Or should I say something I don't do. I never paint over an older repaint. Here is a photo of an area I sanded showing old laquer based red oxide primer. This and the fact that the repaint could have been an older enamel without hardner is a recipe for disaster. Todays chemically activated primers and paint finishes are designed for HSLA (high strength low alloy) steel. Todays body panels are thinner and harder. Because of this the products need to chemically bond to the steel. In order the give a mechanical bond with new steel you need a 36 grit scratch to create a bond. Anyone old enough to remember the cars that came off the assembly lines in the late 80's will likely remember the paint that was peeling off in sheets. This was due to the altering of the VOC's Volatile Organic Compounds. The sealers and paints flashed too fast and couldn't lock onto the HSLA steel. So the product line was modified to include a bonding action to correct the problem.

So, as a precaustion I never use new product over old repaints. The chemicals that allow these products to lock onto the HSLA steel will eat the old soft paint finishes.

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Also I always strip the cowl vent ribs. Never use a grinder on the cowl top ribs. Notice how nice and round the stamping is? It's easy to grind these things flat and thin. Don't bother using a DA or MA sander either. That just gets the flat part sanded and you end up with a funny looking flat rib. The second issue is the new paint will not stick to the unsanded and likely wax covered sides of the ribs. I use the side edge of a hardened flat blade screw driver and simply scrap the paint off to the metal. This is best done with the fresh air blower removed but you can remove the two bolts from the side brackets and push it down low enough to slip in some masking paper. It's not easy but you can do it. I still need to do the wiper pockets but you get the idea. This is an area that you just can't rush.

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Rick, do you keep your tools in alphabetical order, also. I wish you were my neighbor.

Not intending to highjack but this seems an appropriate thread to add this to. I just started on another 914 this week. I told the owner that these little bubbles all over the car were not a good sign. This is not a high dollar job and he didn't want to strip unless it was absolutely necessary. Once I started sanding the repaint off It became necessary to strip. In the pics you can see the progression as the bubbles got sanded flat, then I broke through to the bare metal. Under each of the bubbles was a small surface rust spot. My guess is the car had been chemically stripped before and was not properly neutralized


These are just two reasons to completely strip. You never know what is lurking under that top coat, or how many coats are lurking under it


Another method for the vent grills is to use a 3" Roloc disc on a 90* pneumatic grinder. It fits really well in the grooves and makes the rounded ends easier to get at

Those sanding marks seem kinda deep. Does the primer fill that to make it smooth or do you sand again with finer paper and then primer or...???

I start at 80 grit. The etching primer, then sealer, then the high build primer will fill in most of that.

I strip with 36 grit because you can reduce your down force and cut the old finish off. Then sand again with 80 before etch primer.

What size & type of sander are you guys using? Pics would be great too.

Yup

For fast work stripping I use an 8" sander. Some guys around here call them a mud hog. I call it a big DA. Otherwise I use a 5" MA I've had for about 25 years.

" Eight inch sander"

Yeah THAT would do the trick!


Now I need to to replace my wimpy 4 inch sander