Scotty76

Fighter pilots, driving my c3 today up rt 4 in Orlando. Very hot in the ****-pit. Is this normal?

Felt under dash and that was where it seemed to be he hottest.

Car was running a tad over 200 deg.

74 LS4-454

Mostly all C3's have the heat problem in the interior. Do a search for interior heat, etc., and you will find many threads and solutions on the problem. Did the insulation on my 82, day & night difference, only problem now is that I have to use my heat in the winter...
With previous C3's owned in the past, it was very rare I would put the heat on in the winter, that is how hot they get when driving.

fishslayer143

it may be the heater shut-off valve ,allowing the hot coolant to flow all the time ...its near firewall on passenger side,in the heater hose

Big Block Dave

Do a search for posts by vettefixr. You may find that the problem area is actually in the footwell of the passenger side, whereas body seams have separated a bit in the air plenum, allowing hot air to enter the system. If you have an exhaust leak, it is substantially worse, as hot exhaust gas is now entering your system.

I have largely eliminated this problem through the guidance of the vettefixr posts. The tricky part is getting your arm in the footwell hole and placing the strip caulk at strategic points inside.

The other tricky part is to make sure that the strip caulk stays put instead of attached to your fingers. May sound gross, but I used spit on my fingers to keep the stuff from staying glued to my fingers.

Also check the firewall where the heater core inlets are, and stuff some foam up in there

Scotty76

The heat was directly under the dash on drivers side. I have the 69 side exhaust kit so it's not coming from the floor pan.

I did turn the heat dial to cool halfway home and it seemed a little better.

Any harm in disconnecting the heater core? I am in Orlando.

gdh

Easier to instal a shutoff valve to bypass the heater core during the warmer months.

Big Block Dave

If the heat is directly under the dash, more than likely it is from a connection within the hvac plumbing that is leaking. You have hot air in the hvac system and it is coming from some where.

The heater core shut off is a great place to start.

Please humor me though...take off the passenger side kick panel and take the car for a long ride. When you get home, open the flapper vent and stick your hand in there with the car running. If you dont feel hot air, then fine. If you do, this is a major contributor

fishslayer143

just replace the bad vac/control shut-off valve with a manual shut-off in the hose ..then you know its off...in warm climates like we live in, you almost never need heat..but if you do, just open the valve