Poor cab heat

dwmaster · Nov 2, 2006

Ya it comes out of the top of the water pump up the left post down the right post then back to an inlet on the side of the water pump. Tried to post a picture but I looks like i need help with that.

dwmaster · Nov 2, 2006

I guess i do know how!!

minimax · Nov 2, 2006

Radmam1, My 3720 looks to be the same as your,out of the water pump and up the left post and down the right post to a "t" and into the bottom of the radiator.There is only one hose with a blue strip on it at the water pump on mine.If you look on JD parts at the water pump there are 2 plugs on the breakdown and they are #24 I think the plug comes out to put the fitting in for the heater feed hose could the fitting been put in the wrong plug hole, so the heater hose supply be on the return side on of the pump so the only water makeing it to the heater core is cold water??????

minimax

radman1 · Nov 2, 2006

minimax said:
Radmam1, My 3720 looks to be the same as your,out of the water pump and up the left post and down the right post to a "t" and into the bottom of the radiator.There is only one hose with a blue strip on it at the water pump on mine.If you look on JD parts at the water pump there are 2 plugs on the breakdown and they are #24 I think the plug comes out to put the fitting in for the heater feed hose could the fitting been put in the wrong plug hole, so the heater hose supply be on the return side on of the pump so the only water makeing it to the heater core is cold water??????

minimax

I don't think that is the case. We measured the return hose temp and it was cooler than the feed hose which comes off the top of the water pump. The feed hose temp was also near that of the engine temp. The flow seems to be in the proper direction.
If there is another port in the water pump as you suggest, then maybe that is the port for the return hose. Then it would be like the picture posted by dwmaster - outflow and inflow ports are at the water pump. This may cure the problem.

radman1 · Nov 2, 2006

joe_ferrari said:
I would say you have more than a poor cab heat problem, your engine is not getting up to working temperature. That is very bad for a diesel. They are designed to run with a load at operating temperature. Not having enough heat in the engine leads to nasty deposits and shortens engine life.

Joe

I'm with you. Engines aren't designed to run that cool. I also notice the exhaust fumes are quite irritating to breath and bother my eyes when when it is running cold. This is more than just normal diesel fumes which don't normally bother me. I think the combustion is suboptimal. This seems to go away a higher operating temps.

CATMAN · Nov 2, 2006

dwmaster's water pump photos don't like like the JD parts to me. His bottom radiator hose at the water pump is on the left side of the tractor(If I am viewing it correctly), but JD Parts shows your water pump bottom hose inlet on the right side of the tractor. If correct, then a design change has been made by John Deere and might explain different results in heater performance between customers/owners of the same model.

dwmaster · Nov 2, 2006

outlets are on the left side. Their is a plastic tee with a cap on it just below the right side of the cab on the return line which must be for bleeding the line.

CATMAN · Nov 2, 2006

Thanks dwmaster for the expanded photo. I see your oil filter is on the left side also. JD Parts shows the oil filter on the right side in their graphics for a 3720 compact utility tractor model. Something it definitely different, if I can trust their graphics.

dwmaster · Nov 2, 2006

Mine is a 4320 if that should matter.

patrick_g · Nov 2, 2006

Check to make sure the control actually opens the valve all the way.

I too have a heater problem with my Kubota. You have to be careful to only just barely move the heat control off of the coldest setting or it will drive you out of the cab. They must have designed the thing for arctic use.

Pat