[Les7311]

Originally Posted by Les7311

Mechanic did checks and tests, all else tested well.

They buttoning up and ready by Monday.

So more things discovered..... still on the lift.

[Dixie ZL1]

Just heard from the tech and fortunately the pump stayed together in mine. Still a catastrophic failure, but no metal in the pan.

He pulled two rod caps and the bearings look great. Plan to change the oil again at 500 miles and will send a sample out for analysis.

Expect to Have it back next Monday. My dealership and tech are awesome and I couldn’t be happier with them.

[IneedAZ]

may have missed it, but is there an alternative pump available or only the same ones that are having issue.

[dbb143]

Lucky you. Friday will be 5 weeks for mine and now tee tech isn't confident he'll have it done before next week. Didn't inspire any confidence in the job getting done correctly when the tech told me today it was taking longer than he thought because he had to refigure out where all the lines go because he can't remember!!!!! OMFG I'm about to go postal!

[dbb143]

Originally Posted by IneedAZ

may have missed it, but is there an alternative pump available or only the same ones that are having issue.

It seems/ sounds like it was a bad batch of pumps/parts

[collinms]

Originally Posted by dbb143

Lucky you. Friday will be 5 weeks for mine and now tee tech isn't confident he'll have it done before next week. Didn't inspire any confidence in the job getting done correctly when the tech told me today it was taking longer than he thought because he had to refigure out where all the lines go because he can't remember!!!!! OMFG I'm about to go postal!

Shouldn't take that long. I'd get upper management involved.

[Dixie ZL1]

Originally Posted by dbb143

Lucky you. Friday will be 5 weeks for mine and now tee tech isn't confident he'll have it done before next week. Didn't inspire any confidence in the job getting done correctly when the tech told me today it was taking longer than he thought because he had to refigure out where all the lines go because he can't remember!!!!! OMFG I'm about to go postal!

Sorry man. I hope they get on it soon, absolutely no excuse for this repair to take that long.

[crossroaddemons]

Originally Posted by Dixie ZL1

Sorry man. I hope they get on it soon, absolutely no excuse for this repair to take that long.

What is it that is failing in the pump? Shaft wear?

[dbb143]

Originally Posted by crossroaddemons

What is it that is failing in the pump? Shaft wear?

Mine literally exploded and threw shrapnel into the pan. Best they can figure is a bad part. Tech said he had never seen anything like that before, but my confidence in his competence is dwindling by the day . . .

[Dixie ZL1]

Originally Posted by crossroaddemons

What is it that is failing in the pump? Shaft wear?

The pump assembly is comprised of three main sections 1) outer housing that bolts to the front of the block and holds the assembly together, 2) middle section that effectively creates the housing the impeller rides inside of to create pressure and holds the pressure relief mechanism, and 3) the impeller that is keyed to the crank and creates pressure as the crank rotates within the static outer assembly bolted to the block.

What actually fails is the middle section, the interior circumference of which allows the impeller to create pressure, and also holds the pressure relief assembly.

Question is - how does the middle section break into multiple pieces in a rotating assembly if the inside and outside are circularly symmetric and concentric? I don't believe it will unless a force pulls the impeller into the middle section of the pump.

I've been thinking about this a lot and have a theory.......

The Gen V LT1 and LT4 use exactly the same pump and yet only the LT4 has experienced failure - the only difference is the blower that is also driven by the crank shaft.

My unproven theory is some engines will have a tolerance stack up issue where the crankshaft bearing clearance is on the loose end of the spec, say .004' (.002" up / down) and the oil pump impeller to inner housing clearance is less (say .001" - .0015") such that under heavy loads the crank is pulled upward by the blower pulley creating contact internal to the pump, resulting in the failure.

Its just a theory and one can also point to the quality of sintered metal
components, casting imperfections, or stress risers in the design around the alignment pins, but none of those potential causes explains why only the LT4 and not the LT1 with exactly the same pump over the same timeframes.

We might never know, but this is my guess.

[VAZL1]

Originally Posted by Dixie ZL1

The pump assembly is comprised of three main sections 1) outer housing that bolts to the front of the block and holds the assembly together, 2) middle section that effectively creates the housing the impeller rides inside of to create pressure and holds the pressure relief mechanism, and 3) the impeller that is keyed to the crank and creates pressure as the crank rotates within the static outer assembly bolted to the block.

