Official DIY Body work thread
#1
03-21-2009, 01:26 PM
Official DIY Body work thread
These procedures are how I learned to do this work while working about 3 1/2 years at a body shop...
As far as body work goes...
Replacing body panels:
If the panel is a bolt on panel, this is very easy. Simply remove the old panel, put the new on and start each bolt. Then line up the panel making sure all gaps are even and tighten the bolts down. If the panel is glued/welded on, its a good deal more difficult. You might want to have a body shop do this, but if you're feeling optimistic: Find each weld and drill them out. Once all welds are drilled out take an air hammer (if you don't have air tools you can use a hammer and chisle, but painting might be difficult without an air compressor, so I would suggest you get one) and cut away the glue between the two panels. Next, and this involves a couple dozen vice grip pliers, lay the new panel in place and clamp it down with the vise grips. This is just a "test fitting" step. Once you know it fits good (all the gaps are even) take it back off and apply a panel bonding adhesive to all the edges and clamp it back down. Re-weld all the welds. Go over any rough looking edges with body filler (follow the procedure in the filling in dents section) and use seam sealer on all the edges.
Filling in dents:
Start by grinding off the paint at and around the dent. If its a large dent (more than an .125-.25 inch deep), use a stud welder and slide hammer to straighten the metal out the best you can. Next, cut off and grind away all the studs. Next, make sure the area has been grinded with a 36 grit disc before applying body filler, Apply the body filler fairly light coats (it makes it easier to sand) and after each coat, sand it with 80 grit sandpaper on a sanding block. After all body filler is applied and smooth, use a filler primer over the area and after that dries, use a guide coat (I always use lightly dusted coat of cheap black spraypaint) and 320-400 grit wet sandpaper. Keeping the area wet with a spray bottle of water, sand the primer using the guidecoat to find any high or low spots to make sure the panel is perfectly straight. Be sure whenever you are sanding body filler or primer to always use sanding blocks (if you hold the sandpaper in your hand, your fingers will leave grooves in the body filler or primer).
As far as paint work goes...
Getting off the old paint:
This is the most important part of any paint job, because any defects under the paint will show through. If there are any rock chips or cracks in the paint, sand them out making sure you feather out all of the edges (feather them out means that you cannot feel any line). If you're painting with a single stage paint, sand the entire area to be painted with 320-400 grit sandpaper. If you're using a base coat/clear coat paint (base coat is comprised of a specific shade of sealer and the color) and painting the entire panel, also sand the panel with 320-400 grit sandpaper. If you're only fixing a small dent you don't need to lay the base coat over the entire panel, but the entire panel will need to be clear coated. Sand the area to be base coated with 320-400 grit and sand the rest of the panel with 800-1000 grit (clear coat can't fill in any scratches under 800 grit). Once everything is sanded down, pull off any tape and masking paper used and clean the panel with a paint prep spray.
Masking off the panels:
The best way to do this is to back tape all edges (this means put the tape on the inner edges sticky side facing out). Any tape lines on the panel being painted will show and be very ugly. Next, lay the paper across the adjacent panels and stick it to the tape you layed down. Cover the rest of the vehicle in plastic. Once masked off, clean the panels with the paint prep spray on more time to remove any grease from your hands touching the panel. After this wash down, do not touch the panels with your bare hands again.
Spraying the paint:
Make sure the temperature is above 70 deg F. Go over the panel with a tack cloth. If you're using single stage paint, spray 2-3 coats. BETWEEN EACH COAT, wait until the paint is "dry to the touch" before spraying the next coat, and if you see any trash (dirt, bugs, etc) lightly sand them out with 1000 grit sandpaper, Wipe over the panel with the tack cloth again and continue spraying. If you're using base coat/clear coat, you will spray two coats of sealer, two coats of color, and two coats of clear. Follow the same guidelines for inbetween coats.
Important: Don't wax fresh paint for 1-2 months, but rubbing compounds and polish are fine. If the clear coat has an "orange peel" texture to it, wait 12-24 hours and wet-sand the clear coat with 1500 grit sandpaper, dry it off and buff it with a light grit rubbing compound. Buff it again with a swirl mark remover, and then use a polish on it (apply the polish like you would wax).
Anybody else with body work experiece, feel free to correct or add to anything you read (it's been a while so I won't be surprised if I left out something).
As far as body work goes...
Replacing body panels:
If the panel is a bolt on panel, this is very easy. Simply remove the old panel, put the new on and start each bolt. Then line up the panel making sure all gaps are even and tighten the bolts down. If the panel is glued/welded on, its a good deal more difficult. You might want to have a body shop do this, but if you're feeling optimistic: Find each weld and drill them out. Once all welds are drilled out take an air hammer (if you don't have air tools you can use a hammer and chisle, but painting might be difficult without an air compressor, so I would suggest you get one) and cut away the glue between the two panels. Next, and this involves a couple dozen vice grip pliers, lay the new panel in place and clamp it down with the vise grips. This is just a "test fitting" step. Once you know it fits good (all the gaps are even) take it back off and apply a panel bonding adhesive to all the edges and clamp it back down. Re-weld all the welds. Go over any rough looking edges with body filler (follow the procedure in the filling in dents section) and use seam sealer on all the edges.
Filling in dents:
Start by grinding off the paint at and around the dent. If its a large dent (more than an .125-.25 inch deep), use a stud welder and slide hammer to straighten the metal out the best you can. Next, cut off and grind away all the studs. Next, make sure the area has been grinded with a 36 grit disc before applying body filler, Apply the body filler fairly light coats (it makes it easier to sand) and after each coat, sand it with 80 grit sandpaper on a sanding block. After all body filler is applied and smooth, use a filler primer over the area and after that dries, use a guide coat (I always use lightly dusted coat of cheap black spraypaint) and 320-400 grit wet sandpaper. Keeping the area wet with a spray bottle of water, sand the primer using the guidecoat to find any high or low spots to make sure the panel is perfectly straight. Be sure whenever you are sanding body filler or primer to always use sanding blocks (if you hold the sandpaper in your hand, your fingers will leave grooves in the body filler or primer).
