clear coat checking, sand to bare metal ?

[diy83sc]

The car is an 80 SC in, Weissach, Black Metallic. The clear coat is checking, failing, chipped in some spots. Should I assume the original paint is failing as well? I am going to have the car re-sprayed same color, door jamb blend.

How to know when to go to bare metal or how much sand off to get at a good base?

The side panel clear coat is in generally good shape, less direct sun, but still needs to come down to fix the dings and scratches. I'll attempt to take some pictures with daylight in the morning of the top panels. Looks just like the pictures of the van...

--> This is what happens when you search AFTER a post. I think I have my answer here. Welcome input jsut the same.

http://forums.pelicanparts.com/paint-bodywork-discussion-forum/887871-dont-do.html

[GotaT]

Typically if just the clear is flaking off or dull, and the base coat is holding well, you can scuff the panel(s) and either reclear if you are ok with the existing base coat color, blend color (which I'm usually against), or base coat all panels and reclear.
Another option if the car is a solid color is to scuff/sand the panel(s) and use a high quality single stage paint. If you are very good about maintaining the paint (wax/polishing) and the car is covered from the sun when stored, you will save $ and any blemishes or orange peel in the paint work may be wet sanded out and compounded much easier; due to always having clear in the paint. Whereas with base/clear you can only wet sand as deep as you have clear.
However, if you have a very talented painter, you should not have much wet sanding, if any. All depends on what you are aiming for.

[diy83sc]

Thanks for these options to consider. Aside from the flaking, there are scratches, chips, and dings, so clear coat scuff and spray clear is not going to work for what I am trying to achieve. And that is for the car to have a fresh coat of paint, similar to the factory finish. While scuffing/sanding, I should somehow know how much I am taking off and be consistent panel to panel.

What is a good method to know how much color I am sanding off?

Would knowing answer to 1 help estimate how many base coats would be needed to get back to where I was?

How do I determine paint type that will be "compatible" with the original finish? It's an 80 Weissach SC, Black Metallic.

Most likely, there will be a talented painter doing the spraying - just want to learn as much as I can along the way.

Much appreciated.

Tony

[GotaT]

Being you have dings and chips you'll be applying some type of filler to those areas, either a high build filler primer, glazing putty, or "bondo" then sanded down smooth. When sanding the car for new paint preparation my personal experience has been, as long as the entire car is scuffed dull (I use red scotch pads or 400 wet sand paper) the new paint will adhere. You don't have to go to bare metal.
On chipped areas you'll need to feather out the area so that it is perfectly smooth. You'll often go to bare metal on these spots. If so, I use commercial primer, either high build which will also "fill" the low spots, or self etching for bare metal areas. both can be purchased at an auto parts store. I use Duplicolor brand.
Being a black metallic paint your painter should cover those areas that were primed first to ensure enough base coat color to cover the primer color.
At the end of the day of sanding the car should feel perfectly smooth and All edges should be dull. Any bit of shine left will potentially allow the new paint to lift off.
As a note, if you wet sand use warm water with a little liquid dish washing detergent and dont drop your sand paper as it may pick up debris causing more headache and work.

[Dpmulvan]

Don't use duplicolor paint on your car!! These paints have no catalyst or hardener and will not hold up. Use a two part epoxy primer for bare metal. Go talk to your basf jobber or talk to 962porsche he's the paint guru.

[962porsche]

not seeing your car it hard to tell just what is failing ? could be the clear or it could be the base color the has failed and is making the clear delaminate ?

my guess is it's just the clear coat .
you can strip off the top coats and leave most of the undercoats when stripping and doing so is often the best way to go . the OE undercoats are some of the best and if there is nothing wrong with them then it's a costly and waste of time to just remove them for no good reason .

the clear will or should strip off kind of easy with 80 grit on a DA sander . this will take off some of the base color and in places you will go down to bare metal .
after you 80 grit and strip off the failing finish you will want to go back over it with 180 by hand blocking or if your good with a DA sander you could use that but 180 every were you used 80 grit as you can not prime over the 80 grit sand scratch .

once your finished sanding you will want to blow off the panel/s then wipe them down with a pre cleaner . do your masking then mix up some epoxy primer . you want to spot in the areas with the epoxy primer over the bare metal spots only . there is no need to use the epoxy on areas were there is the OE finish still left on the panel/s .
you can with many epoxy primers go wet on wet . this is letting the epoxy primer flash off for 20 minutes or so then you can go over the entire panel/s with your filler or high build primers .
you will want 3 to 4 coats of a filler or high build primer you give you enough to block sand once it's dry .use a guide coat over your filler/high build primer to show you your high and low spots so you can sand them out .

never use a dish soap when wet sanding it's a BS myth and will do more harm then good in most cases .
most all hand soap has some kind of hand conditioner in it and will raze hell when you try and paint . if your using it so the paper doesn't clog up your not letting the product your trying to sand dry enough . people tend to use it for color sanding before buffing again another myth that it helps with any thing it doesn't . if you need to stop your paper from clogging then you need to wait till the paint has cured or your not changing your sand paper enough . trying to get to much use out of a sheet of paper .

bondo is not a product it one maker of a product that is called plastic body filler . I hope no one uses bondo brand filler it's cheap crap . for the same price you can buy a better quality body filler .
the myth that using body filler is a bad thing is just that a myth .
there is nothing wrong using body fillers if you use them the way they are designed to be used .

with all your products your using or looking to use try and use products that require a hardener .
you do not want to use products like spray cans and duplicolor they as far as I know do not have a hardener they are lacquer based or enamel with out hardeners . some spray can products have hardeners that you hit the bottom of the can and it punctures a chamber in the can and you can then shake the can to mix the two together .
I have not found one I think is worth the money to buy .

find a paint line you like and is easy for you to find and buy easily . personally I like and use BASF in my shop . I like basf as it's used on just about every high end car made by the manufacturer .

[diy83sc]

962 and others, thanks for sharing your experience. It's hard to see in some of the pictures what is happening. The roof picture shows dulling, white where I probably compounded through the clear coat. The other spots that are pasty white, those are areas where the clear coat failed. Also on the tail, you can see an area where it is peeling. Most of these are on the top side of the car... it wasn't garaged much. The front hood is chipped from the track. You don't want to see the bumper or the front valance, much worse.

On the hood, I did take an 80 grit to the paint by hand and it seems to come off easy. 962, you're saying stay away from media blast, chemicals and go at it slow with 80, 180, two part epoxy, etc. Makes sense to me. I have a shop that uses BASF RM line and proper two part epoxy primers. They gave me a decent quote to get the work done. Knowing what I learned from you all, I feel better prepared to discuss their approach and what I'd like to see done. One decision I haven't made is whether to do the door jambs. The rockers and the typical areas of rust above the jack point slots/re does not exist. The car is solid and want to consider leaving the jambs, hood/deck lid inners as is, preserving riveted paint code, decals, serial number and such. I'm not changing color. What's the thought there?

Tony

[rokemester]

hi this is a great thread, but appears to have run out of gas. any opinions on the re-spray? I'm on a similar path with silver metallic L980. My re-spray is a 10 footer, didn't invest in a windows out job, and the clear coat is coming away from the base coat. The re-spray color is close but not quite a match. It has a slight bluish cast which is nice but not stock and has been very difficult to match. Had to have a repair done to my passenger side mirror and it revealed the previous sins. Also curious about opinions on keeping the car original color.