D4 5T problem !

My bet.........Piston came apart. CAT had lots of designs over the years and one was a 2 piece where the top actually screwed onto the base and had a pin to lock it. Folks usually report they got showered by small bits of hot aluminum.

Finally I have had the time and weather to have a look at the engine.
On taking the head off I noticed a little hole in the rear piston so went onto take the piston out.

Here are some pictures of the piston.
I just wonder if anyone knows why it happened, what the probably cause was, as I am thinking that all of them may go the same way soon.
I am on a real tight budget with it, so very reluctant to replace all the pistons even if I could find some, but would hate myself to put it back together and the others fail in the near future.

Also the valves on the same piston appear to protrude a little, which I have never seen in my limited experience, I have to get a valve tool before I can get them out to have a good look.

The bearings look a little pitted, is this acceptable? I will only be using the dozer for around 100 hrs a year and hopefully for many years to come, winching out logs in the winter from the bush. So if I need to replace them to keep it going I will but obviously will have to rob a bank first 😆

That small amount of pitting won't hurt anything. But do check the clearances and what is the condition of the journals? That pitting is most likely caused by acid etching, combination of water in the oil and infrequent oil changes.

The element of time and a poor design is probably what got to your piston/s, not much you could do about it. May be able to find some good used one piece pistons, nothing wrong with that if the ring land clearances make spec.

On the valve protrusion, you need to check seating, possible some of the piston material got trapped in there.

Hi Team,
broken piston rings usually produce the piston ring land erosion failure pictured. Spec = 0.010" max. side clearance between ring and groove.
The valve heads on later D4400/4600 engines can protrude up to 3/32" for exhaust, and 1/8" for inlet. Early D4400/4600 engines had pocketed valves--as you recall.

Maybe swap the big-end bearing shells from upper to lower etc. if the clearance is in new spec. = 0.0055"-0.008"
Max. is given at 0.013" for aluminium bearings.
Hope this helps.
Cheers,
Eddie B.

I agree that at 100 hours a year, I would try to replace only one piston.

Thank you so much for the replies.

I will try and find a piston for it and check the clearances on the others.

Does anyone know where the best place to find one or person to speak with in the Ottawa area?

Thanks again for the help and advice.
Yogi

I check tomorrow if am still have some piston and located near MONTREAL

Fantastic, Thank you

Yogi