Removing Underbody Coating?

[Mac Attack]

My daily-driven '92 with ~90k miles is starting to shed wheel well underbody coating bits. Since it's a formula red showing underneath the coating, it looks like crap, especially since I'm still sporting the phat fives and stock suspension (with a large tire/fender gap so you can see everything).

I'm waiting to retire it from the daily grind before I lower it, but in the meantime, I thought I would go ahead and remove as much of the undercoating as possible. There have been a few random posts on this subject, and a few pictures of beautiful wheel wells (John@Microsoft, Kane, and a few others). I don't have the patience to do something that nice, but I at least wanted to get the old crud off.

There seem to be a few methods of removing this stuff after doing internet searching, but none seemed to conclusively work the best (freezing it, blasting it, oven cleaners, fuel oils, and manual scraping). I was a little scared of using the flammable chemicals since I was working in my garage with a gas hot water heater (door was open), but the best method for me was to use PB Blaster and then try to scrape/rub it off. It took me an afternoon, but I managed to remove almost all of that stuff on my drivers side rear. There's a few stubborn spots, and I couldn't get every little bit since I didn't remove the shock, but I took off 1.5 pounds of the stuff (weighed it when finished).

I didn't get to bare aluminum, but my wire brushing in a few small spots went through my red paint and into the white stuff. There shouldn't be any worries with corrosion (I'll paint it black eventually when I do coilovers), and I didn't notice any difference in noise. Why did Honda put this on our cars? Just a little layer of protection from flinging debris?

Anyways, here's a few pictures of my partially finished results. I briefly cleaned the suspension with go-jo (figured that lanolin would be good for my rubbers :smile: ) and a scotchbrite pad:

Dave

 

[davidf]

Looks great. Might I ask what a PB blaster is? I might do this myself. That suspension looks brand new.

 

[john@johnhudakracing]

Nice work.

Cheers,

John

 

[warrenw]

GUNK engine cleaner. let it soak, it will soften, then power wash it thoroghly.

 

[ACCD]

looks great

Has anybody used a soda blaster on the chassis?

http://www.ace-sandblasting.com/soda-blasting-article.html

 

[Synthesis]

Looks great. Might I ask what a PB blaster is? I might do this myself. That suspension looks brand new.

PB Blaster is a penetrating lubricant that can be found at most auto stores. I don't know how well it works for removing this stuff, but it is absolutely awesome to help loosen stuck/rusted bolts. It penetrates into very small areas (getting into threads, etc.), making life easier when disassembling parts.

every garage should have it :wink:

 

[KANE]

Looking good! :smile:

 

[greenberet]

Here in Europe, car restoration shops are increasingly using dry ice blasting to remove undercoating. It supposedly removes undercoating without removing the paint or damaging rubber parts. Maybe that could work for you but unfortunately it's not a DIY.

 

[Mac Attack]

Thanks for the nice comments and the info :smile:

I'll soak some Gunk inside a wheelwell for awhile and then pressure wash it off this weekend. As far as I can tell, PB Blaster, kerosene, and Gunk tend to soften it up a little bit. It then comes off with a little manual labor. The Gunk is cheaper than PB Blaster, so that's what I will probably go with for the other corners. I think I tried every chemical in my garage :biggrin:

I've heard of and like the dry ice idea, but that really isn't too practical for me. That would be the best way, since you make it brittle and then it just flakes off. As long as it's not on a body panel to avoid potential damage (which it obviously isn't), I think this would be the way to go.

ACCD: I would like to have a soda blaster to clean up the aluminum (I think Kane completely stripped all his suspension and did his this way - his pictures are unbelievable). Unfortunately, they are about $500 to purchase a soda blaster, and I don't have any friends with one I could borrow :frown: I've heard of others using media blaster to try and take off undercoating but, from what I've read, it hasn't worked very well.

