Al:
>Their are openings on either end of the box where it mounts to the
>body. Are these to be sealed with foam or something?
There should be a weatherstrip/gasket between the heater box and the body
to prevent air/water from leaking past. It doesn't fill up the entire
space under the box, just the area around the hole (where the box mounts
to the body). My '79 had deteriorated to the point where it just took up
space instead of sealing, so I made a new one out of an old closed-cell
foam pad (I think it used to be an anti-vibration pad for a typewriter),
and sealed it to the body and box with silicone gasket sealer. You may
want to remove the heater box and inspect the gasket. Fortunately, the
boxes on Midgets are much easier to remove and replace than on MGB's.
>I take long trips with the car and live in Florida. While driving
>my feet are so hot they burn. The pedals become hot enough
>to be uncomfortable to touch with bare feet. The water valve to
>the heater box IS off, I am sure. If I open the vents underneath
>extremely hot are rushes in. Any ideas?
The heating system on the Midget is pretty straight forward. The heater
core picks up air drawn through a long 4" diameter hose that has its
inlet located in the grille. The fan pulls in air through this hose,
pushes it through the heater core to heat up the air, and down through
the inlet chamber in the body (top of the transmission hump). The inlet
chamber has a small vent door on either side of the transmission hump in
the footwells; next to these is a small tube fitting with hoses that run
up to the defroster vents.
A dash control runs a flapper door located in the heater box before the
fan (remove the air hose to see it). There are basically three positions
on the heater control: Heat (the flapper door is perpendicular to the
walls of the air hose, the door is fully open), Defrost (the door is
about halfway closed), and Off (the door is fully closed).
To operate the defrost, close the vent doors and turn on the fan. Since
the air can't go through the doors, it will travel up the defrost hoses
and out the defrost vents on the dash (assuming the hose aren't cracked),
and clear your windshield. If your dash control is off, very little air
will be drawn through the tube, and little will come out. Turning it to
the Defrost position limits the amount of colder outside air that the
system has to heat to clear your windscreen. It will still operate in
the Heat position, but will take longer to clear the windshield because
of the amount of colder outside air it has to heat up (you will also move
more air. Conversely, if you open both vent doors, and leave the dash
control to Defrost, the amount of air that flows through the system will
be limited; move it to Heat, and more air can flow through.
The point of all this is to demonstrate that all the heater control does
is limit the amount of air that can travel through the air hose into the
heater core. There is no way to draw fresh air into the vehicle through
the heating system without passing it over the heater core (which heats
it up, naturally).
Your problem is that your feet get hot (been there, don't like it). You
are picking up heat from two sources: radiant heat from the engine,
transmission, and exhaust, and heat leaking past the heater core.
To tone down the radiant heat, insulate the livin' heck out of the floor
and gearbox tunnel, as has been mentioned by others. Commercial material
may be used; I think the jute backed padding with an aluminized surface
will probably work well.
The heat leaking past the heater core can be toned down eliminated by one
of two methods -- bypassing the heater core, or resealing the system to
prevent air leaks. Bypassing the heater core will still allow you open
the vents to introduce some air flow across your feet. Resealing the
system will allow you to fully close the system to prevent any heat from
leaking out and warming your toes. I would recommend that you reseal the
system to prevent air leaks regardless of whether you bypass the heater
core.
Even with the heater valve off, the heater core will still heat up; the
only way to avoid picking up any heat from it is to bypass the core
completely. Remove the short hose that runs from the outlet on the valve
to the heater core inlet, and also remove the hose that runs from the
heater core outlet to the engine -- save these so you replace them later
on if you need/desire to. Run a new length of hose from the heater valve
to the engine (bypassing the heater core). Leave the valve open while in
this configuration to promote coolant circulation.
To reseal the system, start with the air hose in the engine compartment.
Make sure that it is not cracked, broken, etc, and that it fits snugly to
the heater box inlet. This will prevent drawing any hot under-bonnet air
into the system (in other words, you will be drawing only the cooler
outside air). Next, pull the heater box, and seal the fan motor to the
body with silicone, and any seams. Make sure that the flapper door
closes and opens fully, and the rubber seal on the door is in good shape.
Then, install closed-cell foam weatherstripping around the inside of the
back panel of the box on the inside (to seal the panel to the box), and
check the gasket for the box to the body as described above. Moving to
the interior, check that the defroster vent hoses are solid and
uncracked; repair and replace as necessary. Also make sure that the
rubber fitting for the defroster hoses are not leaking, a light coat of
silicone gasket material will cure any sealing problems. Remove the vent
doors, and put some thin closed-cell foam weather stripping around them
to the inside so that they are sealed when closed. Re-install them with
a bit of gasket sealer between the flange and the body.
In short, insulate the footwells, bypass the heater core, and reseal the
system. This will cut down on the radiant heat, and let you open the
vents to let the somewhat cooler outside air flow across your toasted
tootsies.....
Sorry for the length -- Luck!
Rich
Council Bluffs, Iowa
'74.5 RB MGB "Miss Maggie"
'78 Chevy Half-Ton "Waltzin' Matilda" (LBC Support Vehicle)
'79 Midget "Miss Molly"
richard.arnold@juno.com or rdarnold@neonramp.com
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