I'm going to be under sealing my 2003 uk sti.
I plan on sand blasting parts of the underside (lightly)
Then getting it power washed underneath and allowing it to dry for a Number of days.
Any dos or donts?
Anyone recommend a certain sealer, I've used wurth stone guard protection in the past. Would it be worth removing the arch liners to do under them?

Thanks stevie.

 

there was a thread on this recently I was trying to get some ideas on products to use - the consensus was better to strip off all the old crap entirely, dry throughly (heated garage) and then apply specific products for specific areas. Bilt Hamber http://www.bilthamber.com
Seems to get good reviews.

Some of my old cars I've just cleaned/dried and went mad with the waxoyl but I only kept them a few years so can't make comment as to how good the long term protection is.

 

Not really worth trying unless you are going to remove all the parts underneath first.

I wouldn't go shot/sand blasting a complete car... the grit will end up in everything and cause loads of issues. Also shot/sand blasting won't be much good on already undercoated parts. It will be too absorbent and just bounce back. Unless of course you use a very powerful blaster and then you will probably damage things and again it will go everywhere. When people talk about blasting a chassis they mean just a bare metal body not a complete car.

You can try and I wish you the best of luck. But the only proper way to do it is to strip the car and work on a bare chassis. If you are not doing that then that you need to properly powerwash/steam clean underneath and reapply a decent coating. This is not something you can do with DIY/hobby equipment on your back. You need good equipment and the car up on a lift. You also need the ability to completely dry it out before coating or you will cause more rust then just leaving it alone!

The other issue is that if you have rust in seems you can seal the underside as much as you like. Rust will keep coming through it from the inside of damp box sections and areas that have rusted that you can't see like under old soggy seam sealer.

I have personally taken a classic down to the bare chassis and used a angle grinder with steel brush attachment to take the whole underside back to bare metal before painting with epoxy mastic. Trust me it's a very very very long and unpleasent job we are talking weeks of work. My attempts with a diy sand blaster were even more unpleasant and ultimately completely useless.

 

After reading that last post I'd sack it mate