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.

 

[CATMAN]

I doubt that changing timing is going to do much for coolant temperature. If they choose to advance the timing, then the engine becomes ever so slightly more efficent, thus to maintain idle rpm(say 700 rpm) the governor tells the fuel injection pump that it requires less fuel delivery to the fuel injection nozzles for that rpm. Less fuel equals less BTUs(heat), BUT by advancing the timing, you give the fuel more overall "time" in the combustion chamber to burn BEFORE the exhaust valve opens and the remaining heat goes out the exhaust system. Allowing this extra overall "time" in the combustion chamber might allow a little addtional heat BUT remember it takes ever so slightly less fuel(BTUs) with advanced timing. Probably no difference. I will say this about advancing the timing within factory guidelines; it does help for white exhaust smoke complaints when engines are first started in colder weather AND it helps reduce that annoying raw diesel fuel smell while the engine is warming up to its operating temperature=if you give the fuel more "time" in the combustion chamber, then it has more time to finish its burning process before it exits out the exhaust system.

One might ask; Why don't diesel engines manufacturers all advance their timing?​

Anytime combustion chambers temperature go above 2500 degrees F, than nitrous oxide is formed, and the EPA requirements/restrictions come into play. Over the years, diesel engine mechanical compression ratios have had to be lowered(high comp ratio=more heat) and injection timing has been steadily becoming more and more retarded from what we had seen on earlier years of the same engine model.(Retarded timing= less "time" in combustion chamber BEFORE the exhaust valve opens and releases that heat and possibly unburn fuel into the exhaust or the turbo)Retarding timing helps control overall combustion temperatures inside the cylinder. Note: It does tend to spin the turbo faster because of the addt'l heat(expanding gases) with retarded timing, but the overall affect is a less efficient engine. You want the most amount of heat to stay in the cylinder to push down on the piston and not go out the exhaust, BUT then keep combustion temperatures below that 2500 degree threashold UNDER ALL OPERATING CONDITIONS as best as possible to pass EPA requirements to sell engines in the USA/Europe. This takes compromises when dealing with a mechanically operated fuel injection system as I see on JD parts for the 3720 tractor. Todays' engineers have it pretty tough to get good fuel economy but must pass EPA quidelines to sell engines. Sorry radman1 for getting long winded and a little off subject, I thought maybe some others might be able to use a little more indepth information on the timing issue.

Personally, I don't have a lot of hope for the timing adjustment, but I would like to see your JD dealer adjust the intake and exhaust valves. If the exhaust valves are too tight, then they open too soon on every cycle and let heat excape out the exhaust system. They will probably tell you that this is considered "preventive maintanence" and the cost to do this is at owner's expense, BUT under your situation, the JD rep may cover the cost. It won't hurt to ask. Note: it would take the valves to be extremely tight to be your one and only cause of this overcooling complaint, so don't get overly excited about this possibilty.​

 

[gemini5362]

When you buy the chips for diesel trucks such as duramax, fords or cummings. One of the things you have to worry about is exhaust temps getting to high. Do those chips not change engine timeing and pulse durations to the injectors along with turbo charger boost. Would that not affect the heat in the engine.

 

[dirtworksequip]

Radman, just a thought. What would you do to fix the problem IF your tractor was not still under warranty? Just curious as to what fix you would come up with?

 

[radman1]

Radman, just a thought. What would you do to fix the problem IF your tractor was not still under warranty? Just curious as to what fix you would come up with?

If I didn't have a block heater, I would directly route the return hose into the engine block on the left. There is a block plug there for the block heater. Unscrew the block plug and put in a fitting for a 5/8" heater hose. I could just remove my block heater and go this route. This would be and easy and hopefully quick fix.
2nd try to find a fitting to fit the opening where the oil filter cooler return water line goes into the water pump. Probably a "T" fitting to allow both the heater return hose and oil filter cooler line to both come into the same port on the water pump. I don't know if such a fitting exists or if there is enough room next to the engine/water pump.
3rd attempt would be to connect the return heater hose closer to the water pump on the radiator hose. The existing fitting could be moved about 6-8" closer to the water pump and thus further from the radiator. NAPA also has a heater hose fitting that can be directly placed into the radiator hose and mount this closer to the water pump - hopefully with in a few inches of the water pump.
4th try would be try to find a temp controlled fan blade clutch. This would require trial and error to find a part that would fit, more labor and cost.

Currently, I am using a vise grip clamped to the return heater hose to shut off the flow. Run the tractor for 10-20 minutes and remove the vise grip. Once everything is warmed up and the thermostat opens to heat the radiator water, I seem able to maintain the heat with the hotter thermostat. However, this works if the temps are in the 20's-30's and may not work if it gets really cold. I haven't tried this with temps below 25.

 

[Kahuna]

It appears you have a problem most do not experience with a cab and have made repeated trys in trying to fix it. Time to trade.

 

[hankus]

I see a lot of diesel vehicles that travel in colder climates, use front covers on their radiators to reduce cooling/maintain heat. I also saw this was the solution for Labrat in his post on 12/04. With the additional cooling capacity that the cab models' heater core provides, I would think that reducing the radiators cooling capacity in this manner would be an accepted practice.

 

[dirtworksequip]

radman, if it makes heat with the return hose clamped with vise grips shouldn't it make heat with the temp control knob set on OFF? I would start by checking that value. Part 31 is a water valve next to the heater core. Has anyone checked it? Are you getting any water flow thru the heater core?

Is there anything I can check out on my 3520/cab that would help you out?

 

[radman1]

radman, if it makes heat with the return hose clamped with vise grips shouldn't it make heat with the temp control knob set on OFF? I would start by checking that value. Part 31 is a water valve next to the heater core. Has anyone checked it? Are you getting any water flow thru the heater core?

Is there anything I can check out on my 3520/cab that would help you out?

From what JD told me, there is always some flow through the heater hose even when the heater valve is turned down all the way. The heater valve has been checked. Once the engine gets hot, the heater puts out more heat than I can handle. That would mean there is definitely flow through the heater core. The problem is getting, and if it gets colder, keeping the engine hot. There is a splice on the incoming heater hose near the cab. I bought a shut off valve to shut off the line so I don't have to pinch off the heater hose with a vise grip. I also figure since there is always flow in the heater hose, I can shut off the heater hose feed line in the summer when it gets warmer. Should help with cooling the cab by not having hot water circulating through the heater hoses. I do this on my 1978 corvette to help with cooling when I changed AC to R134 refrigerant from R12 (freon). R134 is about 20% less efficient than R12.
See my earlier long post with all of the temperature readings. Some of these were with the valve off, on and with the hose clamped off. Hottest engine temps are by far with the heater hose clamped off (170F).

 

[gemini5362]

since you have the valve in there have you tried just turning it so that you reduce the amount of flow through the heater and leaving it at that position all the time. I know the temp control valve does that but if there is water going through the heater core all the time maybe it is too much water even with the valve closed

 

[radman1]

gemini5362
I bought the valve last week but haven't installed it yet. Your idea maybe a good one, although I have tried to partially clamp the hose with a vise grip and it didn't seem to work well. However, the valve will let me do partial closer more precisely.

I got some crazy news today. My JD dealer is going out of business as of Jan 1. My tractor warranty issues will be reassigned to another dealer a little farther away. Employees were notified 1 week ago of closing which surprised all of them. Currently, they have my tractor but haven't changed the injector timing yet. They hope to do it tomorrow, but I figure they may just say forget it and let someone else deal with it. Feel kind of bad for the employees now looking for a job. Now I get to start all over again with someone else.