MB Paint is tough stuff - PeachParts Mercedes-Benz Forum

martureo · #1 12-02-2011, 11:42 PM

I've read a few times where people have remarked that the original paint/primer on their w123s were pretty tough but I hadn't experienced it until today.

I pulled the subframe from my wife's "new" wagon to replace the bushings, springs, half shaft boots. I used the method shown on here awhile back of unbolting the subframe bolts and the differential mount to "roll" everything out. After I removed all the bushings and rubber bits I went a little crazy and wire brushed the entire subframe and the trailing arms down to the metal.

I just have to say DANG that stuff would not come off! I have only a little history of the car and I know from a previous set of service records and a purchase receipt that it's lived in Southern Virginia several times. So I was surprised that I only found a few quarter size spots of surface rust on the subframe and trailing arms.

Whatever MB put on subframe parts back in the day really works!

t walgamuth · #2 12-03-2011, 07:04 AM

I am kindof lazy. I would never have removed any paint. I would have brushed the rusty areas, rust bindered them and touched them up..

We are very unlikely to meet the quality of the factory paint in our driveway or garage.

Just my opinion of course.

KAdams4458 · #3 12-03-2011, 09:36 AM

I have to agree that as long as most of the finish is intact on driveline and suspension parts, I will do no more than remove the rust and touch it up.

Speaking of tough primer, my body shop friend came over last night and helped me clear away more rust on my '77 300D in order to prepare it for exposure to the elements. The deck lid seems to be an MB replacement part bearing black e-coat with only one coat of paint, and the star revealed a 126 prefixed part number instead of the expected 123 variety one would expect to see on a '77. The non-original primer and paint were lifting badly, so he took all of it off with 80 grit on a DA sander, but the e-coat was apparently tougher than anything he has seen on modern cars. Luckily, at least half of it was intact and got to stay.

While he was doing the deck lid, I was at the front of the car digging urethane, three coats of paint, and rust out of the windshield pinch weld with a heavy wire wheel. Rust? No problem. The top two coats of repaint? No problem. The base and clear from the factory is kind of tough, but the beige looking primer that the factory applied to the bare steel is seriously tough stuff! I don't know what that stuff is, but so long as rust isn't a problem, I see no reason to sand through it on the rest of the car.

This is slightly off topic, but speaking of rear subframes, I would like to swap the differential in my '77 out for the rear from the '83 turbo car, since I am already swapping the motor and tranny. Would it be easier to just drop the entire sub frames and trade them between cars? it seems to be all the rage these days. I obviously still need to do shocks and replace the differential fluid, but since the subframe rubber mounts in the '77 look a little dry and cracked, the idea of dropping the entire subframe for a swap is sort of appealing.

panZZer · #4 12-03-2011, 02:56 PM

I remember reading MB didn't start the serious Rust prevention regiment on the assembly line coatings until 1981

vstech · #5 12-03-2011, 08:34 PM

if you are talking about front subframe, it's not removable, the rear is, but you have to disconnect practically everything to get them out, so it's not easier... if your 77 subframe is intact, leave it, and just swap the mounts. beware, the subframe mount on your 77 is likely COMPLETELY destroyed, extremely difficult to remove the center bolt! use of a 6' cheater on the 24" breaker bar and I still could not undo the bolts, I had to get my 6'8" TALL BROTHER to turn that pair of bolts!

martureo · #6 12-03-2011, 09:12 PM

Quote:

Originally Posted by panZZer

I remember reading MB didn't start the serious Rust prevention regiment on the assembly line coatings until 1981

Good to know. The subframe I was working on was from an 83.

KAdams4458 · #7 12-03-2011, 11:36 PM

Quote:

Originally Posted by vstech

if you are talking about front subframe, it's not removable, the rear is, but you have to disconnect practically everything to get them out, so it's not easier... if your 77 subframe is intact, leave it, and just swap the mounts. beware, the subframe mount on your 77 is likely COMPLETELY destroyed, extremely difficult to remove the center bolt! use of a 6' cheater on the 24" breaker bar and I still could not undo the bolts, I had to get my 6'8" TALL BROTHER to turn that pair of bolts!

Yep, I meant the rear subframe. I did mention rear differentials, after all. I feel bad being off topic, but doesn't the sub frame need to come off anyway to replace the mounts that, as you have already mentioned, are likely completely destroyed? (Actually, they are not too ugly, but it is time to replace them.)

Also, I have no problems with stuck bolts. Air tools are great, and my '77 just isn't very rusty. Don't hate me or anything.

KAdams4458 · #8 12-03-2011, 11:41 PM

Quote:

Originally Posted by martureo

Good to know. The subframe I was working on was from an 83.

I think that the corrosion preventative measures were applied only to the body, and not in any way to the subframe or suspension components, but I could be wrong.