Best way to clean the rear wheel wells for stonguard/painting?

[85RedCarrera]

Man, I have tried everything. I need to be careful, because I am not going to remove all of the old undercoating- I am going to apply more Wurth stonguard over it, where it is in good shape I'll just feather the edges.

So, I don't want to use any chemicals that might get into the old undercoat and affect adhesion of the primer and new undercoat.

WD-40 has always been my go-to for a solvent to remove stuff like this from an aircraft belly, but I'm afraid that it will get into the old undercoating.

What have you guys used (besides bourbon) to keep yourself sane when removing the cooked-on grime ?

Any ideas appreciated!

[Tom F2]

The factory material is probably in fine shape. I suggest that you clean it with Simple Green, a few suitable brushes, and a garden hose, then carefully assess condition of the original, before you think of any refinishing.

[EC900]

Since you’re aware that rear wells tend to collect more oil than fronts, I agree with use of Simple Green or Dawn Heavy Duty cleaners and work well, even tried bbq grille cleaners to break down oil/grease (not very effective). Gunk is messy, smelly and has its own residue to deal with.
Spray SimpleGreen or Dawn on and let it soak a bit, the. work out the dirt in the crevices with a stiff paint brush (cut the bristles down). You’ll probably need to wash/rinse/repeat a couple-few times. Be sure to blow out with compressed air to decrease dry time to inspect how cleaning is going. Power wash after soaking can make quick work - but too close will lift off previously applied aftermarket undercoating.

Over-spraying with fresh Wurth may just “bridge” that old undercoating and bonding might not be adequate even if thoroughly cleaned. Old stuff too brittle?
You may want to try a wipe down with toulene beforehand (Note:Very volatile, open space and mask respirator needed) to pretreat the old undercoating surface a bit may help, really depends on its condition and results will vary. I’ve used denatured alcohol as a prep, and Odorless Mineral spirits may soften up the old undercoating for prep too, evaporates slower but will do good on removing oils too.

My experience: When I got my 911, the wheel wells were caked with decades of dirt, mud, lots of oil saturated mud and the oil film. Looked sloppy and neglected against shiny ArmorAll-ed tires.
I soaked wheel wells with above cleaners, let it set in to soften the dirts, then power washed (rinse) using wide fan spray nozzle and kept a reasonable distance just enough to get the dirt out. Once the bulk of cleaning was done I worked on the details and hard to reach areas. This is tough on jack stands, laying down and splashing water all over. Using a small hand pump sprayer (vs. trigger sprayers) will be useful to dispense cleaners at odd angles. A larger 2 gal. garden sprayer was used to rinse, less splashing.
Oh…and wear goggles !
Since I didn’t have any additional black undercoat ever being used, my original painted undercoat for the most part was perfectly preserved. Not bad for a car that never has wheel wells properly cleaned other than maybe car wash and rain water over 48yrs/200k.
So yes, your original is probably in good shape also if gravel roads weren’t beating them up.

[kltarga72]

As Tom F2 suggest just a good cleaning and flush with water, let dry for a few days before recoating.

[85RedCarrera]

Thanks guys. 40 years of cooked on oil- scraping it was the only thing that made it budge so far. I’ll try Dawn this weekend and may move up to light pressure washing, I’ve got some toluene somewhere, if needed for prep. Appreciate the suggestions!

[A930Rocket]

I used Dawn Heavy Duty cleaner and a small electric pressure washer. With a small pump garden sprayer and the car jacked up and wheels off, it made the inner wheel wells look new.

Looking at it when I started, I don’t think the wheel wells had ever been cleaned.

Back when brake cleaner was a dollar a can, I used to clean everything with that. Now it’s too expensive to even use on the brakes.

[pgeorgeson]

I realize you are looking to DYI it, but I had my undercarriage dry ice blasted and it turned out great. Kept all the original undercoat, but gave it an excellent cleaning I am not sure where you are in NorCal, but the guy I used was in the Roseville area. You can PM me if you want more info.

[85RedCarrera]

Originally Posted by pgeorgeson

I realize you are looking to DYI it, but I had my undercarriage dry ice blasted and it turned out great. Kept all the original undercoat, but gave it an excellent cleaning I am not sure where you are in NorCal, but the guy I used was in the Roseville area. You can PM me if you want more info.

PM Sent.

[speedster911]

For the real tough spots try GROW automotive grease and wax remover. Safe on paint and undercoating and doesn't evaporate as fast as some acetone products. I then follow up with DAWN and a tooth brush.

[Synchro Joe]

[QUOTE=EC900;12546535]Since you’re aware that rear wells tend to collect more oil than fronts, I agree with use of Simple Green or Dawn Heavy Duty cleaners and work well, even tried bbq grille cleaners to break down oil/grease (not very effective). Gunk is messy, smelly and has its own residue to deal with. Spray Simple Green or Dawn on and let it soak a bit, the. work out the dirt in the crevices with a stiff paint brush (cut the bristles down). You’ll probably need to wash/rinse/repeat a couple-few times. Be sure to blow out with compressed air to decrease dry time to inspect how cleaning is going. Power wash after soaking can make quick work - but too close will lift off previously applied aftermarket undercoating.

I agree, this is the best way to do it short of the $$ dry ice cleanings.

[Dpmulvan]

Scotchbrite pads work well.

[PeteKz]

Ive used Simple Green and Gunk Degreaser. Both work--with lots of elbow grease.