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Firewall insulation on my Mazda 3

At my 30,000 mile service it was discovered that rodents had eaten away much of the firewall insulation in front of the passenger side of the engine compartment. Of course the dealer wants to fix it which would require removing the engine. My question is, how necessary is this insulation? I haven’t noticed not having it. Is it a safety concern or does it just protect against heat/noise being transferred from the engine compartment into the vehicle? Thanks for any help!

It’s called a Firewall to protect you from engine fires, which were quite common in the early days of automobiles. Its present function is the same and the insulation provides excessive heat from coming into the passenger compartment, as well as helping the A/C perform better. An additional function is sound deadener.

Would I remove the engine just to replace it? No, but if the additional noise bothers you I would sell the car. Don’t be tempted to spray polyurethane foam there; it is flammable.

I would not fix it. You may notice more noise in the cabin from the engine though.


Unless the shop is doing this repair on their dime, pass on it.