Cat 310 plunger cracks?

[Legacycarwash]

Good evening everyone. So I’m resealing some older cat 310’s and when I look at some of the plungers I see what appears to be cracks but yet they are completely smooth. Won’t catch a finger nail or anything. Only visible. Seems like if they were true cracks you could feel them. So I’m hoping someone with more experience can clue me in so I know what I need to do. Thanks in advance!

 

[MEP001]

You need to replace it. Odds are really good that water is getting through the cracks, and it will eventually rust out the piston rod or get into the crankcase. You must also replace the o-ring, the backup ring, and the copper washer on the bolt. They are not intended to be tightened more than once.

 

[Legacycarwash]

You need to replace it. Odds are really good that water is getting through the cracks, and it will eventually rust out the piston rod or get into the crankcase. You must also replace the o-ring, the backup ring, and the copper washer on the bolt. They are not intended to be tightened more than once.

Thank you the advice sir! ill go thru all my old pumps and see how many I can salvage.

 

[ShinePro]

MEP is 100% correct.
But
new plungers are $90.00 a piece
A new entire pump is only $711.
Put your seals in run it til she quits and buy a new one.

 

[MEP001]

If he's only got one broken plunger, it's worth $90 to replace.

 

[Legacycarwash]

Yea. Two are like that. But I have a stash of old pumps from the previous owner. I think 8-10 laying around. So time to make one pile of them and sort out what’s salvageable. Man. The old guy who owned it never threw anything away!