What actually fails is the middle section, the interior circumference of which allows the impeller to create pressure, and also holds the pressure relief assembly.

Question is - how does the middle section break into multiple pieces in a rotating assembly if the inside and outside are circularly symmetric and concentric? I don't believe it will unless a force pulls the impeller into the middle section of the pump.

I've been thinking about this a lot and have a theory.......

The Gen V LT1 and LT4 use exactly the same pump and yet only the LT4 has experienced failure - the only difference is the blower that is also driven by the crank shaft.

My unproven theory is some engines will have a tolerance stack up issue where the crankshaft bearing clearance is on the loose end of the spec, say .004' (.002" up / down) and the oil pump impeller to inner housing clearance is less (say .001" - .0015") such that under heavy loads the crank is pulled upward by the blower pulley creating contact internal to the pump, resulting in the failure.

Its just a theory and one can also point to the quality of sintered metal
components, casting imperfections, or stress risers in the design around the alignment pins, but none of those potential causes explains why only the LT4 and not the LT1 with exactly the same pump over the same timeframes.

We might never know, but this is my guess.

Plausible theory. I think Katech has an upgraded one for the gen6 or at least they were working on one. Has anyone tired it? I would be interested just for piece of mind.

[IneedAZ]

Originally Posted by dbb143

It seems/ sounds like it was a bad batch of pumps/parts

Well, I am at 11k miles now on my 2017. So far it seems ok. When I get ready to do a cam change I hope an alternative pump is available.

[Boost or bust]

Hey, all: really sorry to near about all of the oil pump failures still happening. I’m also pretty annoyed and surprised that General Motors hasn’t issued a TSB about the issue it is absolutely widespread. GM has a long history of failing oil pumps ...take a look online .

I am not aware of any satisfactory aftermarket pump to replace the failing factory ones .

When my oriole pump failed last year it took the dealer three weeks to figure out what was going on and they put everything back together with a new pump even though that was metal shrapnel everywhere. they would not warrantee a new engine for me . I ended up selling the Camaro as it was the fourth GM car I owned that had catastrophic issues and I swore off GM never to own one again . I really liked my ZL one Camaro but had no intentions in having that sinking feeling that it would die on the road with me at any given time without GM acknowledging that they had a problem . I cannot live with that . It might be great for those of you that have excellent dealer relationships but the whole idea is not to have the failure in the first place and to also have a car company be straight with us about what’s going on and I could never get the truth out of them about what’s going on with our oil pumps . I still monitor the forum here and if I hear of anything new I will certainly share it good luck to everyone .

[crossroaddemons]

Originally Posted by Dixie ZL1

The pump assembly is comprised of three main sections 1) outer housing that bolts to the front of the block and holds the assembly together, 2) middle section that effectively creates the housing the impeller rides inside of to create pressure and holds the pressure relief mechanism, and 3) the impeller that is keyed to the crank and creates pressure as the crank rotates within the static outer assembly bolted to the block.

What actually fails is the middle section, the interior circumference of which allows the impeller to create pressure, and also holds the pressure relief assembly.

Question is - how does the middle section break into multiple pieces in a rotating assembly if the inside and outside are circularly symmetric and concentric? I don't believe it will unless a force pulls the impeller into the middle section of the pump.

I've been thinking about this a lot and have a theory.......

The Gen V LT1 and LT4 use exactly the same pump and yet only the LT4 has experienced failure - the only difference is the blower that is also driven by the crank shaft.

My unproven theory is some engines will have a tolerance stack up issue where the crankshaft bearing clearance is on the loose end of the spec, say .004' (.002" up / down) and the oil pump impeller to inner housing clearance is less (say .001" - .0015") such that under heavy loads the crank is pulled upward by the blower pulley creating contact internal to the pump, resulting in the failure.

Its just a theory and one can also point to the quality of sintered metal
components, casting imperfections, or stress risers in the design around the alignment pins, but none of those potential causes explains why only the LT4 and not the LT1 with exactly the same pump over the same timeframes.

We might never know, but this is my guess.

The only counter to that theory is the blower is driven by a serpentine ribbed belt which has a tensioner so the amount of perpendicular force theoretically applied to the centerline of the crank is likely insufficient to do so. Transmission of vibration under load however is entirely possible in my opinion.