911 SC heater box replacement,any tips for the job?
The heater boxes on my SC are rusted through and the heat exchangers are leaking exhaust into the cabin. I know this is one of the bigger jobs on an air-cooled 911 since they're part of the exhaust system. Has anyone done this at home or is it strictly a specialist job? Budget-wise I'm looking at $1,500 for the parts alone, so if I can save on labour that would help.
It's doable at home but it's a full day job and you need a pit or a good set of ramps. The heater boxes bolt to the exhaust manifold and the muffler, and everything is held together with high-temperature fasteners that are usually corroded solid. Penetrating oil for a week before you start helps enormously. SSI stainless steel heater boxes are about $1,200 for the pair and they'll outlast the car. The factory steel ones will just rust again in five to ten years. Make sure you replace the control cables and flap valves at the same time.
The exhaust fumes in the cabin issue is actually a safety concern, not just a comfort one. Carbon monoxide from a leaking heat exchanger is genuinely dangerous. I'd prioritise this job above all else. On the E-Type the exhaust-based cabin heating system has the same failure mode and it's something we take very seriously in the Jaguar community.