minor rust/ interior question- newbie qs.

[SwissEd]

My Fj40 (CA truck now in Switz) has OEM mats which look a bit tired. As I only use the truck during the summer with bikini I noticed some rust in driver's side foot area under mat. The factory installed (I think) asphalt paper (like plastic roofing cement) had some rust penetrating. I started chipping away which turned out to be a half day tedious job to get the "flaky" bits off to bare metal. Now about half the area in foot well is to bare metal (with some surface rust) and a hole the size of a dime (not drain hole) and the remaining area with well attached black roofing like cement. I used a heat gun in the end to feather the transition. I have heard from a friend best to strip the whole thing, remove mats and paint and drive like that so no water gets trapped. My questions are:
1. should I try to remove all the black 'tar' (the passenger side has no rust) and the large pieces under the seat would be a chore to remove?
2. should I grind rust off and use some rust preparation (don't know what they have in Switz.) and then coat area with roofing cement and cover with mat (f it gets wet take out mat to dry)?
3. I see mats costing $500 for new Australian ones- ouch, any decent grey alternatives?
4. Any other suggestions?
Truck looks great otherwise and is a 'keeper' so I want to do it right.
Many thanks and since I am going to be in CA in August so I could bring stuff back here like mats.
Ed
PS I can add photos if that helps.

 

[Michael Hanson]

I would cut out the rust and weld in new metal,prime ,paint put down dura-mat and throw in the mats and drive it. 2 cents Mike

 

[dargreg]

I would cut out the rust and weld in new metal,prime ,paint put down dura-mat and throw in the mats and drive it. 2 cents Mike

x2 Paint it with POR 15

 

[SwissEd]

What would you do with the remaining part of asphalt like tar that I did not chip away and appears to have NO rust underneat? Would you prep, paint with POR 15 (just found out it exists thankfully in Europe) and THEN put more black plastic roofing cement down or leave it?

Thanks,
Ed

 

[numby]

I think the heavy tar mainly acts as a noise barrier. You could leave it on the firewall beneath the pedals but I would remove it from the floors beneath the seats, etc. so that it doesn't trap any more water. Don't bother using roofing tar or rubberized undercoating - at least not on the inside. I'd use a layer of seam sealer before either of those options. Fix holes, strip, and paint (repeat often) or use a more durable coating like POR-15. Then remember to knock the snow off your boots in winter before getting in. Rust seems to be more common on the driver side floor. I wonder why?

 

[dargreg]

Or chip the liner away around the edges to bare metal then paint with POR15.I,ve had a lot of rusted out floor panels where the only good metal was under the liner.

 

[Gusb]

Where it's easily pulled up, there's usually rust that needs repair. Where it's still stuck hard in place the steel is probably still clean. Opposite of stripping paint, where the rust will tend "hold" the paint (using a chemical stripper).