I have an 87 4Runner that I am working on. I bought a vinyl floor kit for it, but before I put it in I am going to spray the floor front to back with Monstaliner. The PO rolled on the cheapo bedliner, so first I am going to strip that back. But I cant decide whether or not to chisel out the factory sound deadener material that is glued to the floor. I have a feeling that this is the cause of some of the rust in these trucks, because it seems to hold water. What is everyone's thoughts on this? This truck is mostly rust free and I would like to keep it that way.

 

I am working on a '85 4Runner and I'm doing the floor also. I would like to leave the factory sound deadener in place but I'm worried that the Monstaliner won't stick to the sound deadener . . . It looks to me like that stuff would be a real nightmare to try and get off the floor.
I see no indication that it is causing any rust in my vehicle. What does a "vinyl floor kit" look like ??

 

Heat gun and some scrapin tools. It's easier if someone did NOT cover it with crappy roll on liner though.

 

I have found the easiest way for me is with a air hammer and a real wide blade I got just for that purpose.

I think what happens is you get condensation between the floor and sound proofing after 10 to 15 years where it breaks loose in places from the floor.