Rusty spot - how to fix... - PeachParts Mercedes-Benz Forum

MercFan · #1 07-05-2006, 10:57 AM

Sorry - I know this thread belongs in the Rust/Repair section, but I haven't had any replys to it there for a while now, so I'm trying my luck here -

Newbie rust repair question...

Any advice would be welcome. Does this look like it needs to be welded or can it be patched by some other means?

Thanks,
MF

barry123400 · #2 07-05-2006, 02:46 PM

That is a pretty bad small area. I would cut the simular area off a wreck and weld it in. That is called a patch panel. Make sure to rustproof the backside of the repair after completion. Also really check around as it is unusual just to have one spot but is possible.

d.delano · #3 07-05-2006, 03:36 PM

I know exactly where that rust is.
Get an angle grinder with a wire wheel, peel off that bubbling paint to the aft of the affected area, as in expose the extents of the cancer. Get all the loose scale off. Brush on a liberal amount of naval jelly. After that dries, coat the exterior with POR15. In the trunk well, if there is a hole, use some of that fibercloth then POR on top of that. If you wish, you could use the type of bondo that doesn't absorb water on the outside to fill, then order some paint to match from the Sherwin Williams auto paint place or someplace similiar. Just get a little bit, won't cost much. Get a friend with an airbrush to prime and paint. That's what I'd do anyway. Depending on how good you are that repair will last the rest of the life of the vehicle, will look presentable, and won't cost you too much time or money. Just be sure and POR the ***** out of the trunk well.
next step replace your rear window seal

MercFan · #4 07-05-2006, 03:45 PM

Quote:

Originally Posted by d.delano

Brush on a liberal amount of naval jelly.... use some of that fibercloth ...you could use the type of bondo that doesn't absorb water on the outside.. Next step replace your rear window seal

What's naval jelly and where do you get it along with Bondo and fibercloth - is that something from AutoZone or similar?!

You mean that rust is most likely a result of a bad rear-window seal?!

d.delano · #5 07-05-2006, 03:56 PM

It's phosphoric acid. It's called naval jelly because it has been used to kill the rust process on ships. It's also called rust converter or whatever the company marketing it wants to call it. Turns the rust into a grayish-black. You can buy it at Wally World or autozoo, etc. Not an exotic item.

The marine bondo is what you want, alternatively JB weld can be used as a fill if you have a small area to fill and allow it to cure properly, also really tough, sandable and paintable. Fibercloth is used as a base for the POR when it hardens. You put on a layer of POR around the hole, wait till it gets tacky to the touch, then apply your layer of fibercloth over the hole then POR over it all again. Hence you have covered your rust hole with something structural. Like installing a fiberglass patch panel if you will. Fill as needed, sand, paint. I read that you don't want an expensive proper fix, which of course would be a welded-in sheet steel patch panel with both sides of the weld treated. This would work well for your needs as I read them.
Save your paint chips that you peel off for the color-matchers.

bgkast · #6 07-05-2006, 10:16 PM

I am about to fix a similar area in my car. I am going to cut out all of the rust, then butt-weld in a patch panel. I plan to do a pictorial on the repair and post it here. There are other ways to fix it, but I believe that this is the most permanent repair.

MercFan · #7 07-05-2006, 11:41 PM

Quote:

Originally Posted by bgkast

I am about to fix a similar area in my car. I am going to cut out all of the rust, then butt-weld in a patch panel...

Yes, I'd like to see the 'how-to' on this type of fix... Where are you going to source the sheetmetal for the patch panel?! Using MIG welder to do the job?! My dad is a welder -he lives in Michigan though and I don't currently have a welder maching... hmmm - maybe a shopping trip is in order... hehe

bgkast · #8 07-06-2006, 02:03 AM

I found a member of this forum with a car headed to the crusher who was nice enough to cut it out for me. I will be using a funny little 115 volt wire feed welder that I got at harbor freight for $120. Not the best piece of equipment, but it should do.

MercFan · #9 07-06-2006, 10:40 AM

Quote:

Originally Posted by bgkast

I found a member of this forum with a car headed to the crusher who was nice enough to cut it out for me...

Anybody know of a donor vehicle in the Denver area and surrounds that would have a solid right patch panel available?! If so, let me know... If no luck finding one, I'll probably go with fiberglass/bondo combo... hehe

whunter · #10 07-06-2006, 11:19 AM

Quote:

Originally Posted by MercFan

Sorry - I know this thread belongs in the Rust/Repair section, but I haven't had any replies to it there for a while now, so I'm trying my luck here -

Newbie rust repair question...

Any advice would be welcome. Does this look like it needs to be welded or can it be patched by some other means?

Thanks,
MF

This is an impact structural area, it needs to be cut out and new metal welded in.

Note:
This thread can be merged with your other thread, at a later time.

Have a great day.