Dave

 

[DRIFTER]

I have used reducer. It can be purchased at any local paint supply store. I used it to remove some undercoating on some of the aluminum suspension parts and aluminum coolant lines that run down the center of the car then I hit them with fine grit wet sand paper and shined them up to a chrome like finish.:biggrin:

But that was a while ago when I was waiting for my appointment to get my Trans. Rebuilt and I was going threw NSX withdraw and need to do something, so I just started polishing things on the car.:redface:

 

[nsxotic911]

Does ANYTHING work to remove overspray on the suspension pieces..? I have a littl bit of overspray and most of the stuff I have (Gunk Cleaner, PB Plaster..) won't even touch it. :frown:

Do I just need to throw a whole bunch of gasoline on it and remember to not smoke a cigarette in the process?

 

[Mac Attack]

Does ANYTHING work to remove overspray on the suspension pieces..? I have a littl bit of overspray and most of the stuff I have (Gunk Cleaner, PB Plaster..) won't even touch it. :frown:

Do I just need to throw a whole bunch of gasoline on it and remember to not smoke a cigarette in the process?

I had a lot of overspray on my suspension pieces too, but was able to get most off with a plastic scraper or a scotchbrite pad and various chemicals.

I'll have to try the reducer Drifter mentioned above, but I've found that there is a lot of manual work involved even with the use of chemicals. Eastwood makes a spray that supposedly works, but if you go on their forums, a lot of people say it doesn't

 

[DRIFTER]

If you keep the rag good and wet it works well remember to let the chemicals do the work:smile:

 

[ACCD]

Thanks for the nice comments and the info :smile:


ACCD: I would like to have a soda blaster to clean up the aluminum (I think Kane completely stripped all his suspension and did his this way - his pictures are unbelievable). Unfortunately, they are about $500 to purchase a soda blaster, and I don't have any friends with one I could borrow :frown: I've heard of others using media blaster to try and take off undercoating but, from what I've read, it hasn't worked very well.

Dave

Thanks Dave, All I know is I have "shiny" envy. That Aluminum Chassis looks great! I've got a small cabinet bead blaster, and it saves a bunch of time with rusty parts.. I keep wanting to play with the Soda Blaster.. but yup,, $250-$500 is the barrier to entry

I may have to bite-the-bullet and we can ship it around:biggrin:

 

[Mac Attack]

Thanks Dave, All I know is I have "shiny" envy. That Aluminum Chassis looks great! I've got a small cabinet bead blaster, and it saves a bunch of time with rusty parts.. I keep wanting to play with the Soda Blaster.. but yup,, $250-$500 is the barrier to entry

I may have to bite-the-bullet and we can ship it around:biggrin:

This one is the least expensive I could find, but my little 1.5HP air compressor only puts out 6CFM @ 40 psi

http://www.eastwoodco.com/jump.jsp?itemID=1408&itemType=CONTENT&path=32&KickerID=395&KICKER

 

[Mac Attack]

I put on new coilovers and wanted to post a few more pictures and what worked for me on the remaining suspension pieces and wheel wells... This thread gave me incentive for an update:
http://www.nsxprime.com/forums/showthread.php?t=114693


I haven't seen too many threads on cleaning the undercarriage (just a few old posts with dead links and pictures), so I'll point to a nice recent resto by GOLDNSX here:
http://www.nsxprime.com/forums/showthread.php?t=114265



Note - I should have tried the "reducer" as DRIFTER mentioned above but didn't. All of the other chemicals handy in my home did no good just soaking the tar and trying to wire brush or wipe it off. A pressure washer did me no good either. I found the best way for me was a lot of manual labor scraping as much away as possible, and then using chemicals to get the remaining off. This was a PITA and you can count on it taking a FEW FULL DAYS to do all four corners :frown: Lucky I had Thanksgiving break to take the daily beater out of commission for a few days :smile:

1) Order new plastic clips from TYRANSX and then remove fender liners (you should clean them too). To do a good job, you should remove your shocks and loosen brake hose/speed sensor brackets.

