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79 Heat issue

LEB Ben

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Hey fellas...cranked on the heat today in my 79 Bronco for the first time in a year, and much to my dismay had a slight issue. While parked, the heat came out on the floor like it should. However, the more gas I would give it during acceleration, the more the heat would switch from the floor to defrosters...and as I came back down to idle, the more it would go back to the floor. While cruising at speed, it's a 50/50 split. I'm thinking it's a matter of tracking down a vacuum issue. Thoughts?
 

LEB Ben

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Check for mouse or other critter nests at the blend door.

No blockages

I think your correct on the vacuum

Do you think the symptoms would be a result of a loose/cracked/busted hose? Any ideas if it would be interior or exterior hoses being problematic?
 

LEB Ben

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LEB Ben

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The can is a reservoir to maintain a prescribed vacuum level to prevent The very same symptoms that you are experiencing.


So if it were leaking, then it would possibly cause those symptoms, correct? Which in all honesty is a possibility, somewhere during the engine swap, it got crunched...no noticeable holes, but it's creased horizontally right in the middle. IIRC, my grandfather used to cut the ends of a bad can then weld them to a coffee can.
 

blacksnapon

Moderator
Staff member
Time for the salvage yard! You don't necessarily need a can, other manufacturers have plastic ones. Just keep your eyes open.
 

LEB Ben

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Alright so a quick checklist:

1) coffee can
2) interior vacuum lines (should be 1 or 2 lines right behind dash, right?)
3) exterior vacuum lines
 
I am by no means a mech. but most times I've had vacuum problems it turned out to be at the source. The vacuum off the carb is usually clogged with oil condesation residue.

Idid stay at a Holiday Inn Express , last year
 

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