Poor cab heat

[radman1]

Not yet, I sent the dealer the link to this thread hoping I didn't have to go through all the same worthless efforts you have endured but he came back with the same suggestions about the air conditioner switch on, air in the lines, blah,blah,blah, so apparently JD still doesn't have a grasp of the problem. I'm not very happy with JD right now.

Yea, JD corp doesn't have a handle on this problem. It seems like they are waiting for a field guy to come up with a fix. Service manager is coming out to my house on monday (2 days) to try other solutions. We are going to try rerouting the return line to the left side of the water pump. There is a plug there. (#25 on JD part list) Remove that plug and add a threaded insert with attachment for return hose.
There is also another plug near the suction side of the water pump (#24 on part list) which has an oil cooling water line going into it. May also try putting a "T" threaded fitting in that port - one for the existing oil cooling line and the other for the heater return hose.
Another thought would be plumbing the return hose into the plug on the left side of the block where the engine block heater goes.
We also are considering putting a restrictor in the return hose line to slow down the flow.
We are also going to install a new thermostat and make sure all the gaskets are in place around the thermostat as suggested by catman. The thermostat had been previously checked in hot water and seemed OK.

I did clamp my heater return hose yesterday with a vise grip and then started the tractor cold at 29F and windy. At fast idle the temp gauge was 1/2 way over (in the green range) in 11 minutes. Removed the clamp and temp began falling a 1-2 minutes to 1/4 way over. Took tractor out and did hard blading work for 10 minutes and heat went back up to 1/2 way and heat in the cab. Worked tractor for 10-15 more minutes then let it idle. It took about 15 minutes to eventually cool the engine/water back down and blow cool air again in cab.
My dealer just got in a new 3520 cab and checked it for heating this am at <30 outside temp and it performed normally. Heated up to the 1/2 way point in 10-15 minutes and 98F at the vents in the cab at no load. This tractor is plumbed exactly like the 3720 and had an engine block heater installed just like mine. The 3720 has an intercooler but this is in no way connected to the water cooling system.
I'm also considering putting some foam insulation wrap around the feed and return hoses to keep the heat in.

 

[CATMAN]

radman1, While the JD service dept. have the thermostat out; have them look inside its bore and see if there might be a casting flaw/crack in that area. If you will notice how close #24 upper plug(current heater supply connection) is to that bore of the thermostat, then it is worth a good look anyways. You might mention to them about testing the intake air heater and make sure it is working properly. (Engine needs to be cold to test properly). The idea of an intake air heater on a diesel engine is to warm the incoming combustion air during cold start up to help eliminate white smoke complaints and improve combustion heat inside the cylinders until coolant temperatures increase to a programmed/preset level. Although, this wouldn't explain your cooldown after you worked your tractor hard and had it up to operating temp. Your service manager brings up about the air conditioner system being on; What if the A/C controls aren't working properly and the A/C is constantly ON? Is there an easy way to remove the A/C compressor(pump) v-belt and this would isolate that system from possibly removing any heat from the cab heater under the roof. I won't instantly jump on rerouting heater hoses as a first step, because other 3720 are operating properly with that same circuit of coolant flow. The A/C problem does make a lot of sense, because it removes heat from the cooling system circuit and the engine can't generate enough heat to compensate for that loss at light loads. Good luck on Monday and keep us informed. PS. This would also explain way you can clamp that heater hose circuit and the engine temp rises(this also isolated the A/C and cab heater area from any coolant flow and an improperly working A/C system couldn't effect the entire cooling system in a negative way)

 

[radman1]

radman1, While the JD service dept. have the thermostat out; have them look inside its bore and see if there might be a casting flaw/crack in that area. If you will notice how close #24 upper plug(current heater supply connection) is to that bore of the thermostat, then it is worth a good look anyways. You might mention to them about testing the intake air heater and make sure it is working properly. (Engine needs to be cold to test properly). The idea of an intake air heater on a diesel engine is to warm the incoming combustion air during cold start up to help eliminate white smoke complaints and improve combustion heat inside the cylinders until coolant temperatures increase to a programmed/preset level. Although, this wouldn't explain your cooldown after you worked your tractor hard and had it up to operating temp. Your service manager brings up about the air conditioner system being on; What if the A/C controls aren't working properly and the A/C is constantly ON? Is there an easy way to remove the A/C compressor(pump) v-belt and this would isolate that system from possibly removing any heat from the cab heater under the roof. I won't instantly jump on rerouting heater hoses as a first step, because other 3720 are operating properly with that same circuit of coolant flow. The A/C problem does make a lot of sense, because it removes heat from the cooling system circuit and the engine can't generate enough heat to compensate for that loss at light loads. Good luck on Monday and keep us informed. PS. This would also explain way you can clamp that heater hose circuit and the engine temp rises(this also isolated the A/C and cab heater area from any coolant flow and an improperly working A/C system couldn't effect the entire cooling system in a negative way)

We have watched the a/c compressor and it is not engaged/running during our tests. That was one of the early considerations.
We will check out your other suggestions as well. Thanks for the help.

 

[CATMAN]

Radman1, Did JD come out and try anything worth sharing with us on Monday?

 

[radman1]

Radman1, Did JD come out and try anything worth sharing with us on Monday?

Update. Service mangager has decided to wait at this time before trying any modifications. JD corp recommended he not try anything at this time and let them figure out a solution. My dealer tried to order a new 3720 cab from JD corp and they are putting tractors on hold for no sales til Jan. I don't know if this is just for that model with cab or if other tractors are involved. Dealer thinks it is due to the cab heating problem but JD corp won't say.

 

[CATMAN]

Radman: your idea for insulating your heater hoses is just what semi-truck manufacturers do when they install their "Arctic " package for cold weather applications. They wrap heater hoses and fuel lines. I don't know how much you will gain, but it should be pretty cheap and simple, so I would go for it. I do have a question for you: Are you able to leave the cardboard in front of the radiator(JD installed) when you worked your tractor the other day or did you remove it? Just curious. I assume you left it in.

 

[radman1]

Radman: your idea for insulating your heater hoses is just what semi-truck manufacturers do when they install their "Arctic " package for cold weather applications. They wrap heater hoses and fuel lines. I don't know how much you will gain, but it should be pretty cheap and simple, so I would go for it. I do have a question for you: Are you able to leave the cardboard in front of the radiator(JD installed) when you worked your tractor the other day or did you remove it? Just curious. I assume you left it in.

The cardboard has been removed from tractor past 2 weeks. All the recent posts, temp reading and when working the tractor have been without the cardboard in place. Engine will heat up to operating temp in 10-11 minutes if I clamp the heater return hose.

 

[turbo36]

Update: My dealer is going to change from the 160 degree thermostat that comes with the tractor to a 180 degree used in other JD equipment, Also, they said something about checking the mechanical cable that goes to the heater control.

 

[CATMAN]

turbo36; Did your dealer say if this was their idea for these changes OR did that info come from the factory engineering group? Just curious if you happen to know?

 

[turbo36]

This is a dealer idea. I sent my dealer the link to this thread but they pretty much blew it off so I will let them try what they want while I contact Deere directly to see if I can get a response.