I am about to remove my engine rear and front suspension drivetrain and i wanted to know about if i should undercoat the car while it is so empty i am going to paint the car inside and out and engine bay so thought i would be logical to do a underbody treatment. i can borrow a friends sandblaster so i could use that but i wanted to know if i should epoxy coat it, do a bed linner type coating or what? i know it adds weight but it should be done right. Now i am also installing se susp. and wanted to clean the diff. and wanted to know what should be done before installing it? i flushed my old fc with Diesel fuel and that seemed to flush it out well but i know kerosene is suppose to help with this as well anyone know more? thanks for your time.

 

I have use an "asphaltic undercoating" that is not rubbery and stays on forever. I am now freshening up over that with the bedliner rattle can stuff that isn't as thick, but has great adhesion and looks great.

I'd advise just to stay away from the heavy rubberised crap that is most common on the shelves of the auto parts stores.

 

3m undercoating works really well, just make sure you clean the surface very very well first, and if theres any rust at all don't undercoat over it, grind it off or treat it some other way, the undercoating doesn't stop existing rust, it will just cover it and allow it to keep eating away at your car. On my project car I sandblasted almost the whole underside of the car, sealed it all up with por 15, then topped that with primer and then the 3m undercoating. Seemed to work quite well. I don't believe por 15's claim of being able to go right over rust (and have it last that is) but it does do a nice job of sealing up exposed metal. Rather than buy the official por15 brand primer I just use rustolium primer, applied to the por15 while its still tacky (as per the por15 instrustions) that makes a real good bond. good luck

 

If you build a house, you start with the foundation, not the roofing and siding, same for a car. If the underbody won't outlast the paint job job, fix it, or don't paint at all.

Simple answer, yes, do first and as soon as possible, less work and expense.