LS Oil Pressure Issue

[gimpy]

I have a work truck with an LQ4 6 liter that had the oil pump fail. I had to limp back to my shop a couple miles, with virtually no oil pressure. Came to find out the cam was smoked too. Replaced cam, timing chain, lifters, pushrods, valve seals, and of course the oil pump.

Upon reassembly, startup oil pressure was reading 20 psi. Once the motor fully heated up, oil pressure dropped to 2-3 psi. Figuring I must’ve damaged the oil pickup tube o-ring during assembly, I tore it all back down, checked o-ring and replaced with another OE part and reassembled. Upon reassembly, it has exhibited the same behavior.

There’s no significant bottom end noise, but I’m assuming I have a bad rod bearing based on a light knock when the motor is gradually increasing rpm during light acceleration, and have ordered bearings as well. I had visually inspected them when I had the windage tray off and attempted to wiggle them all to verify. I’m assuming they may have been damaged from the 5-10 drive with low pressure.

Is there something I’m possibly missing? I understand the cam bearings “could” be a culprit, but have doubts about that. Any LS techs here ever experience similar problems? Motor has about 230k on it.

 

[Skunk]

If you drove it without oil pressure, the bottom end is likely smoked. Simply changing bearings won’t fix it.
Just go get yourself a long block if you want to keep the truck....

 

[BullGear]

If you drove it without oil pressure, the bottom end is likely smoked. Simply changing bearings won’t fix it.
Just go get yourself a long block if you want to keep the truck....

Agreed. Once you drove it, you doomed the entire engine. Sorry!

 

[gimpy]

It registered up to 15 psi over the couple miles. As low as 3-4. I’m really hoping it’s not trashed. No indication of spun bearings, but I’m sure they will tell the tale when I get them out.

 

[mgoodrich]

does this have the active fuel management system? (4 cylinders drop out under light load)

 

[gimpy]

does this have the active fuel management system? (4 cylinders drop out under light load)

No

 

[gimpy]

Cam was wiped out long before the pump went

 

[Expert684]

I had an old Dodge b100 van, 318 with a ton of miles and low oil pressure. I put 50wt Valvoline racing oil, had 40-60 PSI. Don’t know how long it will last? I drove the van a few more years.

 

[Edds]

I'm not familiar with that engine but have you checked the oil pump pressure relief valve to see if it is stuck open?

 

[gimpy]

I'm not familiar with that engine but have you checked the oil pump pressure relief valve to see if it is stuck open?

Yes. Disassembled the pump to check

 

[Expert684]

Bearing clearance is excessive. You might “milk” it along. But sooner than later it will crap out.

 

[346ci]

No way I'd waste time with the cam when you lost oil psi and drove it. It needs a complete tear down.

The 6.0 is sought after for swaps but you might luck up at a local junk yard.

 

[2ndamendfan]

Have you put a manual gage on it to verify oil pressure? Most of the LS engines have a screen under the oil the sending unit that gets plugged.

They also have known sending unit and gage issues.

 

[chevy_man]

New bearings throughout, grind the crank, new oil pump. Pistons and rings of course.

I'd also hot tank it, too make sure you get any old bearing material out.

While it's out get the heads decked, toss the comp trunnion kit at the rockers, new springs, and a decent cam.

 

[JMGlasgow]

I'd bet your main and rod bearings are toast.

 

[S197]

I have a work truck with an LQ4 6 liter that had the oil pump fail. I had to limp back to my shop a couple miles, with virtually no oil pressure. Came to find out the cam was smoked too. Replaced cam, timing chain, lifters, pushrods, valve seals, and of course the oil pump.

Upon reassembly, startup oil pressure was reading 20 psi. Once the motor fully heated up, oil pressure dropped to 2-3 psi. Figuring I must’ve damaged the oil pickup tube o-ring during assembly, I tore it all back down, checked o-ring and replaced with another OE part and reassembled. Upon reassembly, it has exhibited the same behavior.

There’s no significant bottom end noise, but I’m assuming I have a bad rod bearing based on a light knock when the motor is gradually increasing rpm during light acceleration, and have ordered bearings as well. I had visually inspected them when I had the windage tray off and attempted to wiggle them all to verify. I’m assuming they may have been damaged from the 5-10 drive with low pressure.

Is there something I’m possibly missing? I understand the cam bearings “could” be a culprit, but have doubts about that. Any LS techs here ever experience similar problems? Motor has about 230k on it.

Save yourself time and money and buy another LS. The best thing about an LS is they cheap and plentiful!

this is a great site for salvage cars

https://www.copart.com/

 

[gimpy]

I’m hoping to swap the bearings in the next week or so and see what happens.

 

[Gregor.Samsa]

I’d bet this little metal flakes are in all the oil galleys and passages.

 

[gimpy]

I’d bet this little metal flakes are in all the oil galleys and passages.

It’s all been flushed. Twice now

 

[camotoe]

Dump 15w 45 diesel oil in and run it.

 

[JMGlasgow]

That will only prolong the inevitable and lead to more damage.

 

[gimpy]

Added

Dump 15w 45 diesel oil in and run it.

Lucas oil at the recommendation of a friend; did nothing

 

[Skunk]

Dude, you wiped a roller camshaft. That in itself is quite an accomplishment.