2) Using a small, dull, flat-bladed screwdriver, I tried to chip off as much undercoating on the wheel wells as possible. Sometimes I would get lucky and big chunks would flake off, other times I had to scrape as much as possible. As noted, the frame rails and underbody are not smooth so you can't just take a nice scraper and go to town - it's a long painful process getting a little off at a time. I bagged and weighed the scrapings from one of the rear corners - almost two pounds of that crap.

3) After scraping off as much as possible, I then used EasyOff Heavy Duty Oven Cleaner (with Lye). I covered the suspension (don't get this on bare aluminum), put on gloves and a long shirt (not good for your skin), and sprayed this everywhere on the wheel wells. I let it soak for about 10 minutes, then worked it in with a small wire brush. With a bucket of hot water and green ScotchBrite pads, I scrubbed and rinsed everything off. You may need to do this a few times for stubborn areas.

4) Remove suspension covers. The overspray on the suspension pieces are even worse. I used brake cleaner and PB Blaster with a green ScotchBrite pad to get as much as possible off those pieces. Remember to do underneath the pieces too.

At this point, here is a picture of what you should have:

This doesn't look too good, so I sprayed a light coat of black paint on there. You can also go to the auto store and buy an aerosol can of undercoating, but it's easier to remove paint than that stuff so I passed :wink: I don't notice any difference in road noise and debris being kicked up.

The finished product:

 

[goldNSX]

Here in Europe, car restoration shops are increasingly using dry ice blasting to remove undercoating. It supposedly removes undercoating without removing the paint or damaging rubber parts. Maybe that could work for you but unfortunately it's not a DIY.

Yes, I was looking at this option too but they wanted $3k for the whole underbody. Drug store prices...

The black coat dampens the impact of little stones flying off the wheels and around the wheel well.

Nice job!

 

[stuntman]

Yes, I was looking at this option too but they wanted $3k for the whole underbody. Drug store prices...

The black coat dampens the impact of little stones flying off the wheels and around the wheel well.

Nice job!

Have you removed yours? How does it affect the sound of stones hitting around the wheel wells? From tapping the un-coated framerail area of my car it was LOUD. Is it that loud and annoying when rocks get kicked up, or is the framerail (as well as upper wheel well) at an angle where it dosn't hit them dead-on and thus not affecting or increasing the noise from inside the cabin when driving?

-My car is up in the air and i'm cleaning the wheel wells and don't know if I should scrape it all off or not.

 

[goldNSX]

Have you removed yours? How does it affect the sound of stones hitting around the wheel wells? From tapping the un-coated framerail area of my car it was LOUD. Is it that loud and annoying when rocks get kicked up, or is the framerail (as well as upper wheel well) at an angle where it dosn't hit them dead-on and thus not affecting or increasing the noise from inside the cabin when driving?

-My car is up in the air and i'm cleaning the wheel wells and don't know if I should scrape it all off or not.

I've to admit that my point of view was a theoretical one. I don't think that you can hear a difference, not in the NSX. The 'inner protection plastic' takes a lot of energy.

I don't remove mine this winter I think, maybe next. My friend did remove everything but sprayed it with rubber-based stuff, then coated it with body color. Looks good but is a lot of work. Hard to say which way to go. I personally don't like to have the body color on the wheel wells if you can see it with the tires mounted. I even hate the yellow/blue Bilstein's for their color on a red car.

 

[Mac Attack]

Have you removed yours? How does it affect the sound of stones hitting around the wheel wells? From tapping the un-coated framerail area of my car it was LOUD. Is it that loud and annoying when rocks get kicked up, or is the framerail (as well as upper wheel well) at an angle where it dosn't hit them dead-on and thus not affecting or increasing the noise from inside the cabin when driving?

-My car is up in the air and i'm cleaning the wheel wells and don't know if I should scrape it all off or not.

