Should i replace these pistons and rings (with pics)

blakester · Sep 22, 2019

Hey everyone, I have been trying to diagnose a poor preforming when hot, black smoke (all the time) issue with my excavator. As per the thread title im wondering if i should replace these pistons and rings. I only pulled one out of the machine, and it seems to be in good shape but i do notice wear on one side that has gone through the markings on the casting. I would assume best practice is to replace all 3 if so. The machine has roughly 3000 hours on it. I'm not sure that this is contributing to the black smoke issue, but i;m covering all my bases.

As far the black smoke, Im leaning towards the injectors / injector pump at this point. I pulled the head off and gave it a polish, the gasket looked to be in good shape, and visual inspection does not show any cracks. There was no oil in the coolant when i drained it, nor was there any coolant in the oil when i pulled the oil pan off. Has anyone tried testing the injectors while they are pulled out of the head, but still on the machine? at 260$ a piece i don't want to order any if i don't have to. Previously i pulled all the fuel lines, and filters out and soaked them as well as blew compressed air through everything to try to clean it. I also put a straight edge on the block and head and it appears to be nice and flat.

5030 · Sep 22, 2019

The skirts are scuffed a bit, nothing major. I have to ask, you said black smoke... Did you check the air filter and tract prior to wtenching the engine?

Tractor Seabee · Sep 23, 2019

Black smoke usually is too much fuel or not enough air for proper atomization. Target those two systems first. If it was crankcase oil passing the ring the oil level in the crankcase wold be dropping.

Ron

TimberHole · Sep 23, 2019

Pistons look pretty good. Have you checked their dimensions? I would make my decision based upon dimension.

Roadworthy · Sep 23, 2019

If you opt to go the injector and pump route you can probably have them rebuilt rather than replacing them. A shop that actually works on diesels can do all three injectors for what you'd expect to pay for one new one.

RickB · Sep 23, 2019

TimberHole said:
Pistons look pretty good. Have you checked their dimensions? I would make my decision based upon dimension.

Exactly. And rings are wear items, so they need to be new. There’s good advise above about the fuel system. Focus on that to cure your symptoms.

blakester · Sep 23, 2019

I did pull the air filter right out, and clean all the ports, as well as tried to run it with no air filter, same issue. i'll hunt around for a small engine disel repair shop. How about bench testing them on my machine. I wouldn't get the drip test but at least i could check visulaly for the spray pattern. Is that really enough of a test if I can do that to be confident in them?

Tomtint · Sep 23, 2019

If it were me and I went through the trouble of pulling pistons.. they would be replaced while I was in there..

PILOON · Sep 23, 2019

Tomtint said:
If it were me and I went through the trouble of pulling pistons.. they would be replaced while I was in there..

Yeah, agree. LOL the labor is already there.

MossRoad · Sep 23, 2019

I kinda agree that if you're already in there that far, with 3000 hours on them, you might as well replace them. About how many hours do you put on it in a year? Just curious.