find the pickup stuffed full of sludge. When I took off the filter I found the oil was already black after only a few hundred miles.

When I first got this truck it was low on oil so I figured I would find a leak or maybe it was burning oil. But after I did the first oil change I didn't lose more than a few drops as the result of old hoses. So, I figure the previous owner was not big on oil changes. The oil is still very dark after two changes. I'll see what I find in the pan.

Thanks for the tips so far.

 

[Musicars]

I dropped the pan which was much easier than expected. Didn't have to drop the axle more than 2 to 3 inches.
I was hoping that when I removed the oil pickup screen assembly nuts/bolts the o-ring would be so bad the screen would just fall out. Not so, I still had to wiggle it out. The o-ring fits pretty loose on the tube and loose in the pump hole, but will stay up there, so I am guessing it is still bad, but is it bad enough to lose all the oil pressure?
Also, for as black as the oil was I expected to find a half inch of sludge in the pan. I don't think it looked too bad. I did find some odd small pieces of metal in the pan. Some looked like solder balls. I'm going to see what is iron, what is aluminum, save them, and take some picture after I clean them up.

 

[Rocket Man]

That o-ring doesn't look too bad so I'm thinking it's probably not the problem. The ones I've seen that were causing low pressure were dry rotted or hard as a rock. Possibly the pump. How many miles are on it?

 

[Musicars]

That o-ring doesn't look too bad so I'm thinking it's probably not the problem. The ones I've seen that were causing low pressure were dry rotted or hard as a rock. Possibly the pump. How many miles are on it?

About 170,000. That's assuming it's the original engine.

 

[Musicars]

I measured a new o-ring versus the old one. Outside diameter is .13 mm wider on a new one and the inside diameter is a full 1.79 mm smaller. So, it fits a lot tighter on the tube but I don't know that the difference could cause the oil pressure to drop to nothing.

 

[Rocket Man]

I measured a new o-ring versus the old one. Outside diameter is .13 mm wider on a new one and the inside diameter is a full 1.79 mm smaller. So, it fits a lot tighter on the tube but I don't know that the difference could cause the oil pressure to drop to nothing.

Make sure you use the right one, there's 2 sizes according to the instructions that came with my pump.

 

[swathdiver]

Right, they are not interchangeable! PN# 12584922 for yours.

https://www.briantooleyracing.com/chevrolet-performance-oil-pickup-tube-o-ring-12584922.html