Little knowledge from b7100 mechanics

[tlefire]

New model hst....
Cutting grass and busted a lower radiator hose. Parked it, drained radiator (about 3/4 gal left), ordered a new radiator hose. Had a small leak on the pipes from the fuel pump, ordered the o rings and washers for that. Replaced those and the radiator hose, bleed the system, and new 70/30 radiator fluid. Started tractor and had no leaks. Cut about 2 acres and noticed tractor bogging down on higher grass with a little black smoke, but not bad. Figured I didn't get the fuel system bleed very good, so had wife crank while I bleed fuel pump about 15 seconds. Cranked tractor to test and after 1 minute noticed water from the radiator leaking again. Shut the motor down and while looking for the leak found that it was coming from behind the dynamo. Would only leak when motor was almost wide open. At idle, no leaks.

Head gasket, cracked block, or ?

Tractor has 850 hours. I do have a service manual.

Thanks for any help.

 

[Russell King]

Why did the radiator hose bust? Did you run it hot or does the temperature gauge work?

No help on the leak but please clarify that you have the dynamo behind the fan or is it mounted to the side like an alternator on a car?

Do you have a water pump or is it a thermosyphon system?
What you describe sounds like a leaking water pump to me but I have no idea if that tractor has a water pump.

 

[tlefire]

Hose was a braided type hose put on buy the previous owner. I've had the tractor 8 years. That hose was not a formed hose and split where it bent going into the motor. Did not run hot.

The dynamo is behind the fan.

No water pump.

 

[Russell King]

If it didn’t overheat I would not be suspicious of the head warping.

Is it leaking near where you were doing any of the work? There may be a loose plug back there. You can look at Kubota USA illustrated parts list and see what could be leaking.

Since there is no water pump the water may not get to the leak until the heat gets the water moving a lot.

There are several people that should be able to help much more than I can.

 

[ken erickson]

There is a gasket on the back side of the casting for the dynamo stator. As I am sure your aware that casting also serves the upper radiator hose. Perhaps loose bolts or a bad gasket. If you do end up removing to service the gasket it might be a great time to inspect and replace the dynamo bearings.

 

[tlefire]

Thanks Ken. I knew that casting was part of the system. I wondered about that gasket or a pinhole in the casting. From your picture it looks like the water is coming somewhere around that bottom middle hole just to the left of the radiator hose. I will probably remove the dynamo and replace that gasket and bearings, put it back together and see what happens. One thing I failed to mention was there is no water in the oil or oil in the radiator fluid.

Thanks for your help.

 

[ken erickson]

The nut and stud you mentioned , and the one I pointed to in yellow, is the one that is notoriously difficult to access and get a wrench on. Some great posts here on OTT detailing how to make the job easier.

i think it bodes well you have not overheated the engine and that there is no mixing of oil and coolant .

Good luck on your repair!