Kubota B7001D engine repair

[gazza]

Hi guys, as per my previous email I just bought this Kubota with a dead engine, here are the details.
It was sitting for quite a while and leaked oil when trying to start, was recently turned over and it looks like it is hydraulically locked up.

It was listed a having a "Oil leak" (no visible oil leaks so I assume its from the dipstick tube)
Engine has plenty of thick black oil, about 4lt drained out.
No water in top of radiator, no water in the sump apart from a few drops of bright green coolant which may have happened during the transport home. I would guess that the water level in the radiator was about level with the top of the block.
Engine does move (as in not seized) when gently turning the engine by hand you can hear water being pumped out the exhaust.

So assuming it has either a blown gasket/cracked head or cracked block I started to carefully dismantle it.
First thing I came across is the exhaust has water in all three ports and the manifold. It looks like one cylinder has filled with water with the exhaust valve open and this has allowed the water to flow through the manifold into the the other exhaust ports up to the same level. I would guess at cyl number three as having the leak as this one seems to have the most water discoloration.

I will remove the cyl head tomorrow to see the damage, anything else I need to look out for??

cheers
Gazza

 

[bruceatlam]

Rain water??

 

[gazza]

Rain water??

Actually I did think of rain water initially but it has a horizontal muffler and exhaust pipe. It is possible that the previous owner gave it a wash with a blast up the exhaust pipe. I did notice that overall the tractor has no mud/dirt and no oil leaks so I am guessing it got a high pressure wash at some stage.

cheers
Gazza

 

[maximus]

Hi Gazza,

Guess you won't know until that cylinder head is off. What are the frost pockets like? Has it been kept in a really cold climate?

Keep us informed - looks like you've got a great project there.

Chris

 

[B7100]

I would perform more diagnostic tests before removing the head in case its hard to see where the water is coming from and how much.
You already have the exhaust manifold removed,I would take out the injectors,drain the water from rad and blow or suck any from the cylinders.
Refill the rad and turn over to see which cyls have water in them.You can also pressurise the cooling system through the rad filler.
All this may seem a bit fussy but once the head is off and if the head gasket looks ok it can be difficult to see what else might be cracked.
dave

 

[gazza]

I would perform more diagnostic tests before removing the head in case its hard to see where the water is coming from and how much.
You already have the exhaust manifold removed,I would take out the injectors,drain the water from rad and blow or suck any from the cylinders.
Refill the rad and turn over to see which cyls have water in them.You can also pressurise the cooling system through the rad filler.
All this may seem a bit fussy but once the head is off and if the head gasket looks ok it can be difficult to see what else might be cracked.
dave

Hi Dave, I can see where this type of diagnosis would be a great help to find the cause of the problem. Unfortunately I have already removed the head. I did consider checking a few other things before I removed it but not knowing the manner in which it stopped working I assumed it had a few cylinders full of water and my intentions were to drain this out without turning the engine over and possibly doing more damage to the bore.
Gazza

 

[gazza]

Well after a couple of hours work (just working carefully and slowly so as not to miss anything) the head is off.
First thing I found was a broken head bolt between 1-2 cylinders, both the head of the bolt and washer were sitting on top of the head so no other damage involved from these pieces.
Interesting, all three cylinders were dry apart from a bit of condensation on the top of the piston no 2, yet no 1 and 3 cyl had water stains on the head. Also it looks like the engine was stopped with all 3 pistons at the top of the bore, could no 2 cyl have been filled with water and then pumped into the exhaust port of no 1 and 3 cyl?

The broken stud may be the cause of the problem or could it be the result of something else?
The gasket looks like it has been leaking between1-2 cylinder and there are 2 x 3mm water gallery holes between these, maybe it has only been run for a short time in this condition. Remember there is no water in the oil or oil in the water but the exhaust manifold has been filled with water at some stage. Do these heads crack between the water jacket and the exhaust port?, it could have cracked above cyl no 2 and then the water flowed into no 1 and 3 port.
Even the water stained head could be from water seeping past the closed exhaust valve back into the cyl.

Is there anything else I need to look at before I dismantle and clean the head?

Thanks to all of you who are helping with this diagnosis,
cheers
Gazza

 

[gazza]

Well the bad news is the head is definitely cracked between the valves on no 2 cylinder. This brings me to a couple of options.
Find another head or has anyone had any success in having one of these welded up?
I know there are a lot of similarities between the D750 and the D950 engines, but will the D950 head fit onto the D750 block?

cheers
Gazza

 

[SpudHauler]

If it is cast iron, they are very hard to weld properly.

Not many welders would even consider trying.

Do an internet search for "Kubota engine rebuild" and you should find lots of new or used sources.

 

[peter50]

This method over many years and recommend that you do not assume the trouble is a certain part, as a problem in one area will often show up as a symptom somewhere else. An example is carb malfunctions are often incorrectly assumed to be governor problems.
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