To be honest, I couldn't tell a difference in noise when stones/debris impacted the wheel wells before/after removing the undercoating. What I must be hearing is the debris from the outer part of the rear tires kicking up on the rear spats, since those are pretty pitted.

Your car will be different than mine though - when I have a rear tire mounted, there is less than 3/4" between the inner tire tread and the inner plastic fender liner that would be unprotected if debris flew up there (225 width tire mounted on a 16" phat five with a 1" spacer).

You can always remove it and then spray some back on (available in aerosol cans at your local car parts store) if you can tell a difference. Since it's a lot of work, I recommend removing only the drivers side rear undercoating first as a test :wink:

I took about 8 pounds of wheel well undercoating off (I weighed the stuff I scraped off - anal I know) and replaced it with a thin layer of black paint.

 

[stuntman]

Whew, about an hour of work with a flat head screw driver, chissel, WD40 and i'm almost done cleaning ONE fender. I still have some residual tar stuck in nooks and crannies that I need to scrub out with scotch brite.

I'm on my way, I cleaned and painted a wheel well on another car and it made cleaning MUCH easier and looked way better. My NSX fenderwells (with 120k miles) look like it went rally racing with mud baked onto the sound deadening tar.

...I'm working on it!

 

[Mac Attack]

Brake cleaner or a reducer like DRIFTER recommended will probably be the best to take that stuff off. However, if you're working in closed quarters, you probably don't want to use those.

I found the Heavy Duty Easy Off worked well and had a nice lemon scent :wink: Just don't get it on bare aluminum or your skin.

 

[Tanto2]

3M brake cleaner from NAPA works very well, although even though I don't drive much at all, i can't take raw painted aluminum where rocks can chip the paint off. Paper thin aluminum needs protection IMO!

 

[KANE]

3M brake cleaner from NAPA works very well, although even though I don't drive much at all, i can't take raw painted aluminum where rocks can chip the paint off. Paper thin aluminum needs protection IMO!

Guys I think some of you are failing to grasp the concept:smile: On your nsx right now there are 2 different types of undercoating layered over the top of eachother:

catalyzed undercoating-you dont remove this

non catalyzed undercoating-this is the sticky tar stuff that glues dirt to your undercarriage and is completely unnecessary- This is what you want to remove.

Soda blasting will only work on the suspension castings and arms. On the wheel wells etc, its just going to stick on or bounce off.

You need to use solvents and a scraper / flat screw driverto remove the NON catalyzed undercoating and it will not eat into the catalyzed undercoating.

To be clear you will still have all of the stuff that came from the factory in place even if you remove the sticky petroleum based stuff that is on top of it

Gasoline of kerosene works the best but be really careful. Reducer evaporates to quickly to disolve the tar properly.

Rav

 

[stuntman]

Guys I think some of you are failing to grasp the concept:smile: On your nsx right now there are 2 different types of undercoating layered over the top of eachother:

catalyzed undercoating-you dont remove this

non catalyzed undercoating-this is the sticky tar stuff that glues dirt to your undercarriage and is completely unnecessary- This is what you want to remove.

Soda blasting will only work on the suspension castings and arms. On the wheel wells etc, its just going to stick on or bounce off.

You need to use solvents and a scraper / flat screw driverto remove the NON catalyzed undercoating and it will not eat into the catalyzed undercoating.

To be clear you will still have all of the stuff that came from the factory in place even if you remove the sticky petroleum based stuff that is on top of it

Gasoline of kerosene works the best but be really careful. Reducer evaporates to quickly to disolve the tar properly.

Rav

Just be careful with a screw driver to not jab the fender well too bad, I removed a tiny bit/scraped sime lines into the non-catalyzed undercoating by accident. Some engine enamel should protect it well once its clean and ready for painting.

So you're saying its not a good idea to smoke while using gas to clean the tar off in my garage with the doors closed?