Sanding Down

[666raCing]

I'm getting rid of the yellow on my mx3 and going with a blackish color.

The guy before me painted the car yellow over the OEM teal/greenish color.

Should i bother sanding it down? If so, what should i do to prepare for the paintjob (i'm having someone else do it)?

[Cy]

if you have access to a random orbital sander...
Goto your favorite store and get 10 of each

80Grit - cuts bondo and Spray bomb(laquer paint turns to a gel when it gets hot from using high grit pads)
100 - cuts multi-layer paint FAST - will goto metal for a joke
180 - cuts multi-layer paint fast - but won't get to the metal as quick
220 - cuts single layers of paint - I use it to prep bare metal for primer
320-optional - on an orbital these are really only for sanding big runs or between primer coats
400-optional- on an orbital these are really only for sanding big runs or between primer coats

*Random orbital is like the paper grit x2 roughly...


Hand sanding a whole car is something I only do after I primer and on the first basecoat and last basecoat before clear..

-320 or 400 primer
-400 basecoat
-Top basecoat:
---if there are runs - 320,400
---if not 400
-2+ days drytime after clear - Wetsand 800(if there's dust, or runs), 1000, 1500, 2000

* For Darker colors and Red 2500 & 3000 wetsand then buff with progressly finer cutting compounds

-Buff buff buff to a super-high gloss...



I was recently introduced to a new dry-sanding system from 3M, based on there hook-it 2 RO sanding attachment line..
Dry sanding up to 2500 and *damp* sanding from 1500-3000.. Plus progressive cut buffing compounds...
They say it will eliminate hairlines from buffing even on high-gloss jet black..

the WHOLE system is like 1500 for all the pads and compounds... but worth it if you paint more then 10 dark color cars a year...

[Yoda]

Test a section on the new paint over the previous and original paint. Something that happened to a friend of mine when the new paint was sprayed over the old paint was a reaction between the to paints causing the old paint to blister. It took close to an extra week to paint the car because the layers of paint had to be stripped and the whole car sanded and prepped again. Re-primed before before the first layer of base coat could be shot.

[monty73741]

my painter friends said what he would do is just spray a sealer over the old paint then repaint the car....

[Cy]

my painter friends said what he would do is just spray a sealer over the old paint then repaint the car....

without even sanding the clear off?????????

[Silkwyrm]

Since you have two paint jobs on there already you need to consider how nice a paint job do you want and if you want it to last a long time. Adding more primer, basecoat and clear at this point is likely to take your paint past 15mils thick. And generally speaking thats not good. Most paint companys will not warranty the paint if the paint layer is that thick. The paint will crack easier at that thickness. If you want a good job and there are no rust spots. Your best bet is to sand off the yellow and sand all the way to the base coat of the teal color. I'd use a dual action sander with 320 or 400 grit till your down to the teal then go over the whole thing with 600. Then the painter can just base and clear it. If theres rust. Well lets just say the above will take a long time and be a lot of work, if theres rust it will be a lot more. I love the MX-3 but I'm not sure its worth the amount of effort your going to have to put into it. If you do it right. If your ok with cutting corners, and spraying over the yellow. It may not be too bad. Just dont have a real nice expensive paint job put on when you got two different paint layers already. You'd be asking for heartache.