Heater Core Replacement on a Series III XJ6

Replacing the heater core on a Series III XJ6 is a real pain. The factory recommends the following procedure:

• 1. Remove the entire interior of the car.
• 2. Disassemble the dash, discharge the A/C system.
• 3. Remove the whole heater & A/C matrix assembly.

This usually takes four days for someone who really knows what they are doing. Fortunately, there's a shortcut!

Take the left console side panel & left under dash panel off. Open the bonnet and remove the heater hoses from the firewall. Using compressed air (carefully), blow the coolant from the lines. Disconnect the steering column at the lower mounting point and remove it from the car. Be careful when unbolting the column mounting brackets, taking note of where the spacers go.

From the inside, carefully cut the heater pipes as close to the steel side panels and the coolant temp sensor as possible, but leave enough pipe to connect heater hoses and clamps to. Remove the side panel from the heater box, being careful to collect the small screws as they come out.

Take the lever rods and electrical connections and remove them from the side of the heater box, taking careful notes and pictures showing where they go back. Slide the heater core out of the heater matrix box. Cut the new heater core pipes in the same places and slide 2 pieces of 9/16" heater hose (2" long) with hose clamps onto the pipes.

Push the new heater core into the heater matrix box and slide the hoses into position. Replace the side panel, rods, electrical connections, etc., then tighten the hose clamps. Reassemble panels and reattach coolant hoses, fill with coolant and pressure test.

This will take about 2-3 hours. Check the tightness of the hose clamps once per year.

If you have any questions, just email us.

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