Beejis60

iTrader: (1)

So I have a decimated oil pump. It looks like the gerotor decided to move forward and backward into the front cover and body and chew them apart. I thought the crank endplay might have been the problem, but it's well within spec. I'm extremely certain no foreign objects got into the oil/oil pump. Anyone have any thoughts?

Gunslinger09

Unless there were excessive miles on the motor I would say it would have to be FOD. But since you say you have ruled that out it I'm going to guess just a general part failure. Sometimes **** will just go bad.

Beejis60

iTrader: (1)

Brand new motor; zero miles, zero run time at idle. It's not a 'sometimes **** goes bad' scenario. There's a reason for it.

CAMSTER

iTrader: (10)

Something was wrong for an outcome like that, not sure whether is a double roller or not but the LS oil pump must be centered on the crank with filler gage all four sides the same before is tighten up so the pump is not destroyed by the gyrator attacking one side of the pump internal.

I always open the new oil pumps to inspect inside and clean up overcasting and porting for extra flow but especially the relieve valve area overcasting comes extra heavy and dangerously stuffed, play all my tricks use synthetic oil for is internal lubricant but the point is, I know is going to do what I spec it to (NO surprises)

Beejis60

iTrader: (1)

It was installed correctly. The pump was fine before install as I also took it apart. The gerotor was fine. No casting burrs, no cracks, nothing. The inlet is fine, the spring was fine, the valve was fine and moved freely in the valve "chamber". Everything was done properly to the T. Yes, even synthetic oil, though that doesn't matter in this case.

Anthony Phillips

and now are there any broken pieces in the pump??? as stated something was wrong wrong no doubt..... maybe post pics of the damage?

Beejis60

iTrader: (1)

Well, it was eating away at the cover and body, so essentially there are miniscule shards of aluminum and steel, but no major pieces of steel, iron, aluminum, etc. Oil analysis from the motor vs. the standard confirms that of fresh oil so nothing caustic or acidic or unusual is in there that may be eating at the surfaces...

Yes, it was installed correctly, as aforementioned. Yes, assembly lube. The empirical evidence says it should be working other than the oil pressure drop, which prompted the teardown. Every single engineer I know and have questioned have come to the same conclusion, including a few GM engineers and that being "I don't know".

RezinTexas

got any pics?

BriancWS6

iTrader: (18)

You haven't mentioned what pump this is.

VTC_WS6

iTrader: (9)

Pics would be helpful. Did the gerotor fracture/shatter at all? Did the drive sleeve on the crank snout move? How many miles did that pump accumulate?

Beejis60

iTrader: (1)

Pics really aren't needed... The cover is chewed up where the gerotor rotates. The body is chewed up also where the gerotor rotates.

stock

It was centered and installed properly as aforementioned.

Drive sleeve is fine and also within spec according to the dial indicator. Outer gerotor is chewed up too where it was also chewing on the cover and body somehow. The pump now probably has one mile on it, give or take; it failed on engine dyno at 2k while slowly increasing revs. Pump was filled with oil and primed properly before starting the engine.
Again, everything was brand new from oil pan to intake to injectors and everything in between, not used or remanufactured. All oem fasteners were replaced with either ARP or A1 fasteners. Oil analysis shows the oil is fine. End play in the crank is less than half of OEM-spec. Drive sleeve is fine. Gerotor was fine prior to install. Housing casting was fine. The bypass moved freely in the sort of chamber. Intake tube is fine. All torques were fine. In fact, all tools used for measurements, like torques, weights, and 'distance' measurements were doublechecked with a different brand of the same tool at time of teardown just in case and all match my blueprint log.

I guess I'm just looking for any crazy thoughts as myself and everyone I know has zero clue what happened.

Quick Carl

Check that the damper hub clears the oil pump cover where it goes in and contacts the oil pump drive hub. On a few rare occasions I have had to turn the hub to clear.

Beejis60

iTrader: (1)

So you're saying the hub can sort of butt up against the pump cover causing it to perhaps compress a little bit? That might be the issue as that's probably the only thing no one has thought of or suggested, but there's no grinding on the cover unless the hub pushed the drive spline rearward. I know I didn't check that clearance; I've built many non-LS motors without ever checking for/blueprinting that. I cannot say if my partner checked it either nor is that in my specs for blueprinting. Everything has been torn down, cleaned and inspected so it cannot be checked now...
I will ask the GM engineer friends to see if they've experienced this in the past; if so, I'm gonna smack them for not suggesting it earlier. Thanks though.

Quick Carl

If the balancer or oil pump is aftermarket the GM guys wouldn't have the spec's for that, but something to watch out for.

Beejis60

iTrader: (1)

That's a good point.
Pump is an oem unit but the damper is not. Should be rebuilding in the next few days but can't get to the dyno until this weekend, at the earliest.