Painting Tips-Advice, masking and seals - PeachParts Mercedes-Benz Forum

87tdwagen · #1 11-24-2020, 10:59 AM

Hi All:
So I'm prepping the 300td for a respray, after 33 years, it's about time. I intend on using a third party to spray it for me, but will be prepping as much as possible. I have already shot the window, roof rack and trim in the correct charcoal and will be looking for the body shop to spray factory silver color on everything else that I dont remove beforehand.

One big open question for me is the door seals. Do you leave those on and just mask for paint, or are the seals normally removed prior?

I'd hate to introduce more work that necessary and this is not a full resto paint job, just a refresh. What have you had done or done yourselves with regards to painting the door frames, with or without seals?

TIA

Rogviler · #2 11-24-2020, 02:05 PM

Generally you remove seals and back-mask the openings from the inside. You'll find that masking tape often has trouble sticking to rubber seals if you leave them on. What I've always done is wipe the seals down with acrylic floor polish and that lets the tape stick really well. The best was Future but they don't make it anymore, so use the Pledge version, Weiman, or Quick Shine (or whatever you can find locally) if you want to go that route.

87tdwagen · #3 11-24-2020, 08:24 PM

Thanks Rogviler,
Great tips on the masking. If I leave them on, do you mask the lip of the seal that is flush with the body, or use the taping to roll the seal back onto itself and thus not be flush with the body with the doors closed so that the paint gets well into the gap?

I will be removing both door seals on the drivers side, but the right rear seal is in excellent shape and I'd hate to bugger it up on removal as replacement of this one nla seal is $400 for the rubber alone.

Rogviler · #4 11-25-2020, 12:57 AM

It depends on the shape of it, I suppose. I would usually mask at the edge that touches the paint though. As long as you prep well it won't be an issue, but if you have a little line of shiny paint that's also dirty running along the edge of your paint line then it will eventually start to chip away.

Diesel911 · #5 11-25-2020, 04:11 PM

If you leave the regular tan colored masking tap on over night or especially if it gets hot it is difficult to get all of it off.

That is why in the paint department they also have what used to blue tape but now comes in different colors. It does not stick as well and it costs more but it comes off when you want it to.

Junkman · #6 11-25-2020, 05:54 PM

An old painter told me that a trick to improve paint around windshield is to hold the seal up with a small dowel rod then tape the seal as normal to avoid over spray.

He said that this can result in almost as good as pulling the windshield.

I just had my SD painted. The guy who installed the rear windshield used to work in CA at a dealership when these cars were new. He cleaned the glass, attached the seal,installed the chrome, lubed the seal with WD40 (from a can,not spray) & wrapped the rope.

He taped the ends of the rope to the window then set the whole thing in place. Then he easily pulled the rope in stages working the window into place.
He slapped the window to help jiggle it into place.

I wish I'd taken a video. The process was beautiful with no muss, fuss or chance of breaking. Cost $60. I paid cash of course. He does work for bodyshops and car lots.

Rogviler · #7 11-25-2020, 09:45 PM

OMG for sure do not use house painting tape on your car, it's made for water-based paint. You will get a big mess. 3M green or yellow from the auto store only.

BirthdayBenz · #8 11-27-2020, 07:25 AM

3M makes a product specifically for masking behind trim. The tape has a stiff edge that goes behind the trim, then a sticky tape edge that you bend back around.

https://www.autobodytoolmart.com/product/3m-trim-masking-tapes

Junkman

Quote:

hold the seal up with a small dowel rod

I'll need to remember this one in the future. Junkman, thanks for sharing!

87tdwagen · #9 11-27-2020, 07:00 PM

Thanks for the great tips. Thanks BirthdayBenz for the info on the tape, I will see if I can use that on the passenger side doors where I dont want to mess with the seals and leave in place. The drivers side will be getting new seals anyhow, so I'll leave them off until after paint.

87tdwagen · #10 12-03-2020, 11:00 AM

Arrg, RUST on top rear door seal frame....

I removed nearly all of the rust via sanding and removing any weak sheet metal on the upper door frame which show up as notch outs in the pictures. But as you can see the channel is a bit buggered.

I had intended on encapsulating with POR15 but on such a smooth section like this with nearly no rust left, POR15 typically does not bond well.

The door is otherwise perfect, not even a ding on it, and while I can weld, my skills are not good enough to "patch-up" the current channel to perfection. I could weld on a new fold-down edge, but again, not sure how this would turn out without considerable work involved.

For now, I have zinc primered the frame as shown. My plan of attack is to JBWeld some of the top surface pitting so that it is nice and flat. Apply another zinc primer coat and top off with a 2K epoxy primer, later followed by a top coat.

As to the seal, I was thinking of applying 3M super weatherstrip adhesive in the top channel to help hold the seal and offset some of the grip loss due to the missing channel side walls, and hopefully bonding the area well enough to minimize moisture entry. I am also thinking of running a bead along the entire inner edge of the seal where it cups over the top of the door frame, again in hopes of minimizing water entry.

Any thoughts, cautions or advice is welcomed, either on the rust control or the seal installation method that I outlined above.

TIA