Packing Heat

Early Fords, and probably most other old cars, had a very simple heating system where hot coolant continually flows through the heater core. When heat is needed a trap door is opened allowing air to flow through the core and into the cabin. This works great as long as the heater plenum seals are in perfect condition. Otherwise, hot air seeps into the cabin even when the heater is off. On my car the plenum sits under the dash where it acts like a mini radiator, roasting my feet in the Florida heat.

Here's when the hot water from the engine leaves the intake manifold on its way to the heater core.

Here's the heater valve I bought that will let me shut off the flow through the core. It was advertised as having a 5/8" thread. And while it is indeed 5/8", that's not how pipe thread is measured. The old blue elbow is 1/2" npt, while the new part is only 3/8" npt. So I had to make a trip to the hardware store to buy a reducer.

Here's the new heater valve in place. Now my feet will be much happier. If necessary it only takes a few seconds to pop the hood and open the valve.