Heater Problems
New User
Joined: Jun 2002
Posts: 18
Likes: 0
Heater Problems
I have a '79 F250, 351M that has had a heater problem every winter for the last 10 years..Last spring I rebuilt my motor, new radiator, heater core was flow checked, new thermostat, new heater hose, new water pump...still can't get any heat except in the summer. The motor is running up to temp, but it doesn't seem to circulating enough water as the return hose from the core is cold.. I've even switched the hoses..any ideas would be appreciated
Posting Legend
Joined: Sep 2001
Posts: 30,255
Likes: 37
Heater Problems
Does the heater valve work? You say you get heat in the summer, -is it installed backwards so you are closing it in the winter?
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New User
Joined: Jun 2002
Posts: 18
Likes: 0
Heater Problems
>Does the heater valve work? You say you get heat in the
>summer, -is it installed backwards so you are closing it in
>the winter?
>
Yes, I forgot to mention that, I checked it last year and I always leave it on because the cable sticks and its hard to open..thanks for bringing that up, any more ideas, shoot 'em my way,
thanks
>summer, -is it installed backwards so you are closing it in
>the winter?
>
Yes, I forgot to mention that, I checked it last year and I always leave it on because the cable sticks and its hard to open..thanks for bringing that up, any more ideas, shoot 'em my way,
thanks
Senior User
Joined: Mar 2002
Posts: 490
Likes: 1
From: Phx, AZ
Heater Problems
i just had my 400 motor rebuilt by a shop that mainly does ford stuff. the guy told me the 351m and 400 are bad for getting air trapped in the block. he told me when i fill the block leave the heater return hose off of the block next to the thermostat housing. so when the block fills up the air can get out. he aso said to let it sit over night and check it again the next day to see if the level of the water goes down.if need be add more water. and before i pulled the motor my heat didnt work that good either. im gonna get a high volumn water pump to put on my motor i'll let you know how it works out.
Paul
Paul
New User
Joined: Jun 2002
Posts: 18
Likes: 0
Heater Problems
Thanks Paul...
I found out about the air problem by accident. When I first started my new motor, I hooked all the hoses up, fired it up, oil pressure was good, went to listen to the motor for awhile, when I got back inside the truck, I noticed that the motor was extremely hot...I figured out what happened after pulling the thermostat...what a way to break in a new motor
Let me know how that hi-volume pump works out,
Ed
I found out about the air problem by accident. When I first started my new motor, I hooked all the hoses up, fired it up, oil pressure was good, went to listen to the motor for awhile, when I got back inside the truck, I noticed that the motor was extremely hot...I figured out what happened after pulling the thermostat...what a way to break in a new motor
Let me know how that hi-volume pump works out,
Ed
Posting Guru
Joined: Aug 2002
Posts: 1,214
Likes: 2
From: Minneapolis, MN
Heater Problems
Ed,
Have you checked the radiator cap? I've seen some that wouldn't heat very well if the pressure didn't come up.
Just a thought.
Greg
'77 F-250 Camper Special 400ci driver
'76 F-250 Supercab 360ci current project
'71 Mach I 429CJ in storage
'79 F-150 for parts
huct on foniks wurkt fer me
Have you checked the radiator cap? I've seen some that wouldn't heat very well if the pressure didn't come up.
Just a thought.
Greg
'77 F-250 Camper Special 400ci driver
'76 F-250 Supercab 360ci current project
'71 Mach I 429CJ in storage
'79 F-150 for parts
huct on foniks wurkt fer me
Trending Topics
Posting Guru
Joined: Aug 2002
Posts: 1,258
Likes: 0
From: clementsport canada
Heater Problems
our 77 w/351m has always done the same thing....... put a 302 in and it still does it.....
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Lead Driver
Joined: Nov 2000
Posts: 6,620
Likes: 341
From: Albuquerque
Heater Problems
a few notes:
I always drill a 1/16" hole in the thermo to relieve air.
The water valve is supposed to fail open (no vacuum), you can try removing and plugging the vacuum hose.
Of course the lever that controls the air box door has to be in the right position.
I always drill a 1/16" hole in the thermo to relieve air.
The water valve is supposed to fail open (no vacuum), you can try removing and plugging the vacuum hose.
Of course the lever that controls the air box door has to be in the right position.
Posting Guru
Joined: Jul 2001
Posts: 1,613
Likes: 2
From: Gainesville, FL
Heater Problems
All,
Try removing the valve all together.
Go to the Home Depot and buy a female hose splice. Hook it to your Heater hose and connect a garden hose. Turn it on and see what you get. I'll bet there is a bunch of crap caught in there.
Then after you have filled the thing with water hook it back up.
If it doesn't work then, switch your hoses backwards and try again.
If it doesn't work after that, route the exhaust system through the cab of your truck; that should create some heat.
Good Luck,
KingFisher
Try removing the valve all together.
Go to the Home Depot and buy a female hose splice. Hook it to your Heater hose and connect a garden hose. Turn it on and see what you get. I'll bet there is a bunch of crap caught in there.
Then after you have filled the thing with water hook it back up.
If it doesn't work then, switch your hoses backwards and try again.
If it doesn't work after that, route the exhaust system through the cab of your truck; that should create some heat.
Good Luck,
KingFisher
Cargo Master
Joined: Apr 2001
Posts: 2,364
Likes: 3
From: Eustis FL
Heater Problems
I had the same problem for years on my 78 with 351M. All I did to correct it was replace the heater core. It was clogged up too bad to let heat get through it. A flush never helped a whole lot, but this finally cured the problem. Heater cores are cheap. I bought the high output core since it was actually 5 bucks cheaper, but I had to do some sizeable mods to the heater box.
You will have to remove the plenum to do the job, unless you have an a/c equipped truck, in which case you are on your own! LOL
Mark
https://www.ford-trucks.com/user_gallery/displaythumbnail.php?&photoid=5362&.jpg
Ford started it; Ford will finish it!
You will have to remove the plenum to do the job, unless you have an a/c equipped truck, in which case you are on your own! LOL
Mark
https://www.ford-trucks.com/user_gallery/displaythumbnail.php?&photoid=5362&.jpg
Ford started it; Ford will finish it!
New User
Joined: Jun 2002
Posts: 18
Likes: 0
Heater Problems
I'm inclined to beleve the heater core is the problem as well.. I had it out a couple years ago and had it tested at a radiator shop..The high-volume core sounds like the way I'm going to proceed..
Thanks
Thanks
Freshman User
Joined: Oct 2002
Posts: 43
Likes: 0
From: Indiana
Heater Problems
[updated:LAST EDITED ON 08-Nov-02 AT 08:06 PM (EST)]don't know if one exists that would fit the 351m, but once I accidentally installed a reverse-rotation (serpentine) water pump on a 302 that adversly affected my heater, among other things.
