I have 06 Denali that I drove 20 miles and things were fine. Turned it off and went inside C store. Started it up Bell is going off and I spaced it off and drove a block before realizing gauge read zero. Turned it off started again and had OP although low. No bell. Drove a mile to work and No OP since. Upper end chatter got a little louder. Hauled it home thinking it was an O-ring problem..This is a used replacement with supposedly 90K two years ago because an O-ring problem did not get caught quick enough.
Pan is off. O-ring seemed fine. Both valve covers are off. Don't see any signs of lifter problems. Took main cap 4 off and bearing looks like new. No junk in pan and pick up tube looks fine. Took oil pump off and no broken gears. I am not sure what else to look at on the pump.

I have a brand new HV295 from the problem 2 years ago.. long story. Got a new GM o-ring and I would like to put it in and get things back together. A mechanic told me he has seen high pressure pumps take mains out so now I don't know what to do. It has the spring that came in it and I don't have the optional one that it says came with it. I would buy one if possible. Am I worried about nothing or what would be your thoughts? It also looks like I need a new balancer bolt and a tool to get the main tightened correctly. I only have a torque wrench.
Thank you

 

There is a pressure bypass on the oil pump itself, If it sticks open you'll lose oil pressure.
This video will show what I am referring to.

 

I would bet that is the issue here. Pressure doesn't just drop all of a sudden UNLESS something suddenly bleeds it off.

 

Thank you .. that is something I did not know about.Will check it tomorrow . By the way a little bit ago I saw a picture of an engine you had on a test stand. That makes a guy dream big! What size is it? I am a little behind on LS stuff. All of my experience is on pre Ls stuff.

 

Also any advice on a tool to get the main cap and balancer bolt back on correctly?

Thank you

 

I assume you're talking about my engine that was on the test stand, If it's the one I think it is....It's just a extra stock 5.3 that I had. Long story short, It was a test engine so I could work out some bugs before I put everything on a 408. The only parts left stock on the 408 if the bare block, Everything else is aftermarket and I have quite a bit tied up in it and didn't want to risk hurting it by not having the bugs worked out.

The main will need to be retorqued to spec (specs are easy to look up) Put a little sealer on the small outer bolt heads so you don't have oil seep past them.

They make a tool to press on the balancer, You should be able to rent it at an auto parts store. Just make sure it threads in easily because you don't want to mess up the threads. Don't try it using just the balancer bolt, The bolt doesn't engage the threads far enough and can pull the threads out of the crankshaft.
The balancer bolt is also a one time use bolt so you'll need to get a new one at the parts store, They are less than $10.

 

DBL post

 

Thank you. I have the tool to install the balancer. Also found the torque specs. I am lost at the second step of the main cap and the angle that it needs to be tightened to. It looks like I need to find a tool ?

 

You can probably rent the tool also but if you do much work on engine you might as well buy one they aren't very expensive ($15 and up). They are easy to use, Basically you torque to spec then put the gauge on and it measures how much further you need to turn the bolt in degrees to arrive at the final point.

 

Picked up the tool shown in the video. I believe you guys named the problem( I hope)! This valve in the pump was pretty tight. Had to push a little to get it out of the housing.Was not free at all. I have put the new pump on and need to get some gaskets to get everything back together. Thank you for your help.

 

Let us know how it goes.

 

When you get it back together verify the gauge pressure with a mechanical gauge, LS oil sending units aren't exactly known for lasting forever.

 

Have 55 lbs of pressure . Also have a new problem. upper end has a noticeable chatter. It is not as loud as it was with no op , but prior to the problem it was not there.Before replacing the pump I had both vale covers off and did not find any rockers that were loose. I only let it run maybe 3-4 minutes because I had not put WP and hoses on yet today. Any suggestions?
Thank you

 

I would get everything hooked up so you can safely run it and see if it comes out of it. It could be lifters not fully pumped up. Running with low/no oil pressure will usually hurt bearings before it hurts valvetrain but anything is possible I guess. 3-4 minutes is usually long enough to quite them down though. Slight chance but part of the noise could be from running it with the block/heads empty and no water pump and sound traveling through the voids that would normally be absorbed by the water.

 

Maybe I do have some luck! Started it this morning after putting everything back together. Noise is gone. had it running several time today and everything seems as it should. Need to get a tire fixed before I can go for a drive. Thank you for your help on this. I have decided if I start to do much more with these engines I will invest in a decent wrench of some sort to do the final torque on these damn bolts. I would much prefer the old ft pound system.

 

Buy ARP and torque as usual...

 

Sorry, not following you. ARP bolts still use ft pounds and not the ft/degree system?

 

Yes. ARP bolts should be torqued in ft. lbs....at least for their headbolts anyway, and are re-usable.

 

Thank you

 

Well guys just an update.. got everything back together after this post in September. The upper noise did go away after it got everything lubricated. 60 psi at start up and ran down the highway at 50 psi all day. Made several 2hour trips to kids college football games. Then about a month ago hit a deer that was on a dead run. I was going 60 and he was going 70 less than a 1/4 mile from our driveway. We both lost!
Thank you all for your help on this.