[Casper the friendly G]

Originally Posted by ctrlz

At about the 26 minute mark in this video he shows the place where the pump cracks.
The part that cracks is called the stator. the rotor holds the vanes.


Also, a video explaining the destructive force of cavitation in a rotary vane pump;

Cavitation sucks!🧟

[gpskinzhut]

Originally Posted by Mark R

Here is a pic of where the LT-4 pump breaks. I replaced my ZL-1 oil pump at 14,000 miles with the Katech unit; the oil pump was still working. Katech claims they use superior material.

Yep, same failure here.

[ctrlz]

Below is the description of the system from the repair manual. The system defaults to the high flow mode (control solenoid NOT energized). The low flow mode is to reduce engine load and increase fuel economy.
Cavitation occurs when a pump is starved on the inlet side. Vacuum pockets form within the pump. When those pockets (sometimes called "bubbles") collapse, you get noise and vibration. That can be very destructive.
The LT4 does have some added drainback capacity compared to the LT1. So I presume that is there for a reason. Not sure that would explain why the LT4 is more prone to pump failure compared to LT1.

Variable Flow Oil Pump Assembly
The oil pump assembly is located within the oil pan. The oil pump assembly is fastened directly to the
rear of the balancer shaft assembly and is driven by the rotation of the balance shaft spline.
The oil pump assembly possesses variable flow capability which is made possible by a shift of the
circular vane arrangement and the actuation of an oil control valve assembly guided by the ECM. The
variable flow capability of the pump optimizes oil flow to the engine components when needed. During
performance maneuvers and acceleration the oil pump operates in a steady high pressure state.
However, during steady low load touring speeds on level terrain the oil pump operates in a steady low
pressure state.
The ECM guided "on" and "off" actuation of the oil control valve assembly allows the chamber to be
pressurized which takes the switch from high to low pressure mode. The high pressure state of the
chamber compressing the spring and shifting the center of the circular vane arrangement nearer to that
of the balancer drive shaft, decreasing the difference of the volume of oil contained between each vane.
It is this small variation in volume which produces the steady low pressure flow. It is in this mode that the
pump behaves as a smaller pump.
Advantages of variable flow oil pumping modes:
The high performance steady pressure mode is where engine temperatures and friction are
reduced because the pump only delivers the oil that the engine requires.
The low load touring steady pressure mode is where the volume of oil flow is reduced to even more
efficient levels when engine requirements allow. This efficiency reduces the resistance on
reciprocating component, allowing engine revolutions with less power resulting in fuel economy
savings.

[N Camarolina]

Thanks for this. Very interesting. I was under the impression that the transition from low flow to high flow wasn't until around 5700 RPM, but the below explanation makes it sound like the transition would happen much earlier than this and also not just driven by rpm, but perhaps other conditions that qualify as "performance maneuvers" or I guess anything that isn't simply low rpm and level terrain (low flow mode sounds like the exception rather than the rule).

I wonder if the pump is more prone to cavitation when it is in the "high flow" mode. It would be trying to suck more oil in from the pan during "high flow" so would also seem to be a higher risk for having those intake flow needs not met if the oil happens to be sloshing around too much in the oil pan (under high lateral G loads) or maybe while driving up hill under high RMP.

Originally Posted by ctrlz

Below is the description of the system from the repair manual. The system defaults to the high flow mode (control solenoid NOT energized). The low flow mode is to reduce engine load and increase fuel economy.
Cavitation occurs when a pump is starved on the inlet side. Vacuum pockets form within the pump. When those pockets (sometimes called "bubbles") collapse, you get noise and vibration. That can be very destructive.
The LT4 does have some added drainback capacity compared to the LT1. So I presume that is there for a reason. Not sure that would explain why the LT4 is more prone to pump failure compared to LT1.

