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m939 Heater Core

Retiredwarhorses

Well-known member
Steel Soldiers Supporter
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Location
Brentwood, Calif
Lost my core today as well....15min drive and now a few hours of work...
gonna take it to the radiator shop...unless anyone has a good take out for sale...
stupid design, all they had to do was make the left bracket removable.
i know the entire support bracket can come off, but instead of welding the support back on one side it would have made maint easy just make it attach with a bolt on the fire wall and one on the forward end.
 
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plode

Member
270
3
18
Location
South Jersey
I got mine in on Tuesday and it works fine. I will have to redo my grounding when it isn't 10 degrees out but I'm happy to at least have heat. I think I might have to cover up a bit of the front of the hood though it takes absolutely forever for the engine to get to temp running it as-is. I should say for whatever reason the fan assembly on mine was completely seized on the shaft of the old motor and I ended up having to pop it into the drill press and bore the shaft out to get it off. It mated up to the new motor just fine though.

EDIT: Disregard this for now. I found I had an old bilge exhaust blower, brand new, for a boat project that never got started. It is 24v too. So I just took it apart, removed the motor and blower wheel, and sure enough it's 4.5". And the blower motor bolted up perfectly to the trucks adapter plate...so I bolted it on. I fired it up on 12v..Can't tell if the now loose clearances(4.5" as opposed to 4-5/8"-4-3/4") will cause it to not blow hard enough to circulate air into the truck, but it's worth a shot for now.

Old post:
Sorry to revive an old thread, but this is exactly the situation I'm in.
Mine is 100% siezed to the shaft, and the vanes are pretty much destroyed. I sprayed it with PB blaster, heated it, beat it, it doesn't want to budge. Looks like the military might have dropped a tool into it, and then turned it on.
I have the new blower motor coming on Thursday, does anyone know where to get a replacement fan assembly(or part numbers)?

The part number from the TM isn't bringing much of anything up for me.
The blower wheel is somewhere between 4 5/8"- 4 3/4"...hard for me to tell since it's all bent up.
 
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Wildchild467

Well-known member
Steel Soldiers Supporter
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Location
Milford / Michigan
I found one that fits the heater box, but I had to make a new cover. Murray #398010 $20.00 View attachment 472427View attachment 472428View attachment 472429

Any updates a year later to say how this heater core is working? Is this core better heat than the original core? How did you prevent air from coming out of where the heater lines go in. A buddy of mine wants to put in this core and move the heater box inside. All along I think the heater core is just partly clogged inside. He replaced the radiator about a year ago and found that was scaled up inside. So his heater core must be similar even it seems to flow ok. My vote to fix his heater is a winter front cover and replace the heater core with an OEM one. His complaint now is that his heater does not work good in the cab and cools off after going down the road. It seems like it would be so much faster just changing the core to a original core. What do you guys think? I'm not a purist but it seems like the OEM heat in the M939A2's would work fine when it is 14 degrees out, shouldn't it? Maybe I am wrong and this heater core is a huge improvement over a good working stock heater core?
 
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jarhead1086

Member
112
2
16
Location
Farr West, UT
I am also tempted to move a heater core and a blower under the dash. I don't want anything that close to the turbo I added. The stock design is very bulky. Mine was working when I removed it, but it was full of fine dust and the hamster wheel had unnecessary drag from it. This great thread gave me all the performance numbers I was looking for while searching for a replacement. The flapper just collects dust on the horizontal surface and then dumps it in when you open it up. If the motor starts getting tired while mounted in the cab you will have a better chance of hearing it. Outside air and cab air is nearly the same even with my hardtop as far as where the blower is sucking from. Need some fresh weather strip one of these days.
 

joesco

Member
442
1
18
Location
Hampstead, NH
My heater core started leaking in the front, dripping / streaming antifreeze on my exhaust manifold. Found it much easier to remove the entire heater assembly as the Philips screws on the cover were very difficult to remove. I believe vibration and its loose installation caused it to fail. At a radiator shop now, $140.00 repair. Rubber weatherstripping will be a must!
 

juanprado

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Metairie/La (N'awlins)
My heater core started leaking in the front, dripping / streaming antifreeze on my exhaust manifold. Found it much easier to remove the entire heater assembly as the Philips screws on the cover were very difficult to remove. I believe vibration and its loose installation caused it to fail. At a radiator shop now, $140.00 repair. Rubber weatherstripping will be a must!
For that much coin, a new one is just a little more.
 

juanprado

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Metairie/La (N'awlins)
contact info was accurate at the time I posted. They are crazy priced though.

If you want OE, then just bring yours to a competent radiator shop to fix. Best bet in my opinion.
 

therooster2001

Active member
824
44
28
Location
Colorado
Mine has a bad core. Isn't a "cheap" fix like most of them. 175 isn't that bad IMO
$175 is pretty expensive I think. I got told the same thing (and I keep wondering if I was being taken) so I grabbed one from the salvage yard in KS, not too far from you. I bet he'd give you two for 1/4 of that. Not guaranteed to be leakproof. I reinstalled mine this fall and it worked wonderful. Grabbed a spare just in case!
 
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