Your crank is all probably all grooved up and the oil galleys in the journals are full of bearing material. I admire your optimism, but you're trying to band-aid an engine with serious problems and 250k on the odometer. Don't spend too much time and money fooling with it.

 

[2ndamendfan]

That will only prolong the inevitable and lead to more damage.

More damage than what?? By all accounts from everyone here the engine is trashed anyway.
.

 

[Jake03]

Excessive bearing clearance. You probably have cam or main bearings that are completely worn out.
Cam bearings tend to be the most common culprit.

 

[j-moose32]

As stated above the engine is trashed. Don’t waste any excessive time or money in band aid fixes. Your taking a lot apart so you clearly know what you doing. Look at that lifter and cam lobe. You know the real answer lol. Your just looking for support/ hope for a miracle... we’ve all been there lol

 

[JMGlasgow]

More damage than what?? By all accounts from everyone here the engine is trashed anyway.
.

At this point the engine is probably repairable (with some machine shop time), keep going and it won't be. It will either throw a rod, or break the crank. Both of which typically destroy the block.

 

[rjacobs]

Dude, you wiped a roller camshaft. That in itself is quite an accomplishment.

You dont know LS engines do you?

That cam/lifter failure is EXTREMELY common.

Its not so much the cam, but the lifters that are garbage. The spring fails, you lose pre-load and then it HAMMERS the cam and the results look like the picture above. I refuse to put factory lifters back in LS motors because I dont trust them. Johnsons all day long...

And as everybody else says all that debris going through that motor has likely trashed at least main bearings, but possibly also cam bearings(guessing you inspected them when you swapped the cam though). The crank MAY be ok, may not be ok.

 

[supercorndogs]

Dude, you wiped a roller camshaft. That in itself is quite an accomplishment.

Your crank is all probably all grooved up and the oil galleys in the journals are full of bearing material. I admire your optimism, but you're trying to band-aid an engine with serious problems and 250k on the odometer. Don't spend too much time and money fooling with it.

I have seen plenty of roller cams ruined.

 

[Skunk]

Not familiar with the LS at all. But, I do know an awful lot about SB2's.

I guess I'm just accustomed to more substantial parts.
Either way, that engine is done.

 

[chevy_man]

More damage than what?? By all accounts from everyone here the engine is trashed anyway.
.

Right now you have a good core that will get you $250-500 depending on location. Swap it with a junkyard pullout for $1k-1.5k and be done if you don't want to rebuild.

Or wait for the catastrophic failure that leaves you waiting on a tow without anything to sell.


If you had a cam failure someone didn't take care of it at some point. I've ran nothing but mobil 1 in my 03, and it's at 250k with no piston slap or lifter ticks. I'm waiting for it, have some ls7 lifters, springs, and a comp cam on the shelf, but it keeps on purring without complaint.

 

[rjacobs]

ls7 lifters

garbage...

but on a motor that ALREADY has 250k+ miles, I guess it would be hard to put anything more expensive in.

 

[gimpy]

Dude, you wiped a roller camshaft. That in itself is quite an accomplishment.

Your crank is all probably all grooved up and the oil galleys in the journals are full of bearing material. I admire your optimism, but you're trying to band-aid an engine with serious problems and 250k on the odometer. Don't spend too much time and money fooling with it.

Camshaft was toast long before this. It was toast long before I even bought the truck. It’s a known issue with the LS, along with oil pumps

 

[chevy_man]

garbage...

but on a motor that ALREADY has 250k+ miles, I guess it would be hard to put anything more expensive in.

Trick is you disassemble and clean them when brand new. I've been surprised how many had junk and burrs in them.

They are cheap, and couldn't justify spending big money for a mild cam without big heads and intake.

 

[Foul Mike]

I have worked in shops fixing junk and running wreckers most of my life. I have pulled many vehicles to the shop for repairs where they lost their oil pressure or were overheated or a bearing was giving out and the drivers almost all said something to the effect,"I could see the lights of that town up ahead and figured I could make it,"
I always asked them,"Was there some kind of warning like a light or bad readings on a gauge or a hot smell?"
Once in a while they would say no but a lot of them would say "Yes, but I could see the lights of the town up ahead and figured I could make it and I didn't want to stop as I am in a hurry."
Well, those lights up ahead are about 5 to 10 miles away and you are stopped now aren't you? always came to my mind.

It always made me wonder why there are those lights and gauges in the dash to warn you and why they didn't pay attention to them? Some are so stupid that they just don't know and probably shouldn't be driving with a mental capacity that is that weak, but the others? I always wondered if they felt any better about that hurry they were in and didn't want to walk, was it worth it?
They were always the ones that screamed like a mashed cat when they found out their engine, transmission, wheel bearing etc. was going to cost so much as they had totally toasted the damn thing instead of shutting it down while there was still something left to rebuild/repair.

I have had cars, trucks, tractors etc. have failures of some sort and always shut them down as soon as I was aware of a problem and hauled them in or fixed them right there instead of trying to "limp it in." Lot cheaper that way.

People never cease to amaze me how stupid they are when a light or gauge is trying it's best to tell you something is wrong but they boff it off. "Surely it will make it, it's only a few miles."

The only way I would keep on keepin on is if it were life or death.