Oil Pump breakage after replacement?? possible fix

[Gunslinger]

Hey gents, on that oil pump thing. �I bought a brand new NOS pump from Midwest Military and due to some operator issues I had to put in a new cover gasket. �I got a NOS cover gasket from MM and put it in. �It worked just fine. �When I had the motor rebuilt the rebuilder put in a Felpro cover gasket, just doing his job. �After about 3 miles the engine shut down and I had the same problem, the oil pump locked up, tore out 3 teeth, but fortunatley no problem with the cam shaft teeth. �I replaced the gasket with a new NOS gasket and that pump is fine!! �I think the problem is that the new Felpro gaskets don't give the proper .006 inch gap and then the pump locks up. �It may not be the pump but the gasket.
Todd
Maybe this should be its own post, Moderator you decide.
TG

[F Bill]

That brings up a very good point.. Has everyone with a broken Melling oil pump been checking the end clearance of your pumps? �Is it possible they have been too tight and as they heat up the clearance goes to zero and locks it up....

Todd thanks for the suggestion to split your topic off... maybe we can get to the bottom of this ..Did you find a new replacement gear to use on your pump or did you use a used one from the old pump?

[garage gnome]

When mine broke, the shaft became crooked (cracked the housing [smiley=shocked.gif]) so I can't measure it. Bill, next time you're up here, I'll have to show you that thing. It is really screwed up.

FWIW, when I put my old pump back in, I used a gasket that came with my engine rebuild kit. Whether it is the right thickness or not, I do not know.

[Gunslinger]

I miss spoke in the previous post, I had another pump on hand and had put the NOS gasket in that as well I put that in the motor and its fine.  I do want to clear something up that may have been misleading.  The NOS pump had about 400 miles on it before the rebuild, thats when the gasket was replaced and the subsequent lock up.  When I took it out I replaced it with another used pump that I had put an NOS gasket in and that is the one in the engine now.

As far as the fix goes I've got an old pump with good gears and I'm trying to get the gear off to rebuild the NOS.  Thats a tough job that I haven't figured out yet, I got one pin out but the gear won't drop off the shaft, can't get the other pin to move, so I've got to spend some time on it.

After all of that, I'm convinced that one of the big problems is the cover gear.  It was very clear when the gears broke the pump was locked up tight, we cracked the cover bolts loose and all of a suddedn the pump was free, no interference at all.

Sorry for the confusion

[Carls_jeep]

Gunslinger, was there any signs of rubbing, wear or galling in the bottom of the housing or cover? I doubt the outer rotor would expand enough to rub the sides of the housing but with the heat from the ends rubbing it may have. Was there any rubbing there?

[Gunslinger]

You know Carl thats hard to say, I've looked at several of these and it always seems that there is a wear pattern on the cover.  I did not mike out the Felpro gasket and that should be done.  I do know that when I compared them with my uncalibrated digits, it seemed that the felpro was less substantial and thinner.  The real kicker for me was wehn we cracked the cover bolts loose less than a 1/4 turn, the darn pump just freed right up.  I think its the gasket.

[rocketeer]

Now that's interesting. You may have found the answer but what bothers me is why, where brand new pumps are breaking, wasn't this found by the mfg? Did they originally check all the tolerances with one gasket and then start using a thinner one during manufacturing without rechecking those tolerances? That's unprofessional to say the least.

Larry