B7100HST cooling question

EddyG · May 2, 2012

I am new here, and have tried to research this in the search feature but haven't found an answer to my question.

I am a mechanic but not on Kubotas.

My tractor is overheating. Blowing steam from the overflow. I figured the thermostate was not opening.

Does this model have a thermostate? waterpump? I have read that some do not.

In order for me to fix this I am trying to understand the system. where I think the thermostate is may not be. and before I tear into this I am hopeing on some education from here.

Thanks.

steve · May 2, 2012

Eddy
There is no thermostat or water pump. The systen is a thermo-siphon where the hot water from the block rises into the radiator and is cooled. The heavier cool water sinks to the bottom of the radiator and back into the lower side of the block. Flush your system out and replace the anti-freeze. Make sure the upper hose into the radiator is full with A/F or the siphon won't work. Check that the grill and front of the rad are clean. Should work like a charm. No moving parts!

Steve

EddyG · May 2, 2012

Thanks Steve.

I will search on flushing the system and making sure the coolant is totally full. And try that.

I'll be back with more questions if I can't get it working...

kubotasam · May 2, 2012

I agree 100%. When my B7100 starts running hot I need to blow out the radiator with compressed air.

hodge · May 2, 2012

kubotasam said:
I agree 100%. When my B7100 starts running hot I need to blow out the radiator with compressed air.

Yep. You've gotta keep that radiator clean.

Rob · May 2, 2012

hi guys, i do have a query on this guys.
I have a mid production run B7100d and a late run B7100hst-d and both have water pumps.
They both have the side mounted dynamo's unlike you guys that have the top mounted dynamo with the fan on it, whereas mine has the fan on the waterpump.
I have been looking at the kubota workshop manual for the 70mm series engines which does tally up with mine.
By anychance is the D-750A engine fitted to yours only a US version , mine over here it appears to be the D-750B unit as per workshop manual. If so, it may account for why i was having issues with hose diameters between radiators, the larger hoses on the non-pumped engines and smaller ones on the pumped units.
both my 7100's use the smaller dia hoses and both sets of hoses are indentical eventhough there is about a 6 year gap between them.
whereas the rad i got from a late B6100 uses the larger hoses, but it also has the dynamo fitted to the top water outlet on the head and not the side fitted dynamo as on the 7100's.
attached pics of the D750B setup, same as my mine, last pic is also b7100, but same as the late B6100 i took the radiator from with the larger hoses etc.
I reckon its a D750A and a D650A

can anyone clarify things,or am i just going on about a load of rubbish.......
rob

Rob · May 3, 2012

just been out in the workshop and had a look at the 2 B7100's , they both have water pumps and thermostats.

you guys must have way different versions over there.....

Lil Foot · May 3, 2012

you guys must have way different versions over there.....

I was just thinking the same thing..... I've never seen one with a water pump or a thermostat.

Rob · May 3, 2012

It certainly makes you think, i fully understand that you get slight variations in model spec from country to country etc, but there is a major engine variaition going on here.
Its cant be a case of egines being changed through their production life because mine are a late 70 and mid eighties and both have the same design engine, the D750-B.

maybe service dept vic can enlighten us.....

rob

Stumpy · May 3, 2012

I can't remember who but someone with an L175 noted they have a water pump while I do not. The pump isn't listed in the parts books either. I really cannot fathom why they never changed the parts books. I went and looked at all three parts books on kubotabooks.com for the b7100 and none of them show a water pump either. They do show a funky looking alternator behind the fan though.

Rob · May 3, 2012

yep, i can recall seeing similar also.
I seem to have aquired lots of B6000/b6100/7100 etc manuals and workshop manuals over a short period, probably too much to be honest.
In all of the B7100 paperwork , none show the waterpump and thermostat, they dont list the engine version as the D750-b either.
The only manual that actually shows the correct engine and electrics spec as far as my model is concerned is the Kubota wsm.
page attached.

Rob · May 4, 2012

well i appear to have resolved the issue of water pump or no pump,
Its a Uk thing.
I spoke with Kubota UK today and they explained the possible confusion etc, they confirmed that the uk spec 7100's were suppied directly with the 750-b unit which has the water pump.thermostat and side mounted Alternator (not dynamo).
something to do with needing more power hence the fitting of an alternator over the normal dynamo.
This also clears up the issue with wiring diagrams also, the 7100 in the uk have the revised wiring loom which does not appear in the normal 6100/7100 owners/users manuals etc, but is in the kubota 70 series engines workshop manual.

You see, there are a few benafits of living on this little island, not many, but a few.

rob

debilbao · Oct 5, 2013

Hi

I'm interested on add a water pump to my b7001.
I'm not sure if possible, and looking pictures i think there is needed something between pump and piece numbered 1.

Could anyone post part list with kubota references to get more info?

Pictures from a d750 with pump on it, would help to.

Thanks in advance.

hampshireborn · Oct 5, 2013

Hi all
I agree with rob i to have a B7100 HST and that has a water pump and thermostat.

dotty · Dec 6, 2015

steve said:
Eddy
There is no thermostat or water pump. The systen is a thermo-siphon where the hot water from the block rises into the radiator and is cooled. The heavier cool water sinks to the bottom of the radiator and back into the lower side of the block. Flush your system out and replace the anti-freeze. Make sure the upper hose into the radiator is full with A/F or the siphon won't work. Check that the grill and front of the rad are clean. Should work like a charm. No moving parts!

Steve

I just installed a Davies, Craig electric water pump with controller on my B7100HST. It took a couple of afternoons and several trips to Autozone for hose, etc. So far it works well, no overheating even after lugging engine with box grader. $400 online from Pegasus Auto Racing Supplies. Well thought out kit.

kubotasam · Dec 7, 2015

Sure would like to see some pictures and if you could, post the part number of the water pump and controller.

Thanks-- sounds like a great mod.

dotty · Dec 8, 2015

Remote water pump info

kubotasam · Dec 8, 2015

Interesting set up. I never thought of putting one in the lower radiator hose.
Thanks for posting the pictures.

85Hokie · Dec 8, 2015

dotty said:
Remote water pump info

SO is that a variable speed pump?

Reason I ask - looking at all those wires I bet it senses heat and when to cut the pump on?

otherwise a typical pump would circulate water all the time - and the engine would take a good while to get to operating temperature!

Looks like a nice setup - other than the cost!

dotty · Dec 9, 2015

Yes, it is variable speed. When engine is cold the pumps runs for 10 seconds off 30 seconds at 6 volts. At 36 F below setpoint pump runs 10 seconds off 10 seconds at 6 volts. At 9 F below setpoint pump runs continuously at varying speeds to control temperature to setpoint.

The magic of microprocessors. I bought the EWP80, the photo in the post is the EWP115.

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