Poor cab heat

[mike311]

Radman, I just looked on JDParts and noticed your 3720 has an external oil cooler. It is located at the oil filter base. It looks to be plumbed similar to your heater. Next time you run your tractor, get the temp. guage up to 1/4 to 1/3 area, then check and compare the temp. of the oil cooler line and the heater hoses-they should be very close to the same temp. If your oil cooler lines are also cool, I would say you have coolant system problem. If your heater hoses are cooler(both supply and return), your problem is blockage or air in heater core or hoses. With the low temp thermostat and an oil cooler, I don't think your going to see block temps much higher than 125 degrees while running your tractor with no load on it. I would try to check the temp of your radiator hose after your thermostat. It should heat up quickly when the thermostat opens and then very slowly cool when the thermostat closes. It may take 5 to 30 minutes for the thermostat to open the first time- it depends on the load on the engine not so much the RPMs. Your thermostat may be open for very short time(10 to 30 seconds and then close). Now, notice that your return heater hose T's into your lower radiator hose. That is the suction side of your water pump. It is connected there because you need constant circulation for your heater. If it were connected in the upper hose, the coolant would have to travel thru the radiator to get back to the heater. Another reason it is connected there is that when your thermostat is closed, there is no way to circulate coolant thru your radiator. Hope this helps and BTW, heater or no heater, I think you got the best tractor out there! Good Luck Mike

 

[radman1]

Might try taking fan belt off as someone suggested. Then you will know if thermostat is working, guage is working, and if heater will work. I was thinking maybe you have a hose blockage going to heater, but if radiator is not heating up, that's probably not the cause. Is radiator full. We used to have a crown victoria that if coolant got a little low, it wouldn't circulate through heater, but it would still circulate through engine. How many hrs on unit, make them take it back or swap you another unit. Don't know how lemon laws apply to farm equipment.

I went on JD website and typed in thermostat faulty. It appears there are 2 therm. on some applications (12.7 L. engine?). Could this be the problem? Which engine do you have? Might go there and search around for some additional info.

Removing fan belt is an interesting idea. They checked the part number on the thermostat and it was correct. Radiator is full. 24 hours on tractor. Owned 1.5 months.

 

[BTDT]

Which engine do you have? The one they list on website actually has 2 physical thermostats in housing, not just 1 therm. with 2 different part numbers. One is open all the time (for restricted flow I guess, the other closed and opens when temp. calls for it. You may have already searched their website, but they have a search feature where you type in your problem and it gives units and explanations for problems.

Heard from dealer lately?

 

[radman1]

Update. Service manager talked to JD again. Now they are telling him there must be something wrong with my cooling system. They said they tested these tractors in northern Michigan at -10 and they heated fine. Service manager will come out to my place in a few days and try few more ideas. I also suggested putting on a new thermostat. He knows of a couple of other customers with the same complaint. They did put an engine block heater on mine and at least 1 or 2 others when they were new. Air block? JD told him putting in a block heater shouldn't cause an air block in the system. JD told him the temp gauge should get to the half mark even at cold temperatures. Mine reaches about 1/4 - 1/3. I still think the thermostat might be the issue. He said he will also check for kinked hoses, recheck the valve in the cab heater and a few other things. No one else on TBN has this problem which would suggest not a widespread issue.

 

[joe_ferrari]

Is it possible they created another cooling loop path when they put in the engine block heater, ie coolant is circulating thru the block heater instead of the cab heater.

Joe

 

[radman1]

Used tractor again today. Did blade and loader work in 60F temp. Worked tractor hard for about an hour moving dirt. MFWD engaged, spinning tires, hills and so on. Got tractor heat temp gauge to just under half way over. Lots of heat out of the cab heater. Cab heat measured at the seat was 115F with tractor in the shade. It definitely puts out heat if the engine gets warmed up. When I let the tractor idle for 20 minutes the cab heater begins to blow cooler air. A lot of CUT work is certainly not hard work and I shouldn't have to have heavy loads to get heat in the cab. With light duty work the engine just doesn't get hot enough to heat the cab. I feel I should be able to idle the tractor on a 10F day and be warm in the cab.

 

[radman1]

Which engine do you have? The one they list on website actually has 2 physical thermostats in housing, not just 1 therm. with 2 different part numbers. One is open all the time (for restricted flow I guess, the other closed and opens when temp. calls for it. You may have already searched their website, but they have a search feature where you type in your problem and it gives units and explanations for problems.

Heard from dealer lately?

I ask service guy about this possibility. Thanks.

 

[minimax]

Started mine today in 40 F and had hot air in less then 3 mins and thats at 1400 rpm and the heat turned up half way cold air off,engine was to temp in
5 min's.

minimax

 

[radman1]

Started mine today in 40 F and had hot air in less then 3 mins and thats at 1400 rpm and the heat turned up half way cold air off,engine was to temp in
5 min's.

minimax

Your driving me crazy with a cab that works properly. I haven't given up yet. Service guy came to house yesterday but haven't talked with him yet.

 

[radman1]

Service manager from JD just left after checking out tractor. I think we made so important discoveries today. Today was 40F and sunny. Started the tractor. Ran for about 20-30 minutes. Max engine heat at 1400 rpm was 113F measured at the top of the water pump where the heater hose exits. Temp gauge needle on tractor was 3mm off the bottom peg. Cab heat at the vent was 94-97. Ran tractor faster and engine heat raised a couple of degrees.
Next, we clamped off the heater hose return just before the radiator with a vise grip. Engine temp climbed to 146F at the water pump within about 5-10 minutes. (Cab heater temp 51, as expected). Removed the vise grip and watched the engine temp start to drop within 15-20 seconds and after 10-15 minutes back to about 113F.
We both think there is a design flaw in the return of the heater hose. On cars and trucks, the return water from the heater typically enters the engine block directly. JD has the return going to the lower radiator hose near the radiator. The service manager said this is not how it is done on larger ag tractors which have the return directly to the block. We think the return heater hose flow is mixing with and back flowing into the radiator and getting cooled. The returned heater flow is now much cooler than directly going into the engine. The cold heater water now returns to the water pump and is circulated through the engine. The engine now has much cooler water flowing through the engine and can't heat it enough before recirculating back to the cab heater. The flaw seems to be the return from the heater to the lower radiator hose instead of the block. With the cab heater control valve shut off, the engine heater will rise somewhat in temp but not near as high as when the return hose is clamped.
This would explain, why I get good cab heat when working the tractor hard but not when under no load.
Service guy said a customer came in to possibly buy a cab tractor and asked them if JD still has problems with the heater. Customer said he heard this from another dealer. Service guy said they have only sold 3 tractors with cabs. All this summer and fall and all 3 (including me) are complaining about the poor cab heat. Was there a design change or do all 3000 cab series have the heater return hose going to the lower radiator hose?