Low oil pressure

[rbrt43]

After the installation of the 2nd new oil pump and pickup tube, complete with new o-rings my pressure remains the same. 20psi+- at 2k rpm. <10 psi at idle. Tried parking on a significant incline at idle and nothing changed.

Since the oil pressure dropped the first time it has developed an almost inaudible knock that goes away with moderate acceleration. It doesn't smoke or indicate blowby at all so we are considering replacing all of the bearings in the bottom end of the motor.

 

[Brandon2489]

After the installation of the 2nd new oil pump and pickup tube, complete with new o-rings my pressure remains the same. 20psi+- at 2k rpm. <10 psi at idle. Tried parking on a significant incline at idle and nothing changed.

Since the oil pressure dropped the first time it has developed an almost inaudible knock that goes away with moderate acceleration. It doesn't smoke or indicate blowby at all so we are considering replacing all of the bearings in the bottom end of the motor.

Before you do all that has the oil filter been replaced with a different one yet. It was never started if it has been replaced since all this began. Just by parking on an incline won't tell you much. You have to fill it with 2 extra quarts of oil and then do that step of the process. Even then it would have to be a decent incline.

 

[Mudsport96]

I think there is a relief valve in the pan rail as well. Did you check that when the pan was off for pump replacement?

 

[Mudsport96]

 

[rbrt43]

Before you do all that has the oil filter been replaced with a different one yet. It was never started if it has been replaced since all this began. Just by parking on an incline won't tell you much. You have to fill it with 2 extra quarts of oil and then do that step of the process. Even then it would have to be a decent incline.

The oil filter and oil have been changed about 5 times since this started. Most of the filters were Fram Toughguard filters, but there was one NAPA filter and now the K&N.

 

[rbrt43]

View attachment 352026

I think there is a relief valve in the pan rail as well. Did you check that when the pan was off for pump replacement?

The mechanic said that there was a port fairly close to the drain plug, but there was nothing in it. He did say that he cleaned the pan out around it though.

 

[rbrt43]

I stand corrected. There was a relief valve in it. Since the engine has developed a knock we are going to go ahead and replace all the bearings along with that relief valve and hope that fixes the problem.

 

[Rocket Man]

I stand corrected. There was a relief valve in it. Since the engine has developed a knock we are going to go ahead and replace all the bearings along with that relief valve and hope that fixes the problem.

Which bearings?

 

[rbrt43]

Which bearings?

Rod, main, and cam bearings

 

[Rocket Man]

Rod, main, and cam bearings

So you’re doing a complete rebuild otherwise how are you going to do the cam bearings?

 

[rbrt43]

Found at least part of the problem or the results of the low oil pressure

 

[Rocket Man]

View attachment 352659Found at least part of the problem or the results of the low oil pressure

Thst looks pretty bad. What does the oil look like as well as the inside of the oil filter?

 

[rbrt43]

Mechanic said that the oil was fairly clean, this time, when he drained it. Since there is obvious wear new oil and filter are going back together.

 

[Rocket Man]

Mechanic said that the oil was fairly clean, this time, when he drained it. Since there is obvious wear new oil and filter are going back together.

Wait… I hope he’s completely rebuilding it because the cam bearings are probably shot if the mains look like that, and they can’t be replaced unless he is completely disassembling it. If they’re not replaced you still won’t get good oil pressure.

 

[rbrt43]

Yes. It's getting new cam, rod, and main bearings. One of the cam bearings had spun, but there is no damage to the cam.

 

[Rocket Man]

Good time to upgrade the cam and springs!

 

[Mudsport96]

Oh..yeah that is a problem.

 

[rbrt43]

Good time to upgrade the cam and springs!

I would like to upgrade, however, I have to have this specific vehicle for my work and it has been down for the last 6 weeks so I haven't been working, and this wasn't a planned repair.

 

[SnowBuck]

So I was able to drop my oil pan and I'm pretty sure I found the source of the low oil pressure. The pick up tube screen was completely covered with gunk. The bottom of the oil pan was full of sludge. My pick up tube o-ring seemed in pretty good shape but obviously I replaced it anyway. Cleaned the tube. Cleaned the oil pan. Pulled the plate off the bottom of the engine below the crank and cleaned that. Clearly this engine didn't have the best maintenance. Put it all back together and now my oil pressure is back up and running good.

You typed the words right off my post on a similar thread. Exact same problem: SLUDGE! Cleaned out the pan & screen...didn't need the O-ring but did it at that point. Pressure back to normal.

 

[rbrt43]

Well finally got my Tahoe back after my almost complete rebuild with a new crank and bearings all the way around. Pressure is good. Haven't driven it much but it's a little rough at idle. I've never had an engine rebuild before so I am not sure if this is common or not. Mechanic indicated it was and that it should go away after driving it for a bit.

Any input about this?

Thanks