Kubota B7500 overheating

Sacwarrior · Jun 27, 2012

I have a Kubota B7500 with bucket and RCK 60 24B mowing deck with around 660 hours. I lubricate the deck every other time I mow. In the past on really hot days while mowing my 4.5acres of grass it might overheat. When it did, i would stop, clean the filter and grille and the temperature gauge would drop quickly. Today it went over the red line but there was little grass blocking the air flow. I went back to the barn and blew off the grille and filter as well as the radiator. The fan belt seems to be fine, no noise coming from the water pump housing. I flushed the radiator until clear and the temperature gauge stays above the red with the PTO off. The service department where I bought it suggested I take the radiator out and take it to a radiator shop. Any other thoughts before I try to do that?

bigdeano · Jun 27, 2012

I presume it has a thermostat like most water cooled engines.I would take it out and check it in a pan of water on the stove to make sure it's opening far enough and at the right temperature.

rswyan · Jun 27, 2012

Sacwarrior said:
The service department where I bought it suggested I take the radiator out and take it to a radiator shop. Any other thoughts before I try to do that?

Yeah - take off the radiator cap when cold and then fire it up and let it warm up.

Observe the temp gauge and if it goes up towards the red stick an actual thermometer into the coolant and take a reading.

All that may be bad is the sending unit for the gauge ....

petegoud · Jun 28, 2012

Have you checked that the radiator isn't plugged with dirt and grass impeding the flow of air through it thus preventing it to cool? That was the problem with mine when I first bought it, and it had been serviced by a Kubota dealer several times for overheating.

Sacwarrior · Jun 28, 2012

bigdeano said:
I presume it has a thermostat like most water cooled engines.I would take it out and check it in a pan of water on the stove to make sure it's opening far enough and at the right temperature.

I flushed the radiator and let it stand overnight. In the morning when I turned the ignition on the needle went back to the red line. I should have figured then that it was probably the sending unit or a connection, but I took out the thermostat and found it was stuck OPEN. Not a problem now, but a different issue next winter. I found the sending unit on the right side of the engine near the firewall and wiggled the wire coming out of it and the needle went to dead zero. I'll probably have to replace that and the thermostat at some point. Meanwhile I was able to mow for about an hour and a half today with no evidence of overheating. The gauge did flicker on some bumpy hills, so I think the connection is bad there.
Thanks to everyone who offered suggestions.

aczlan · Jun 28, 2012

Sacwarrior said:
I flushed the radiator and let it stand overnight. In the morning when I turned the ignition on the needle went back to the red line. I should have figured then that it was probably the sending unit or a connection, but I took out the thermostat and found it was stuck OPEN. Not a problem now, but a different issue next winter. I found the sending unit on the right side of the engine near the firewall and wiggled the wire coming out of it and the needle went to dead zero. I'll probably have to replace that and the thermostat at some point. Meanwhile I was able to mow for about an hour and a half today with no evidence of overheating. The gauge did flicker on some bumpy hills, so I think the connection is bad there.
Thanks to everyone who offered suggestions.

I would use some pliers to squish the plug onto the sender a little so that it has a better connection.

Aaron Z