coolant bypass, how does it work?

sundown57

New member

Equipment
bobcat
Nov 21, 2020
29
3
3
MA
The reason im asking, I just added a cab heater to a D905 engine. I tied one end of the heater into the port in the gooseneck Just under the thermostat. I adapted the other end into the 1-inch hole in the side of the block were the temp sending unit goes. Now I can't get it to warm up more than 100 degrees or so. I do have a Thermostat in it and I did test it, it opens at 160. Did I just create a Huge coolant bypass? If so how should I have hooked it up?
 

bird dogger

Well-known member
Vendor Member

Equipment
Kubota B2650 and lots of other equipment
Feb 24, 2019
1,675
1,579
113
North Dakota
The reason im asking, I just added a cab heater to a D905 engine. I tied one end of the heater into the port in the gooseneck Just under the thermostat. I adapted the other end into the 1-inch hole in the side of the block were the temp sending unit goes. Now I can't get it to warm up more than 100 degrees or so. I do have a Thermostat in it and I did test it, it opens at 160. Did I just create a Huge coolant bypass? If so how should I have hooked it up?
Do you have a small bypass hose (4" to 6" curved hose) located right at the water pump/thermostat housing? I just removed that bypass hose on my B2650 and replaced it with the hoses connected to the heater I added to my cab. Simple and easy. When I remove my cab in the spring, I just replace that short bypass hose for the summertime operation.
 

sundown57

New member

Equipment
bobcat
Nov 21, 2020
29
3
3
MA
I do have that hose, it's 3/8 and my heater is 5/8 I was afraid it would be too small to supply the heater, Maybe if I remove?
 

bird dogger

Well-known member
Vendor Member

Equipment
Kubota B2650 and lots of other equipment
Feb 24, 2019
1,675
1,579
113
North Dakota
I do have that hose, it's 3/8 and my heater is 5/8 I was afraid it would be too small to supply the heater, Maybe if I remove?
Yup, same as mine. I ran the larger hose from the heater to just outside the cab framework. Then with a couple of barbed reducers converted to 3/8" hose for the rest of the way to those bypass fittings. There was plenty of heat supplied to my heater and the smaller 3/8" hose was much easier to run under the hood and up to those bypass fittings. I can't be sure if my heater fittings were 5/8 or 1/2 inch, but either way I think you'd have plenty of heat available to your cab. I'll see if I can find the specs to my heater for you.
David

Edit: Here you go: Kubota B2650 Cab Fabrication | OrangeTractorTalks - Everything Kubota
Starting at post #42 describes the heater I installed. You could google more of the specs to compare it to your heater. You can't see it in the pics but the barbed reducers are just outside the cab wall and hidden behind the loader post. I think the steel barbed reducers were around $4 each, give or take.
Let me know if you want more pics or any other info, but I was more than happy with the heat output through those 3/8 inch hoses. I use my winter fronts on the tractor hood and when the temps drop well below zero, as in -20F and colder, The heater can still have me in shirt sleeves inside the cab.
 
Last edited:

sundown57

New member

Equipment
bobcat
Nov 21, 2020
29
3
3
MA
ok so today i blocked off the bypass hose, Put a shutoff valve in the heater line, and added a 180 thermostat. ran it over an hour and still can't get it over 120 degrees. guess next is to try blocking off the radiator ?