I know this topic has been discussed numerous times but I'm looking for some fresh answers, I pulled my transmission out for the new one and was planning on undercoating the car before it goes in, there's a few rot holes in the drivers floor pan that I was gonna patch and prime before the undercoating, other than that the underside looks pretty good. I bought two cans of the rustoleum rubberized undercoating but am nervous to put it on after hearing it can trap moisture in and rot without being seen. I'd like to use por15 but don't really have the time to prep for it nor do I want to grind down to bare metal. Has anyone had any good experiences with spray on undercoating?

 

Man I couldnt tell you how much of that stuff Ive used no problems just fix the rust you have and make sure it is clean and dry before you spray on the undercoating

 

You heard correct on the rubber undercoating. You're better off with bed liner.

 

Does it chip off easy or crack?

 

I considered that but I don't want to rip the skin off my hand with one stuck bolt under there lol

 

Can't remember who did it, but fairly sure that it was on a LS swap car, but there was something about using low texture or he strained it before applying it. Either way, speaking from experience, don't use the rubber undercoating. It will not seal out the metal protecting it from rust, it will melt from exhaust heat, instead of scuffing up your hands it will leave a nasty tar-like spot on any skin or clothes. If not bedliner, use something that comes in two parts that you have to mix before applying it.

 

My car was under coated from the dealer when we got it. Not a spot of rust under it 25 years later. Choice is yours.

 

Same here, it's like anything, if you take your time and do it right then it will perform like it's supposed to. Clean and dry surface with a nice even coat and you'll be fine.

 

No it will not I have restored car that are 50 years old with undercoating and it did its job there was no rust now rust dont always start at the bottom of the car it can come from all points and truck bed liner is also good but if you ever need to take it off GOOD LUCK it is as hard as a rock and it will stand up to rock chips just like under coating

and also if you happen to miss sanding a spot undercoating will still stick to the car

 

Thanks for the replies guys, I might just try the front floor pans for now and see how it holds up before I do the rest, can anyone recommend a good spray cleaner to get tranny fluid off the underside, a front seal blew and coated the underside

 

I'm a fan of simple green, spray it on undiluted and let it sit. Spray it again and then start scrubbing it off. In the past I've used the kitchen brushes and scotchbrite pads for the really stubborn stuff.