No heat in cab

BillinAZ

Member
This seemed like the best page to pick some brains for help. I have a 2005 Kubota M8200 w/Ultracab. In prepping for cold weather I can't get any warm air blowing in the cab. Temps outside in the 40-50s. Was no warm feel to the bottom radiator hose or heater hoses. Installed a new thermostat (didn't "appear" to be any problem with the old one), still no heat in cab. Temp guage comes up on dash, but maybe not as far as what I remember. This is after engine has run for 20-30 minutes, no load on it. What am I missing? Winter is coming here in NE Missouri. Thanks
 

Assuming the heater used to work?
The heater core supply should be tapped from just below the stat. The heater core coolant should return to the suction side of the water pump.
Odds are the heater core and/hoses are "vapour locked" with air.
Is the heater core coolant control valve actually open?
 
Hoses do tap off right below thermostat. The temp control in the cab is just a rheostat type knob and the hoses rise up thru one of the cab frames which you could always feel was warm to the touch, but not lately. Air lock sure makes sense. How would I get it 'primed' or check to see if there is fluid in that hose. There are no visible connections, and where the hoses come out looks tough to get to. Thanks.
 
I had a suspicion that there might be a valve in the line, I just looked up on Kubota's parts sight and is shows a valve in the line on tractors below serial number 11018. Not sure if it a mechanical valve or electric.
 

Both the Ford I have now and the Case that I used to have, have a valve in the line next to the motor that you open in fall and close in spring to keep heat away from the cab when you don't want it. Don't expect it to give off much heat if the gauge is still low, and don't expect the gauge to come up much until you start to work it.
 
Get the engine up to temperature, set the throttle high, heater blower on.

Feel the heater hoses near the heater core.

Neither hose is hot: No flow, coolant level low, there is a controll valve that is closed or malfunctioning, heater core is clogged internally, kinked or internally collapsed hose.

One hose hot, one cool: Restricted flow, same as above but flow is insufficent to transfer enough heat.

Both hoses hot: Air flow through heater core is blocked.

If you determine there is lack of coolant flow, shut off engine, relieve presssure on system, be sure system is full of coolant.

Note the flow of the coolant, the hose connected near the thermostat housing will be the "out from engine" connection. The hose connecting near the water pump or to the radiator will be the "return from heater" connection.

Remove the "return from heater" hose, block the hose barb, hold the hose over a clean container, have an assistant momentarily start the engine. Coolant should full flow/gush from the hose.

If restricted flow is found, reconnect the line, remove the "out from engine" hose from the heater core, place it on the container, start the engine. It should gush. If it does, the heater core is clogged. If not, the restriction is in the hose from the engine, the fitting, valve, etc.

Remember to return the discharged antifreeze betwene each test, you only have a couple seconds of flow before the level drops below the pump impeller.
 
Both hoses at heater core are cold-fact is-no coolant is getting to the core at all. I have checked for blockage,kinks, etc. with light forced air and both sides flow fine all the way down to the pump and outlet at the thermostat. I removed the thermostat(again) to get a peek at the inside of the outlet-no blockage. Radiator is topped off-ran for 15 minutes with cap loose, another 15 minutes with cap on, level did not drop? Radiator felt warm, but not really warm. Radiator hoses-upper warm, lower a little warm, almost like it is just engine warmth spreading to them. Could the water pump totally fail without showing any external evidence and not overheating the engine quickly? Why else, if no blockage would no fluid be getting to the heater core? Thanks guys.
 
Did the heater ever work? If not possibly both hoses are connected to the "out" ports. One needs to connect near the thermostat housing, the other must be on the suction side of the water pump, near where the lower hose connects to the pump. Look for an unused plug or capped off hose barb. Move one heater hose there.
 
I bought the tractor new and have never had a problem with the heater before. Even with supply hose disconnected at heater core and engine running no fluid makes it up to there.
 
Just a thought and I am no kubota expert by any means. I remember a john deere 4040 that had a 6059 replacement engine in it, well at some point it needed an overhaul and the engine always ran on the hot side, upon teardown of the water pump it was discovered that the impeller was plastic and it wasn't driving.

Not sure if that is possible on the kubota or not.
 
Dad had a Rambler 6 that the impeller broke off too. Just all of a sudden the temp was higher than normal, acted like the thermosiphon systems. With the radiator cap off while hot there was hardly any coolant moving. Removed the water pump, impeller was laying in the block.
 
I found a broken plastic impeller in I think it was Mazda motor a few years ago.
 
It is sounding like a lack of circulation. I have seen pump impellers break, but always caused overheating. I guess it's possible the coolant could circulate just enough through convection to still cool the engine...

My next move would be to pull the water pump and see what's in there. Possibly there is something sucked into the impeller, impeller loose, broken...?
 
Some manufacturers use a valve to cut off hot coolant flow to the heater heat exchanger during summer operation. For winter operation you have to open that valve to get hot coolant to circulate through the heater core.

Some times if you drain the coolant you have to run the engine with the heater temp control wide open and the engine at high rpm to "refill" the heater core on the tractor roof.
Your operator"s manual should describe both of these issues.
 
Are you using the tractor, or just idling?? My White will not put out heat unless it is wound up. Not sure on your Kubota, but on my tractor, the water pump has to push the coolant, about 15'...uphill.....unless rpm's are up...it won't do it.
 
The place i worked use to sell case tractors in the 50s 60s and 70s. The cab tractors had a bad habit of air locking in the cab heater core. We would turn the heat to the hotest setting and take both of the cab hoses off and force water through them with a garden hose and once the hoses were full we would clamp them with needle nose vice grips . then we would hook them up and warm up the engine when it got to operating temp. we would take the vice grips off . this usually worked but some times we had to do it twice.
 
All is well, thanks so much you guys. I finally went full throttle in road gear, heat came out after about 30 seconds. ?Guess the pump just really needed to wind up to get it up to the cab.
 

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