The heater core was mounted straight against the fiberglass body of the heater box. This made me uneasy, feels there should be some sort of vibration absorber there. I would buy one of rubbertherightways kits (see below) if shipping time and cost wasn't infeasible now. Ideas for substitutes? There are a lot EPDM products used for sealing doors and windows in houses. However, most of them have a temperature spec that is way below what is needed. I suspect though it is only the glue that lowers the temperature rating, seems that almost any EPDM product out there otherwise are rated at at least 212F. But it would be suuuuch a major setback if the seal breaks and I have to take this heater apart again, not in the mood for that. Maybe building up my own cushion with RTV?
I have used "sticky" (one side) foam tape "weather-stripping". And apply it to the "box" instead of the firewall, and to the blower housing makes it easier to remove if you have to do pull it apart later. You want one suitable for harsh/wet environments. (rubber/closed cell foam). The 'lighter weight" type will deteriorate.
Aha, no this is for a seal that goes directly on the copper of the heater core. I just tried to boil an EPDM door seal and it really could not even handle 100C. So I ripped out the EPDM I had put around the heater core and cast a cushion using RTV instead. I figure the seal needs to handle at least 110C continually.
Ah! That seal is had no adhesive, it is simply a cushion, and was a very dense rubberized closed cell foam. About 1.5cm (1/2 inch) thick. Here in the US of the A, at car shows and such are vendors selling "knee pads" in different sizes for kneeling or sitting on. Typically about 1/3 meter square, and up to 1 meter square. They are typically 3-4 cm thick. It is similar to Minicell foam used in many insulation applications and is able to withstand up to 200C. (near 400F) and fail at 300C (near 600F) If you have something like that available locally, it will work. Here is a source, https://kayakoutfitting.com/closed-cell-foam-thin-closed-cell-foams-c-15_19/ Or search on eBay in Europe. Hope that helps.
Ahaa interesting! Actually have that material in the garage. Not sure where such thick material would fit in my heating system though. I post a picture instead. Below you see where I tried EPDM, replaced that by RTV now. My idea was to have something there to absorb tension and vibrations in the contact point between the heater core and box.