Variable Flow Oil Pump Assembly
The oil pump assembly is located within the oil pan. The oil pump assembly is fastened directly to the
rear of the balancer shaft assembly and is driven by the rotation of the balance shaft spline.
The oil pump assembly possesses variable flow capability which is made possible by a shift of the
circular vane arrangement and the actuation of an oil control valve assembly guided by the ECM. The
variable flow capability of the pump optimizes oil flow to the engine components when needed. During
performance maneuvers and acceleration the oil pump operates in a steady high pressure state.
However, during steady low load touring speeds on level terrain the oil pump operates in a steady low
pressure state.
The ECM guided "on" and "off" actuation of the oil control valve assembly allows the chamber to be
pressurized which takes the switch from high to low pressure mode. The high pressure state of the
chamber compressing the spring and shifting the center of the circular vane arrangement nearer to that
of the balancer drive shaft, decreasing the difference of the volume of oil contained between each vane.
It is this small variation in volume which produces the steady low pressure flow. It is in this mode that the
pump behaves as a smaller pump.
Advantages of variable flow oil pumping modes:
The high performance steady pressure mode is where engine temperatures and friction are
reduced because the pump only delivers the oil that the engine requires.
The low load touring steady pressure mode is where the volume of oil flow is reduced to even more
efficient levels when engine requirements allow. This efficiency reduces the resistance on
reciprocating component, allowing engine revolutions with less power resulting in fuel economy
savings.

[N Camarolina]

I checked my PDR data from track driving and can confirm that the pump does not seem to behave the way that CTRLZ's excerpt from the repair manual describes. When the engine RPM crosses approx 5800 RPM, oil pressure is suddenly boosted by ~ 10 PSI, which takes it from the 40's to the mid 50s. If throttle is held above 5800, oil pressure remains in the 50s, but if it drops back below, then pressure quickly drops back into the 40s.

It appears that the high flow mode is trigged at 5800 rpm, which would imply the low flow mode is at work primarily below this rpm. I'm on my second engine, and both engines/pumps seem to work this way.

[ctrlz]

Originally Posted by N Camarolina

the pump does not seem to behave the way that CTRLZ's excerpt from the repair manual describes. When the engine RPM crosses approx 5800 RPM, oil pressure is suddenly boosted by ~ 10 PSI, which takes it from the 40's to the mid 50s. If throttle is held above 5800, oil pressure remains in the 50s, but if it drops back below, then pressure quickly drops back into the 40s.

It appears that the high flow mode is trigged at 5800 rpm, which would imply the low flow mode is at work primarily below this rpm. I'm on my second engine, and both engines/pumps seem to work this way.

This is a mysterious problem. It is quite possible GM adjusted the trigger point for the low to high shift to save the pump from damage. Certainly easier than redesigning the pump.
Also interesting that this is so much more common in the LT4, which does have oil passage differences compared to LT1.
Still very hard to imagine "starvation" with a 10 qt oil pan unless there is some crazy maneuvering at high rpm. So does this happen more often in tracked ZL1's compared to non-tracked?

[N Camarolina]

Originally Posted by ctrlz

This is a mysterious problem. It is quite possible GM adjusted the trigger point for the low to high shift to save the pump from damage. Certainly easier than redesigning the pump.
Also interesting that this is so much more common in the LT4, which does have oil passage differences compared to LT1.
Still very hard to imagine "starvation" with a 10 qt oil pan unless there is some crazy maneuvering at high rpm. So does this happen more often in tracked ZL1's compared to non-tracked?

Well, I've been hearing anecdotal evidence that's making me suspect that ENGINE FAILURE is more common in tracked G6s. But rather than being an oiling problem it could merely be because tracking (effectively sustained high RPMs and high G loads) puts more abuse on engine than street driving. Of course there are also members here who have tracked 3 times as many days as me and haven't had an engine failure yet.

The theory about GM having changed the trigger point on the pump is interesting, as it would explain why my PDR observations are at odds with your repair manual text.