As far as paint work goes...
Getting off the old paint:
Sanding... Start by masking off the adjacent panels with tape so you don't accidentally hit them with sandpaper. Next, if you're sanding, start with 80 grit sandpaper and go down to bare metal, then step up to finer grits to get out the scratches (paint will not fill in anything under 320 grit sand scratches, and you will see them through the paint). Use 120 to sand out the 80 grit scratches, then use 180 on the 120 grit scratches, then use 220 on the 180 grit scratches, and finally use 320 to get out the 220 scratches.
Chemical Stripping... Use a chemical stripper like Aircraft Paint stripper. VERY IMPORTANT: WEAR GLOVES BECAUSE THE PAINT STRIPPER WILL BURN YOU! Start by masking off about a .25-.50 inch in from the edges of the panel(s) you're working on to prevent getting the paint stripper in the gaps (example... if you're working on a door, mask off the edges so the paint stripper doesn't get in the door jamb and eat the paint in there). Next, for the best results, run over the panel(s) with 80 grit sandpaper to roughen up the paint, and then coat the panel in paint stripper. Let it work for 30 minutes to 1 hour. Come back and scrape the paint off with a straight razor blade. Repeat until all the paint is removed and bare metal is exposed. Next, wash off all the excess paint stripper... this is very very important, because any remaining paint stripper will eat through whatever you try to lay on top of it. Next, sand the metal with 180-320 grit sandpaper like described above.
Prepping:Chemical Stripping... Use a chemical stripper like Aircraft Paint stripper. VERY IMPORTANT: WEAR GLOVES BECAUSE THE PAINT STRIPPER WILL BURN YOU! Start by masking off about a .25-.50 inch in from the edges of the panel(s) you're working on to prevent getting the paint stripper in the gaps (example... if you're working on a door, mask off the edges so the paint stripper doesn't get in the door jamb and eat the paint in there). Next, for the best results, run over the panel(s) with 80 grit sandpaper to roughen up the paint, and then coat the panel in paint stripper. Let it work for 30 minutes to 1 hour. Come back and scrape the paint off with a straight razor blade. Repeat until all the paint is removed and bare metal is exposed. Next, wash off all the excess paint stripper... this is very very important, because any remaining paint stripper will eat through whatever you try to lay on top of it. Next, sand the metal with 180-320 grit sandpaper like described above.
This is the most important part of any paint job, because any defects under the paint will show through. If there are any rock chips or cracks in the paint, sand them out making sure you feather out all of the edges (feather them out means that you cannot feel any line). If you're painting with a single stage paint, sand the entire area to be painted with 320-400 grit sandpaper. If you're using a base coat/clear coat paint (base coat is comprised of a specific shade of sealer and the color) and painting the entire panel, also sand the panel with 320-400 grit sandpaper. If you're only fixing a small dent you don't need to lay the base coat over the entire panel, but the entire panel will need to be clear coated. Sand the area to be base coated with 320-400 grit and sand the rest of the panel with 800-1000 grit (clear coat can't fill in any scratches under 800 grit). Once everything is sanded down, pull off any tape and masking paper used and clean the panel with a paint prep spray.
Masking off the panels:
The best way to do this is to back tape all edges (this means put the tape on the inner edges sticky side facing out). Any tape lines on the panel being painted will show and be very ugly. Next, lay the paper across the adjacent panels and stick it to the tape you layed down. Cover the rest of the vehicle in plastic. Once masked off, clean the panels with the paint prep spray on more time to remove any grease from your hands touching the panel. After this wash down, do not touch the panels with your bare hands again.
Spraying the paint:
Make sure the temperature is above 70 deg F. Go over the panel with a tack cloth. If you're using single stage paint, spray 2-3 coats. BETWEEN EACH COAT, wait until the paint is "dry to the touch" before spraying the next coat, and if you see any trash (dirt, bugs, etc) lightly sand them out with 1000 grit sandpaper, Wipe over the panel with the tack cloth again and continue spraying. If you're using base coat/clear coat, you will spray two coats of sealer, two coats of color, and two coats of clear. Follow the same guidelines for inbetween coats.
Important: Don't wax fresh paint for 1-2 months, but rubbing compounds and polish are fine. If the clear coat has an "orange peel" texture to it, wait 12-24 hours and wet-sand the clear coat with 1500 grit sandpaper, dry it off and buff it with a light grit rubbing compound. Buff it again with a swirl mark remover, and then use a polish on it (apply the polish like you would wax).
Anybody else with body work experiece, feel free to correct or add to anything you read (it's been a while so I won't be surprised if I left out something).
Last edited by 95_318SLT; 03-22-2009 at 03:00 AM.
#5
03-23-2009, 12:15 PM
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#6
03-23-2009, 04:28 PM
If its surface rust, like bigkat91 said, just grind it out, and then follow the guidlines I mentioned above for getting out the griding scratches (the part about using progressively finer grit sandpaper). Once the rust is gone and the metal has 320 grit scratches in it use 3-4 coats of filler primer over the area and block it with 320-400 grit sandpaper. If the rust has gone through, you'll need to either make patch panels and weld them in or replace the entire body panel. Make sure when you fix the rust that you properly seal it from the back side of the panel (repainting it should take care of sealing it from the front)
Last edited by 95_318SLT; 03-23-2009 at 05:09 PM.
