C3 Bypassing a Leaking Heater Core

[Kevin Morris]

My '72s heater core, the lower tube coming through the firewall, has begun leaking. Fortunately, it is leaking into the engine compartment and down the firewall, NOT into the interior! The top hose of my core goes to the bottom of the expansion tank, the top hose from the core goes to the intake (near the thermostat housing). Can anyone tell me how to bypass the heater core, until I can remove and replace it?

Kevin #39927

[Kevin Morris]

Re: C3 Bypassing a Leaking Heater Core

Furthermore, is explacing a heater core on a C3 difficult (realizing that this can be a "relative" question). It appears as though it is removed through the engine compartment, as opposed to from under the dash? It appears that four bolts hold the housing covering the core, fan, fan motor, etc. Once inside this housing, is it difficult to remove the core? Anyone with tips?

Kevin #39927

[Mike M.]

Re: C3 Bypassing a Leaking Heater Core

Remove both hoses from heater core and insert a piece of pipe between the two. The hoses are5/8 and 3/4 so you'll have to jerryrig a piece of pipe to insert between the two(PVC from home depot etc) should be able to provide pieces to construct the pipe with the different O.D.'s. then clamp the two hearer hoses to the fitting. mike

[Joe L.]

Re: C3 Bypassing a Leaking Heater Core

Kevin-----

A C3 heater core is removed from INSIDE the car. To remove it, follow the procedure in you Chevrolet or Corvette Factory Service Manual. In general, you'll need to remove the right side dash pad, perhaps the center cluster, and the heater box. Once the heater box is out of the car, removal of the heater core from the box is quite easy and intuitive. The job is not real difficult, but it is time consuming.

[Shannon Burgess]

Re: C3 Bypassing a Leaking Heater Core

Kevin, assuming your car does not have A/C, it's really easy to remove the core from the engine compartment side. Remove the hoses and disconnect the wires from the blower motor, then remove the nuts on the studs around the perimeter of the blower motor housing. Remove the housing, then remove the "spacer" that is at the end of the heater core. It is the little bolt-in piece that keeps the core snug inside the box. Then gently remove the core from the opening.

Installation is the reverse of removal

[Kevin Morris]

Re: C3 Bypassing a Leaking Heater Core

Thx Shannon and Joe. I think I will try removing it from the engine compartment side, as that looks to be easier to access.

[Kevin Morris]

Re: A Little More Complicated Than That !

Et al,

For those C3 owners needing to replace their heater cores in the future, take note. Joe and Shannon were BOTH right. You must first remove the front half of the heater box (from the engine compartment side). This entails removing the heater hoses, neck of washer bottle, wires from fan motor, relocating a few vacuum hoses, wiper door vacuum actuator, etc. There are about 6 nuts holding the front half of the heater box onto the firewall, plus some black tar-like sealant. My box came right out once the nuts were removed.

The difficulty comes in the fact that, if your car has the original core like mine does, that core was riveted to the bottom of the back half of the heater box (that half that is under the dash). The only way to remove the core from the box is to drill through the rivets from the bottom-side of the box, underneath the dash. Voila, core is out!

Another potential stumbling block is, once you have positioned your new core into the back half of the heater box (that is still under the dash), through the opening in the engine compartment....how do you now secure the core in the box? Only one of the four rivets can be reached from both under the dash AND through the opening in the firewall. Here I used a small nut, bolt, and locking washer. The other three rivet holes can only be reached from the bottom of the box that is under the dash (unless you want to take that half of the box out too....which I did not want to do). On the other three holes, I secured the core by inserting drywall-type anchor screws through the holes in the bottom of the box under the dash, and hence through the holes in the core. I then tightened the screws, expanding the anchors and holding the core in place.

Whew! Sometimes I don't know why I do this to myself....I don't even drive the car in the winter !!

Kevin #39927