I'd love to compare my 21 SS 1LE PDR data (oil pump pressures vs RPM) to PDR data from a 2017 or 2018 SS 1LE. Does anyone have a raw PDR track recording they'd like to share with me so that I can compare them on PI Toolbox? Perferably on a track with some longer straightways so I can see some high rpms at low lateral G loads?

[Ryfly05]

How do you get oil pressure data from the PDR? What other info can you extract from it? I've got a couple PDR track sessions on my 22 SS 1LE, I'd like to see that info.

[ctrlz]

At the risk of starting a Holy War, I wonder if anyone running 5W-30 (exclusively) has had a pump failure. The recommended 40 weight oil is going to be more prone to cavitation than a 30 weight.

As an aside, my digging seems to indicate our oil pump was originally developed for the Chevy Cruze. The "economy" (i.e. low volume) mode is supposedly good for ~3% in that car.

[Mark R]

Originally Posted by N Camarolina

Well, I've been hearing anecdotal evidence that's making me suspect that ENGINE FAILURE is more common in tracked G6s. But rather than being an oiling problem it could merely be because tracking (effectively sustained high RPMs and high G loads) puts more abuse on engine than street driving. Of course there are also members here who have tracked 3 times as many days as me and haven't had an engine failure yet.

The theory about GM having changed the trigger point on the pump is interesting, as it would explain why my PDR observations are at odds with your repair manual text.

I'd love to compare my 21 SS 1LE PDR data (oil pump pressures vs RPM) to PDR data from a 2017 or 2018 SS 1LE. Does anyone have a raw PDR track recording they'd like to share with me so that I can compare them on PI Toolbox? Perferably on a track with some longer straightways so I can see some high rpms at low lateral G loads?

I follow the oil pump thread in the ZL-1 forum. Most failures are at about 14,000 miles, not on the track but on the street or sometimes in parking lots, 2017-2018 mostly, but creeping into later years.

My theory is that stupid cut in the inner ring is an obvious weak point. It doesn't surprise me that it breaks there. Katech says theirs don't break because they use stronger material for that inner ring. If that's all it takes to solve the problem, it does not need to be over thought.

I replaced my 2018 pump at 14,000 miles with the Katech unit before the stock pump had a chance to ruin my ownership experience.

[N Camarolina]

Originally Posted by Mark R

I follow the oil pump thread in the ZL-1 forum. Most failures are at about 14,000 miles, not on the track but on the street or sometimes in parking lots, 2017-2018 mostly, but creeping into later years.

My theory is that stupid cut in the inner ring is an obvious weak point. It doesn't surprise me that it breaks there. Katech says theirs don't break because they use stronger material for that inner ring. If that's all it takes to solve the problem, it does not need to be over thought.

I replaced my 2018 pump at 14,000 miles with the Katech unit before the stock pump had a chance to ruin my ownership experience.

So you've employed an interesting strategy. Forgo your engine warrantee by replacing the pump with something that you hope/expect is better. If you have an engine failure now, it hopefully won't be caused by pump problem, but GM will have the perfect excuse to say that your Katek pump could have caused the failure of the engine.

[Mark R]

Originally Posted by N Camarolina

So you've employed an interesting strategy. Forgo your engine warrantee by replacing the pump with something that you hope/expect is better. If you have an engine failure now, it hopefully won't be caused by pump problem, but GM will have the perfect excuse to say that your Katek pump could have caused the failure of the engine.

The only failure I was concerned about was oil pump failure. Not any more

[Puddin]

2016 2SS bought new lost oil pump at 9k miles and trashed the bottom end with it. Happened while data logging for Pray.

[articblueSS]

My 2018 SS was just diagnosed yesterday with an oil pump failure. The car has just over 20k miles on it. The only symptom i had was a strange humming/buzzing noise from the front of the engine that would change pitch with the rpms. I never lost oil pressure tho. GM is replacing the pump under my power train warranty.