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Performed the autopsy on the oil pump.

CAUTION: THE FOLLOWING PROGRAM CONTAINS IMAGES THAT MAY NOT BE SUITABLE FOR SOME VIEWERS. VIEWER DISCRETION IS ADVISED.

Dropped the sump, and found some steel chips/shavings along with 5mm or so of normal sludge. Probably the remains of the distributor drive tang.

Oil pump screen intact and in place. No reason to suspect debris got INTO the pump to cause the issue.

Relief valve in place, in closed position (as it should be) and free to move.

Pump was seized when installed, freed up (but tight) on the bench. On opening, the driven gear had cracked in two. Four of the seven gear teeth had damage to the lower third of the tooth, with a fair amout of missing metal and "grooves" like grinding. One tooth has a chip. Looks like all four teeth rubbed on something. No idea why only four random teeth copped all the damage, would have expected all of them to.

No damage at all to drive gear or casing. Some marks (like machining marks) in the casing, but exactly like the half dozen or so other pumps I have pulled down and rebuilt over time. Weird that there is teeth grinding/rubbing damage but nothing on the casing. No debris in the pump at all. Debris could have gone out the pump discharge into places I don't want to think about.

Hypothesis a): one of the driven gear teeth dropped a chip. No idea why, but pump screen suggests the debris came from inside the pump. The chip rubbed on four of the teeth, wore them and finally jammed. The shock load was enough to crack the driven gear in two, and snap the distributor drive tang.

Hypothesis b): the driven gear split in two for unknown reasons. Hard to imagine, as this vehicle doesn't get leaned on. The cracked gear remained mostly where it should (my mind struggles with this too), but moved outwards enough to rub four teeth. The misalignment was enough to finally jam, and snap the distributor drive tang.

In any case, the pump gears are royally shagged. Casing is probably recoverable. I have some spare pumps with new pump gear sets in them so all good so far.

Turning the motor over by hand I can hear a squeaking noise on some parts of the revolution... suspect I have offended a bearing (not suprising... that debris had to go somewhere). Not sure I could bolt this back together and sell it in good faith. Plan is to use the short motor that the Repco head came on, and the head-and-bits of Grace's motor to get the ute mobile again.


Cheers,
Harv

That is weird - and no doubt intensely frustrating ............




does the fracture line on the gear indicate if it all let go at once or does it appear to have had a crack in it for some time that finally cried enough ?

The fractures on the gear are uniform all the way across, suggesting it let go all at once. Typical cast fracture surface. Sometimes if something cracks, holds out for a while then lets go you can see corrosion in the initial crack. No corrosion here, but then again it was living in a bath of oil. I could look to see if it has the “beach marks” you see in fatigue failure but don’t have a microscope to do it.

Could be worse, at least this happened at low load. Number One Son split an oil pump gear in an RB30 at ten bazillion rpm. That one didn’t end well…

Cheers,
Harv

This is a bugger when an engines fails !

Back in the old days, engine fail, source a donor and chuck it in, I had about 10 of them at one stage !!!!

You could always sell me the ute with no motor or gearbox, !

Greg

This used to happen to my wagon as well. No one at the time could fathom why. Daz.

EK283 wrote: Mon Mar 23, 2026 6:19 pm You could always sell me the ute with no motor or gearbox, !

It will be about a month before I throw an engine back into it. Happy to sell it as is, or put a stockish motor back in, or bolt up lightened flywheel/lumpy cam/triples/magneto/worked head if that’s what the buyer is after.

Cheers,
Harv