Kubota MX4800 lost all coolant

[dodge man]

I’d probably pull the head next and have a look. It sure sounds like a rod knock but could be a problem up top.

 

[5030]

late model Kubota's are parent bore, no liners. Good try though. next wild guess?

 

[5030]

I removed the rod caps and all the babbit looked like new. If the babbit looks good do you think it's the main crank bearings?

Could be. I certainly hope you have a Workshop manual and you renewed the rod bolts and didn't reuse the old ones and of course torqued then progressively to spec. Do you really know what it's supposed to look like or is that an educated guess. Could be the mains. You are in so deep now that pulling the main girdle is next on the agenda. Glad it's not me. if it was mine, it would be at the dealer. I just don't do that stuff anymore. besides, I hate laying on my back, looking up. Could be a balancer shaft bearing as well. That hammering in your video is most certainly in the bottom end, not the top and the hammering is steady and unwavering which indicates a main or rod. Bottom line is, something is euchred. You'll find it eventually. if it runs after you find it is another story.

Worst case scenario is it turns into a 15 grand lesson. keep in mind that of you screw it up, you don't have a core to turn in for credit either.

I'll be copying the mail on this one.

 

[hube2]

... Glad it's not me. if it was mine, it would be at the dealer...

When I was younger I would probably rebuild it myself. Now it would be going to the dealer or a mechanic I trust if I thought it was worth the expense or the salvage yard if it wasn't. There is a guy not to far from here that would probably take it off my hands and rebuild it an resell it if he thought he could make some money on the deal. He'd probably give me more than the salvage yard would. I no longer have the tools, the workspace, or the desire to do this kind of work.

 

[sd455dan]

I dropped the pan yesterday and the piston rod bearings looked factory new. When I checked the valve clearance to the rocker arm they were all within spec.
If the noise is a tappet, connecting rod, or valve would the gap still be within spec?

I called the Kubota dealer and they said they don't rebuild engines they only replace them. Cost $15k. The tractor was $22k new with $5k loader which means the tractor new was worth $17k new.

I have rebuilt tractor engines before but can't find anything that is damaged.

I would dig deeper from what you posted above.

So you unbolted the rod caps individually and inspected the inserts and they were not damaged?
If plastigage shows normal bearing clearance and crank rod journals are undamaged, i have to wonder if something is amiss with the head.

Loss of coolant is not loss of oil pressure.

If it were mine, the head would be coming off next- to make sure a valve isn't sticking and being tapped by the piston or maybe an exhaust valve seat "moved" when the head overheated with no coolant.
If nothing else the#3 piston crown may reveal if it has been contacting something it shouldn't and confirming others thoughts.

With the prices for a new engine you quoted -not much to lose by digging deeper.