I was talking to Norm about my current rust woes, and indicated to him that I really should just strip away all the rubbery black undercoating on my car and inspect the metal before re-coating.

Norm suggested the use of an angle grinder fitted with some sort of wire wheel or brush - has anyone else used this technique and tools? If so, any tips? Can I do that maintenance with the car on stands, or is a proper lift a minimum requirement?

I've sort of been pondering buying an angle grinder for other reasons, so I'll probably end up with one eventually... I've never seen a wire brush setup for it though - won't the underbody gunk just clog the wheel?

 

I would scrape as much of the undercoating off with a putty knife as possible. I use one of the stiff type and sharpen the one end like a knife.

I used a 4" 36 grit paper disc and for the tight spots I use a angle die grinder with 2" roloc discs also 36 grit. Yes they clog but I just get a cheapo screw driver and one quick pass across the disk with the screw driver and they come clean.

I found that the wire wheel takes too long to remove the thicker stuff. You can just buy a 3" or 4" wire wheel that screws right onto the grinder. I have an 4" air grinder that has different threads than the standard 4.5" electric grinders do but they sell an adapter. Lowes or home depot normally has everything you need.

I would get the twisted wire wheel and not the straight wires because the straight ones really aren't abrasive enough.

And one side note wear a hat when you do it because that rubber melts and flies and won't come out of hair.

 

To your other question I used jack stand and a creeper to work on mine. You will need a long framed jack to get it high enough to get underneath though. You can also try to jack it up a little, put the stands in the low position, then put a block on the jack and then raise it some more. I was just lifting a stripped body with the small jack and blocks and it was pretty scary. I don't recommend this method.

I got a long framed jack from harbor freight for 120 bucks, and for as much as you'll need it, it's good enough.

 

also wear a face shield....i've had the wires on a wire brush come flyin off before and they were stuck in my shirt.......

 

Jeez... now I'm afraid...

 

It's a messy job for sure, and definitely not one of the more fun projects.

Undercoating wouldn't be doing its job if it wasn't a pain to remove.

The loose wires from the brush aren't that big of a deal, it mainly happens when the wire brush starts to get worn out. If you get one that has the twisted wires it's less of a problem. You just don't really want an airborne wire or a hot piece of rubber stuck in your eye so wear some shades when you grind.

Alternatively you could sand/media blast the bottom or maybe even some sort of chemical stripper might do the job. I don't recommend sand blasting in the garage though, my garage door doesn't work too well anymore.

 

I did mine in the garage on jack stands....here's some 'after action, lessons learned'

• All the suggested methods work....if you do this by hand working on your back it is VERY labor intensive and a mess. You can save a lot of time if willing to spend a few bucks by looking into media blasting....even a high pressure steam clean can really help.
• If the coating is 'soft' go at it with a scraper first. I found that after a scrape most residual could be removed by wiping down with a rag and mineral spirits; mine was still pretty soft. Eastwood also has a specific remover, their item 31130Z. If you go chemical be aware of fumes. If your furnace or hot water heater are in the garage you could blow the whole place up....ventilate!
• The dust from grinding, or the fumes from a chemical really call for a respirator in addition to good eye/face protection. I've gotten myself sick more than once by neglecting this part. 3M is the industry standard but b sure to have the correct filter for the job....particulate and organic vapor are different filter kits (easily interchanged) EASTWOOD has this, so does HD and LOWES.
• Wearing all this crap AND working in a limited space makes that media blast look real good! But if you are not in a hurry, have fun!
• The down side of a grinder/wire cup/media blast or other mechanical process is the ease with which you can remove more good metal than you intended. With media blasting in a shop, they can use a softer material then sand and (probably) have fewer blow thrus...

Lastly - be in the right frame of mind. Odds are you are gonna have a few spots.....maybe more than a few.... I sure do!

 

What does a blast job normally go for? I'd certainly not be adverse to someone ELSE doing the work this time, but I'm trying to save $ where I can to actually REPAIR things I find, as well as purchase replacement undercoating.

Thanks, guys!

 

material from the interior of my BMW (beneath the seats and in the trunk) by using a heat lamp to first soften the gummy stuff then quickly use a putty knife (a plastic paint scraper will work too) to scrap down to bare metal. Now, I can't be certain that this method will work on the rustproofing gunk, but I believe the same theory applies. Any remaining residue usually comes off with a liberal application of carburator cleaning and a rag. Be sure to remove the heat lamp prior to utilization of the carburator cleaner, though. Also ensure that you're working in a well ventilated space. Good luck....

Jeff

 

One time i had one get stuck in my shoulder about 1/4 inch deep. hurt like a b**** but at least it wasnt in my eye.

 

EYE PROTECTION.....

Guy I bought my Mini from was tinkering b4 I bought it....had the speedo cable off.....while trying to replace it, it 'popped' and caught him in the eye...1 in 1,000,000 shot. Scratched Cornea ..... ouch.

Safety glasses under $5.....and up. I have 4 pair on my work bench.....some are better for some things..... And then there's the face shield and the welding helmet. But I kick myself if I find I was neglegent....in my 'job' I spent a lot of time walking around and 'slappin' folks about PPE!

 

i was wearin eye protection. my dad lost most of his vision in his right eye from a chizel shooting into his glasses at high speed off of a lathe. he was wearing safety goggles too, but they just got pushed back and broke his normal glasses. goggles help, but only to a point.

 

Try a heat gun used for paint stripping to soften it then a stiff putty knife to remove the better part of it.

 

I have a feeling that this will still leave little streaks of black everywhere.