Poor cab heat

[radman1]

OK, today I ran my next official experiment using a HF infrared heat gun. New 180 thermostat installed. Outside temp by heat gun of 39F. All measurements made at fast idle of 1300 rpm. Engine temp measured at top of water pump just behind the thermostat housing. Radiator measured at top on black area. Vent temp measured in cab.

Start at 9:42: heater control valve all the way open and fan on low speed
engine - 39F

10:00
engine - 93
vent - 76

Now close heater control valve and shut off fan

10:11
engine - 134
radiator - 40

Clamp return heater hose, fan and control valve remain off

10:21
engine - 170
radiator - 76

Unclamp hose, turn heater control valve fully open and fan on middle speed

10:26
engine - 134 (temp gauge on tractor dropped very rapidly in 2-3 minutes)
vent - 97
radiator - 89
The engine and vent temps remained stable for an additional 10-15 minutes.

At 10:40 shut off fan and heater control valve,

10:51
engine - 164
radiator - 78

Opened heater control valve and fan on middle speed.

Several minutes later
engine - 134-135
vent - 99
radiator - 78

The new thermostat did not obtain operating engine temp unless the return heater hose was clamped. However, once all fluids and engine warmed up, the cab heat could be maintained with new thermostat which was not possible with the old. I still think the return heater hose being plumbed into the lower radiator hose near the radiator is the problem and mixes with the much cooler radiator water. It looks like it could be plumbed into the radiator hose closer to the water pump by several inches and this may cure the problem.
In our initial tests, the max engine heat with the original cooler thermostat with the heater hose clamped was about 146 (156 thermostat). Now it is 170 with new, 180F thermostat. Previously when the heater hose was unclamped, the max engine heat was 114 with the old thermostat. Now it is 134 with the new thermostat.

 

[CATMAN]

Nice to see that JD made a little progress on your tractor. Was this with their special cardboard in front of the radiator or not? I assume you would like to see more improvement. Your idea about insulation on the heater hoses is still a cheap option. I think it is going to take more investment from JD to be able to get those temps up to operating temperature with engine at no load status. I sometimes wonder if this tractor was first designed without a cab, then due to customer interest/competition a cab design was added. Tractors without cabs have no heater cores that remove heat=no problem. Add cab=removal of heat. I feel engine block insulation, oil pan insulation and electric, temperature controlled fan clutch addition may be necessary. All these are expensive. You may find JD telling customers to warm up tractors for 20-30 minutes, then begin their work and temperature will rise accordingly. I wish some of the other posters in cold climates with 3520/3720 cab tractors would post their ambient air temps and their heater performance now that we are in the month of December. Actually your ambient air temp of 29F isn't really that cold for Nebraska. I'm sure you will see 0F before winter is over and your heater core temps are going to worsen according.

 

[radman1]

Can't let this thread die or let JD off the hook. Dealer will pick up tractor the day after christmas. Service manager, regional rep and JD tech had conference call yesterday. JD tech wants them to adjust the injector timing to see if that will change the heat of the engine for the next trial at trying to fix the cab heat issue. Will keep you posted.

 

[dwmaster]

I was wondering if maybe its running a little rich and thus running cool. If they could lean it out that would warm it up.

 

[turbo36]

Radmad; dwmaster, that is an interesting theory, I put 10 hours on the tractor last weekend building a rock wall and every time I got close to the exhaust my eyes would burn like the tractor was running rich, also when I was done for the night and washing down I noticed a lot of soot on the FEL. Hmmmmm, I thought this was an electronically controlled injection system designed to meet the new EPA requirements?

On a positive note the tractor is so much exceeding my expectations of comfort and performance that I have long forgotten the purchase price.

 

[ACKBill]

I was wondering if maybe its running a little rich and thus running cool. If they could lean it out that would warm it up.

That's a great thought. I'm not sure changing the mixture on a diesel has as dramatic effect as in a gas engine but that's food for thought! Especially if turbo thinks it's running rich...

A bad controller or a defective sensor could easily mess up the mixture in all the cylinders. How about it, anybody out there know enough about tuning diesels to weigh in?

BILL

 

[RFB]

It has always been my understanding (and could easily have been always wrong) that diesel injectors have a constant volume of flow, and the only thing that changes is the duration of the pulsed injection.

 

[dirtworksequip]

Hope i'm wrong, but I can't see where changing the fuel setting would make a whole lot of difference in the operating temp of the engine. I think they need to be looking elsewhere. I've been wrong a million times before though.

 

[radman1]

Radmad; dwmaster, that is an interesting theory, I put 10 hours on the tractor last weekend building a rock wall and every time I got close to the exhaust my eyes would burn like the tractor was running rich, also when I was done for the night and washing down I noticed a lot of soot on the FEL. Hmmmmm, I thought this was an electronically controlled injection system designed to meet the new EPA requirements?

On a positive note the tractor is so much exceeding my expectations of comfort and performance that I have long forgotten the purchase price.

turbo36
Like you I have always thought the exhaust was mildly irritating to my eyes and breathing when near the exhaust or in running in my shed. I have been around various diesels and my previous kubota 3710 never had the irritating exhaust odor. Maybe this is the cure and why the problem seems to be not very common. My tractor seems to have more exhaust smoke than my kubota 3710 and the service manager says he has noticed the smoke as well. The smoke is not excessive but noticable when engine is running cool. I ended up buying the vertical exhaust kit due to the irritating exhaust. Don't notice the exhaust odor as much with the vertical stack. From what my dealer has told me, the poor cab heat seems to be in the 3720's. In the past, I thought the exhaust odor was due to the cool engine and was much less noticable or gone with a hotter engine. Maybe the timing is the problem.

 

[turbo36]

Radman, the fumes from my Bobcat 331 excavator with a Kubota engine seems much more "mild" (for a lack of a better term) I can work around it without any eye irritation.