Rubber Seal

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custodian

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William
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1973, 1985
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C10
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5.3 LS, 350
I replaced my heater core in my 73 today. I noticed when I replaced the inside heater box that there was a gap between the heater box and defroster duct work. Is there supposed to be a rubber seal between the two? When I removed it, I did not see anything on top the box.

Also, just want to make sure that the 3/4" hose goes to the water pump and the 5/8" hose goes to the intake. I have heat only on this truck.

My truck originally had a 250 6 Cylinder, now has a 357 V8.
 

chengny

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K3500
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Can't tell you for sure, but the parts dwg/list makes no mention of a seal at that joint:

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Also, in my experience (and that of several others), it appears that - for some reason -the gap is there by design. The 81- 91 HVAC systems all have it:

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custodian

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5.3 LS, 350
Thanks for the diagram. I do see a piece that I don't have, the outlet assembly, #14 on the diagram.

What I did for the gap was to put aluminum tape around it.

The heater and defroster works fine now.
 

yevgenievich

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sad
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very sad
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less sad
Mine hase foam filling the gap, tape also works
 

CRM

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Casey
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1985
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K2500
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350 CI
I've wondered the same thing ever since I replaced my heater core. I thought I hadn't put it back together correctly.
 

BiggG74

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Pasco Washington
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Gilbert
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1976
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GMC
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350
I changed my heater core this past fall and it had a material that had a type of insulation on cardboard backing that fit all the way around the box. It tore when I removed it. It got hooked on one of the bolts.


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