Kubota D1402 rebuilt with low compression

[cyberflyrg]

I bought a Kubota that has the D1402 engine. At the time I bought it, it did run barely, very little power, very hard to start even with starting fluid(I know, ugh). I bought it cheap, so I can invest some in fixing it. The guy I bought it from installed 3 new pistons and the bearings, new head gasket,etc. The engine has a lot of blow-by coming up through the lifters and pushrods. The guy did a poor job of rebuilding and was a real amateur. My guess is that he never did hone the cylinders because when I took the head off, they were slick and shiny. Good news was there was no ridge at all in the cylinders, engine has 1200 hours on it. Im not sure why they tried to rebuild it, but they hacked it up for sure. I have the head off now and will pull the bottom end (pan) off tomorrow. Im hoping the crank and journals are still good, but who knows what I will find. Engine had about 150PSI of compression on two cylinders and 110 on #3cyl, which is pretty low for a diesel. He told me there was about 10 hours on the rebuild when he sold it to me and I have put about 1.5hours on it.
Im assuming that if I remove the pistons, I can hone/break the glaze on each one and put it back together, if crank and bearings are ok. So some questions for the experts:
1) Can I hone the cylinders with the crank in place if I protect it from the grit???
2) Should I put new rings on the new pistons or can I save the current rings since they only have about 12 hours on them?
3) My hone is the ball type hone with 240 grit balls, is this ok for this job?
4) Anything else I should do while I have it down for repairs??


Thanks for any help you guys can give.

Ron:cool2:

 

[SimS]

Ron;
The D1402 should be a sleeved engine. Does it look like the PO actually did a rebuild? You know like new gaskets, excess RTV sealer, etc.. You might want to bite the bullet and throw a complete kit at it and be done with it. OTOH mike out the pistons and sleeves and see if they are within specs after you hone. See if the current rings are shiny like the bores. If they are there is probably more than 12 hours on the rebuild.

SimS

 

[art]

You might have some misfit parts or poor installs such as ring end gap. So if he didn't hone and the sleeves are glossy Then you should hone and check his rings! Do make sure the thermostat is good as well. Glazed cylinders are a sign of running cold not really getting the engine warmed up properly.

 

[cyberflyrg]

Yes, the PO did try to rebuild it, he gave me the left over parts, I have the rebuild kit receipt and left-over gaskets and boxes (pistons, rings and bearings). And the pistons look new, so Im going to pull them out tomorrow and see what I have. Ill know better then what to do next.

 

[The Fred]

Measure the bore before you attempt a fix. If you can't do this find someone who can. The specs should be online somewhere, Google is your friend.

Regards and good luck. Doing it right the "second" time is always fun.

Fred

 

[sd455dan]

I bought a Kubota that has the D1402 engine. Engine had about 150PSI of compression on two cylinders and 110 on #3cyl, which is pretty low for a diesel.

Those compression #s are less than on many gas engines.
Very surprised you were able to start it. i wouldn't be surprised to see a spec of 360 to over 500 psi for a new engine.




He told me there was about 10 hours on the rebuild when he sold it to me and I have put about 1.5hours on it.
Im assuming that if I remove the pistons, I can hone/break the glaze on each one and put it back together, if crank and bearings are ok. So some questions for the experts:
1) Can I hone the cylinders with the crank in place if I protect it from the grit???


I have done this a few times and you must be Very careful to keep the grit from getting on the crankshaft or inside of the block. Clean rags or paper towels stuffed over the crank in the best position to avoid getting the hone involved with the rags (easier said than done).
Clean the bores really well after honing and wipe the crank throws and journals spic and span clean to.


2) Should I put new rings on the new pistons or can I save the current rings since they only have about 12 hours on them?

Check the ring end gap is within spec. Also most new top compression rings have a coating that helps with startup and seating so if the rings aren't to expensive it might be worth it to just replace them. Check the bores for concentricity and the piston to bore clearance is within spec.

3) My hone is the ball type hone with 240 grit balls, is this ok for this job?

I have the other style but i think that the grit is probably coarse enough and not to fine.

4) Anything else I should do while I have it down for repairs??

I would check the head and block for flatness and machine the head if it is warped.
You can have loss of compression due to valve /seat/ guide problems. (a problem I have had)

It may be a good idea to have the head re-conditioned to.

Replacing the rod bearings if the crank is in good shape can buy you a few extra pounds of oil pressure to.


One other thought you stated the pistons and rings are new ,

in my opinion even with glazed cylinders those compression #s are to low If you are sure the (compression gauge and test were accurate)- I would check the piston bore clearances ( bore concentricity) and ring gap closely, also the head , valve- rocker clearances, and cam- crank timing something seems more amiss than just glazed cylinders.

hope this helps and good luck:thumbsup:

 

[Scott65]

Agreed, have cylinders and pistons mic'd. If it's all still standard sizes and you can see any cross hatch, it hasn't lost too much meat but check for out of round. Particularly the cylinder right where the water comes in.

I recently rebuilt a Kubota but i don't remember the specs. That definitely seems low. Either way, if you have blow-by, your losing compression. It has to be ring, piston, or cylinder related. That's how it gets into the crankcase. The hone you have will work, and would even be my preference. Especially if the crank is still in. A stone type, your nearly guaranteed to hit the crank and break the stones.

As others said, have the head checked and surfaced. It is important to know if the previous rebuild included a resurface. The pistons come above the deck of the block. If you remove too much from the head, the valves and pistons collide, injector tips, etc. They make shim gaskets for this, so you have to know how much material is removed. If you found one of these shims under the head, but the guy didn't resurface the head, this is part of your compression loss as well.

 

[Joisey]

I understand that this thread is over a month old, but I have a thought on your blow by trouble. The piston rings may be put on the piston incorrectly. Most times there is a top side to the rings and a taper on the inside edge of the ring which uses compression pressure to help seal the ring to the cylinder wall. Other than what has been mentioned, you may want to check the ring end gap. The rule of thumb is .004 of end gap for each inch of cylinder bore. So a 3.5 inch diameter cylinder would have a ring end gap of .014 As always, it is best to go with the engine or ring manufacturers recommendation for end gap installation on the piston. I hope you find the trouble.

Some people either don't check the end gap, or go crazy with a file and create too much of an end gap.

 

[Raw Dodge]

Irregardless of whether or not there's a ridge onThe cylinders,they need to be checked with an inside micrometer for out of round and taper. one of the posters said it was a sleeved engine,if that's the case and you are into it cheap,I'd do a full kit new sleeves and the works,call it done no honing no worries about it sealing after..