Heater for M37

[Kenneth Cole]

Hi
I'm wanting to add a heater (coolant style)to my truck and wonder what anyone else has done and if the feel it was large enough (BTU's). Seen them from 12,000 to 30,000 btu's. I live in the mountains by Yellowstone park and it can get a bit nippy.
Thanks for the help
Ken

[Cav Trooper]

Seems to me that the one I bought from Midwest was rated at 30,000 btu, that's close to the size of some small house furnaces. I installed the fender mount style. I found out that the heater intake (fan) will still push air through the ducts even if it's not running since it's pushing air from the fender area into the cab. I left the water valves on and found that I was getting a little warm from the air being forced through the duct. I may put a cable actuated valve, similar to the old Chrysler heater valves, in the line instead of the manual shut off valve at the back of the block. Or, just shut the valves and leave them off until needed. The windshield defroster assembly really limits the view of the speedometer and upper gauges. I think they could have engineered a slimmer assembly to prevent that but, that's just the way it is.
CT

[W_A_Watson_II]

Min's is by no means stock, but the one M I rode in with an in-cab heater sure took up a lot of passenger side floor room. So when I built mine, I used the almost useless storage area under the drivers seat to mount my heater.

As I was mounting bucket seats, the area under the drivers seat was hard to access, and since I was the likely only occupant in cold weather, that area made the best choice, I'd get all the heat.

Selecting a heater for the location was based on sizes, both physical and btu. I ended up with a Heater Craft 401HC Hydronic Heater. (http://www.heatercraft.com).

Technical Specifications/Features

• Amperage: Low 5.3, Med 6.7, High 11.4
• Max. Est. BTU/h: 40,000
• Fits all boats with I/O or In-Board engines
• Grill Size: 8.5" H x 17.5" W
• Air Flow: Low 188 cfm, Med 250 cfm, High 366 cfm.
• Hose barb: 5/8"
• 401-H-C (4H Complete Heater Kit)

It's also available in 24 Volt. I bought it on ebay for US $197.99 from Big Guns Marine Parts Superstore back in December of 2007.

[Charles Talbert]

Call me crazy, most do

Seems to me that the one I bought from Midwest was rated at 30,000 btu, that's close to the size of some small house furnaces. I installed the fender mount style. I found out that the heater intake (fan) will still push air through the ducts even if it's not running since it's pushing air from the fender area into the cab. I left the water valves on and found that I was getting a little warm from the air being forced through the duct. I may put a cable actuated valve, similar to the old Chrysler heater valves, in the line instead of the manual shut off valve at the back of the block. Or, just shut the valves and leave them off until needed. The windshield defroster assembly really limits the view of the speedometer and upper gauges. I think they could have engineered a slimmer assembly to prevent that but, that's just the way it is.
CT

But; cutting off the valves restricting coolant flow through the heater core in the off season will cause leaks in the core when you turn the valves back open next fall. I had this happen several times over the years and asked an old guy that had been in the rad repair business for years why leaks always occurred when you open the valves back up. He just grinned and said that practice brought a good share of his business. He said the core gets use to expanding and contracting from heating and cooling. Then when valves are closed and it sits there with no motion for a few months. When the valves get opened and the heating and cooling starts up again; the stress created by the expansion after a dormant period will cause the core to leak. His advice was stop closing the valves in the summer; I tried it, sure enough, no more leaks.

Putting a valve in line was mentioned, this is fine as the in line valves do not cut the flow off completely. A small amount of coolant still flows, which is enough to keep the problem from happening.

[W_A_Watson_II]

He said the core gets use to expanding and contracting from heating and cooling. Then when valves are closed and it sits there with no motion for a few months. When the valves get opened and the heating and cooling starts up again; the stress created by the expansion after a dormant period will cause the core to leak.

Charles,

Doesn't sound quite right. The continuing to expand and contract should fatigue the metal quicker than giving it a break from the expansion and contraction cycle. I suspect the closing of the valves was causing the problem from stagnate water, and potentially developing trapped air pockets causing corrosion. I've read the solution is to drill a small hole through the valve (s) to let a small amount of water to circulate. This allows for water movement, but at a slow enough rate that you don't experience excessive heat. Now wiht all this said, almost all new vehicles no longer have water flow valves, but this is more related to air blending for climate control, sometime automatically.

[Kenneth Cole]

Thanks for the help guys. I get more help from this site then from the manufacturers. Half the time they don't even respond to my e-mails.
Thanks again.
Ken

[Charles Talbert]

Thanks for the help guys. I get more help from this site then from the manufacturers. Half the time they don't even respond to my e-mails.
Thanks again.
Ken

Something isn't it. Many companies boast of their technical services to customers these days; they just fail to tell you that the phones and computers are staffed mostly by a bunch of know nothings. Not really any need in replying to an email message if you don't have a clue what the sender is asking about anyway.