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When I start up my '63 Impala every couple of weeks this time of year, to give her some exercise, I sit inside and wait for the engine to warm up for about 5 - 10 minutes. Once that is done I turn on the heater and head down the highway. But, every now and then when the heater fan turns on I'll notice some little dark-colored chunks of foam-like material fall out from under the dash. Does anyone know what that stuff might be? Perhaps some kind of original insulating material hidden from view up under the dash?


Appreciate any thoughts from you folks.


Thanks!
 

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I never looked at the entire width and height of my firewall but there was/is insulation down at the bottom where it is easily visible. Every time I touch it or accidentally nudge it, it basically disintegrates.

I'm not sure why your insulation would only fall when the blower is turned on. I would not think the insulation is in contact with moving parts of the blower.
 

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I never looked at the entire width and height of my firewall but there was/is insulation down at the bottom where it is easily visible. Every time I touch it or accidentally nudge it, it basically disintegrates.

I'm not sure why your insulation would only fall when the blower is turned on. I would not think the insulation is in contact with moving parts of the blower.
The interior of the heater box is pressurized with a quarter horse fan motor; which in turn is pushing any disintegrating open cell foam insulation out from the sealing edges. then gravity takes over and makes it fall down (the bane of all Sci-Fi movies of the fifties in that hot smoke rises and burnt particles and sparks fall in a gravity well with an atmosphere.

The factory used a butyl rubber for sealing, not an open cell foam seal (with an adhesive backing) designed to put a topper on a pick up bed. It sounds to me like some previous owner, or shade tree mechanic, has replaced a corroded water heater core in the past, and used the wrong material to seal it up again after words.

Big Dave
 

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The interior of the heater box is pressurized with a quarter horse fan motor; which in turn is pushing any disintegrating open cell foam insulation out from the sealing edges. then gravity takes over and makes it fall down (the bane of all Sci-Fi movies of the fifties in that hot smoke rises and burnt particles and sparks fall in a gravity well with an atmosphere.

The factory used a butyl rubber for sealing, not an open cell foam seal (with an adhesive backing) designed to put a topper on a pick up bed. It sounds to me like some previous owner, or shade tree mechanic, has replaced a corroded water heater core in the past, and used the wrong material to seal it up again after words.

Big Dave
Thanks, Big Dave!
Your descriptive explanation may have hit it right on the head. I was suspicious of something like that all along. Well, after dealing with it for 9 years now, I won't worry about it since it doesn't seem to be a threat to anything.


Merry Xmas and Happy TRUMP Year, Y'all! :grin2:
 

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And although it may not be the seal from the heater box to the firewall, there is likely a little foam seal that is falling apart inside the heater on the flapper/door that controls the airflow between defrost and floor.

I've had some heater boxes apart where that seal just crumbles.
 
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