Protecting the underside of a car

jozi

I'm restoring a BMW E30 touring at the min. There's a bit of welding to be done which I have started after that it's time to move onto the underside of the car.

The cars on a spit and completely gutted so access to the underside is as easy as it can be.


The whole underside is covered with a rubbery kind of finish (like shutz or stoneguard). Whats the easiest way of getting this all of? It comes of ok-ish with a wire wheel on the angle grinder but it eventually gets clogged up and still leave a bit of rubber on the under body.

What way do you advice treating the under side once all the rubber is gone?

Plan was to primer it, use seam sealer for all the panel seams and around brackets etc, spray shutz or some kind of under body stone guard and finally waxoil the lot before putting everything back on.

Anyone got experience with certain products, something thats proven to last etc?

Jozi

Captain Slow IRL

What about renting out a sand blasting kit - any decent tool hire place should be able to give you the lot, along with a suitable compressor if you don't have one.

jozi

Not thought about that actually but sounds like a good idea. Aside from blasting, what's involved then after it. Is it just a wipe down or is there more involved in clearing contaminants from blasting?

Also, I've heard sandblasting can be a bit harsh on car body panels and leave waves in the panels :eek: Prob not a concern for the underside as it will be all covered and unseen anyway.

Captain Slow IRL

I'm not sure about the finish but if it's gonna be out of sight, it shouldn't be a concern.

The sand can be messy, so try and do it indoors and put something on the ground to collect as much of the sand as possible, you should be able to put it back in the hopper and reuse it. As for cleaning, there should be no special technique - just try and blow all the sand out of the nooks.

I've no first hand experience of this and am just repeating what someone more experienced at it told me but it all seems straightforward enough. If there's anyone on here that can back up or shoot down my info, go ahead!

Nice project there.

"Rubbery" sounds like stuff used in Mercs of that age. I have heard others removing it by heating with hot air gun and then lifting it off with spatula.

jozi

I've decided against removing it all. I gave the underside a good going over with the powerwasher. Going to just take back the rubbery stuff where it has cracked because of rust under neat it.

Anyone know the right way to re-apply the stuff and if it might react with whats there already?

Captain Slow IRL

What type of product are you applying to it?

jozi

I don't know what to get to do it. There's Shutz and there's 3M stuff you can get. Will waxoil as well when I'm done.

Captain Slow IRL

Paintdoctor would be the man to talk to about this but if you're down to bare metal, you'd probably want to prime and paint it before putting any kind of sealant on it.

I don't think you'd need to use the waxoil if you're using schutz, they're both similiar products, aren't they

jozi

Just noticing who you are on E30 owners

Yeah both do the same job but want to get the best protection possible.

jozi

Slowly getting to the stage where I'm going to have to get some stonechip.

Anyone have any recommendations for a stone chip that dries up like rubber, same as original?

I can get 3 different kinds of this stuff in a local motor factors, Dinitrol (20ish euro), tetra schutz or something and another product, the last 2 being between 3-7 euro.

I don't want to get something thats crap either, I dont want to revisit all the patches in a year or two.

Been thinking I migh give the whole underside a good blast with this once all the patches are covered up. Worried it stay soft and wet though or does it harden?