Heater Core failure

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Nov 15, 2005 | 01:23 PM

fp_5

Thread Starter

Laughing Gas

Joined: Sep 2004

Posts: 1,169

Likes: 4

From: Whitby, Ontario, Canada

Heater Core failure

I replaced my heater core last nite ('76 F100 w/air). I followed the tech. article more or less and things went a lot better than the last time I did it.
Now I did replace the heater core several years ago but I drove the truck very little since then (6k miles). The truck sat for the most part and had anti-freeze in it. Last year around this time I did an engine swap and have been driving the truck daily ever since.
Here's the thing, when I removed the heater core the sides where swelled out on it but it was not corroded. I haven't looked at it real close to find the leak yet but I suspect a seperated joint somewhere. When I was putting things back together I noticed that I had the heater valve (vacuum operated) on the output of the heater core not the input, relative to coolant flow. This means that when the valve was closed the heater core was under pressure. Could this be enough to cause the premature failure of the heater core?
To be on the safe side I moved the valve over to the input hose.

Frank

Nov 15, 2005 | 02:12 PM

ford390gashog

Fleet Owner

Joined: Jan 2004

Posts: 26,007

Likes: 575

From: Brentwood,CA

the valve only stops flow. either way the core is under constant pressure. the heater cores they make today are just crap. ford still sells the original one for about 65.00

Nov 15, 2005 | 02:21 PM

beartracks

Lead Driver

Joined: Nov 2000

Posts: 6,637

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From: Albuquerque

Actually it may be that you were getting surges of pressure. Maybe because of the valve but more likely because of a sticky thermostat or high temperature operation. One side of the core is attatched to suction and the other to pressure at the water pump. Although there may be pressure on the suction side it will be greater on the discharge side.
The same thing can happen to a radiator top tank.

Nov 15, 2005 | 02:51 PM

fp_5

Thread Starter

Laughing Gas

Joined: Sep 2004

Posts: 1,169

Likes: 4

From: Whitby, Ontario, Canada

Thermostat? If anything the truck runs a little to cool. Temperature gauge barely goes past the first line (factory gauge). I kept the big FE rad when I put the 302 in so I expected it to run cool. I had planned on getting a higher temp. thermostat but never got around to it.
I was just curious if placement of the valve or rather incorrect placement of the valve could cause this kind of failure. The entire cooling system is under constant pressure so I didn't think it should of mattered but I'm no expert and I've not seen a swollen core before. I don't remember where I bought the old core, it may have been a cheap one. The one I just put in was from NAPA.

Nov 15, 2005 | 04:24 PM

cigarxtc

Postmaster

Joined: Apr 2000

Posts: 2,881

Likes: 1

From: North of Tulsa, Oklahoma

One thing you might want to take a look at, is the vacuum operated heater hose valve. If it's been in there for a few years you might want to take one side of the hose off and look down the valve body and use your hand to force the side flapper valve up and down. Hopefully you will see the internal valve open and close. Mine worked fine last year. It looked to be the original. I noticed my heat inside the cab was not up to par and discovered that the internal flow hole on that vacuum valve was froze up to about 20-25% open. It wasn't flowing much coolant. I took it out and put straight pipe in on Sunday and can feel a huge difference. Just in time too, we're hitting 40's today and 20's tonight.

Nov 15, 2005 | 05:38 PM

User 71024

Cargo Master

Joined: Sep 2005

Posts: 2,954

Likes: 64

the only thing I have ever seen swell the heater core is Ice, it may have froze. If your pressure cap works, it shouldn't build up enough pressure to hurt the core.

Nov 15, 2005 | 08:03 PM

cheez67

Senior User

Joined: Oct 2005

Posts: 174

Likes: 0

From: brooks a.b.

this may sound really stupid but did you put water into the engine and then and the antifreeze? if so the heater core may have had only water in it for a time.
i know this sounds unreal but i had a customer blow a heater hose in his kenworth about 2 hours from town. he patched the hose filled the rad with water and drove to town to have it fixed right. while driving he had the ac on and it froze his heater core causing it to burst. i wounder if somting like this happened to your heater core.