W124 Driver's Rear Wheel Well Rust Cause?
 

Hey everyone,

I was poking around my 300D a few week ago and found a grommet that crunched when I poked around it. It looked innocent enough. Nothing screamed HEY IM RUSTED!

I took out the angle grinder and attacked it for a little bit today and found that it was all rusted. It was isolated to the area around the grommet. The grommet above was kind of like that as well.

Is there some kind of drain or something that would leak into here?

I'm going to patch over the two grommets either by welding or riveting, not sure yet exactly.

Then I'll put on some treatment to prevent rust. Lather on some seam sealer and paint it.

Pics:

W124 300D Rust Repair 7-20-13 - Imgur

The 124/201 were the first model to feature galvanized steel.

The technology for continuously dipping the steel, after rolling it, in hot zinc, had just been perfected in Germany in the early 80s. It would take a while (late 80s - early 90s) for it to come to America.

(In a former life I had a part in the control systems for the first 80" wide galvanizing line in North America back in the mid 90s. The output of this plant fed one of the major auto manufacturers. 80" wide was huge for them, it allowed them to make large SUV-sized stampings in one piece.)

Be thankful it wasn't a 123, that would have been much worse. They relied on asphalt and paint to protect the steel, any breaches of the asphalt coating invited water in and it festered unseen until you were left with an asphalt and iron oxide sandwich.

However galvanized steel is not impervious to rust. If the galvanized coating is broken, the steel will still rust. Vigiliance is still a must especially in the northern states with salted roads or coastal areas.

This is exactly the corrosion I just posted about a short while ago here:

http://www.peachparts.com/shopforum/diesel-discussion/340688-124-corrosion-issue.html

You are a better man than I for welding a patch. I did a "cold patch" using a panel and silicone seal and undercoating.

Rgds,
Chris W.
'95 E300D, 398K

Chris,

Did you ever find the cause of the rusting?

Think it was something from behind the grommets or just stuff on the front side?

Seems like a common rust point. The passenger side is in good shape.

It's usually from driving on salted roads. You wouldn't find that on most southern/western cars... good thing you caught it early.

:boat:

Rust is clearly coming from the back (in)side, not the front side exposed to the outside. The undercoating appeared intact on the visible side, but you could clearly see the bubbling rust was in turn bubbling up the undercoating from the back side.

I didn't bother to ponder how the moisture must have gotten that cavity area, but interestingly you could see undercoating wax on some of the surfaces inside there. Clearly they didn't undercoat the side which had the hole and plug, however!

Rgds,
Chris W.
'95 E300D, 398K

Finished up the repair tonight. Looks pretty good if you ask me! After the welding was complete I drilled a hole in the top patch and liberally sprayed some internal frame coating. It came with this nifty spray hose. I made sure to snake the hose in both direction so that I got the upper wheel well cavity as well..just in case. I also sprayed the rocker panel area too. Wish I could have taken pictures before and after. It did an awesome job of coating the entire area.

This stuff:
Internal Frame Coating w/Spray Nozzle | Eastwood


After the internals were coated, I painted the outside with two coats of the rust encapsulator stuff and then generously applied seam sealer all over the area...let that sit over night..then painted it with chassis paint.


Updated the album:
http://imgur.com/a/lyGXY

Tell me whatcha think?

Ditto.

I had a mysterious water leak in my 92 w124 on passenger side. Front and rear carpets wet. First checked all drains in front, sunroof, back. Removed seats and pulled back carpet dried it 100%. Ran the hose over entire outside places where the drains are. No water. Put it all back together. Put car back outside in the rain. No water. As soon as I drove it through a few puddles then I heard water sloshing from the back floor to front passenger side floor area again. Took it all apart again dried it etc. It turned out it was cracked rubber grommets in the outside back wheel area where MB presumably sprays water proofing I guess when they build the car. The rubber hardens then cracks and leaks. Splashing through a puddle had water enter there and it went into rear floor area first and then to the front when you applied the brakes. Check the rubber grommets in your wheel bay. Seal them and that problem wont happen!

Took quite a bit of time to dry out all the channels etc along the rockers inside.

I cleaned the wheel area and made a nice patch out of roofing cement and 1/8"thick rubber. problem gone.

i know this is old, but no need to start a new thread. I have water on the drivers side floor front and rear. i ran hose over the entire car and coul dget nothing but i did find that there are two opens holes in the rear wheel wells with no plug. sprayed some water there and it did go in, but it looked like it had never been wet there before. I have the carpet and rear seat ushion out

James .You will find it the damp that holds at the rear of the rubber bung or grommet as the under seal is broken ,and water gets at the back of it and it never dryes out. .I had one just the same, only it was in the boot floor .I would check that also .Clean it up and give the bung a nice dolup of rust inhibitor ..

Also check the foam drain tubes at the bottom of the heater box. These disintegrate, and then the water travels under the carpet from front to rear. Pull the vertical carpet panels along the transmission tunnel to check the tubes. For the hose test, run water around the base of the windshield wiper, it drains into the heater box and out through the foam tubes (should normally drain out under the car, on top of the transmission). Water leaks can be a PITA to track down...

http://www.w124performance.com/image...rain_tube4.jpg

:boat:

This is a good thread so I’m bringing it back even if the old original posters are not on it anymore. I noticed the same thing in my 91 300D. Crunchy, dry grommets that have rust forming around them. I have not encountered any moisture there, but there are signs of past history with water in the area where the vacuum pump lives under the back seat. I think this is the cause of water there, and would explain why even when my car sits in torrential downpours, I don’t see signs of water, yet obviously there was moisture at some point.

Question now is how to beat close up the grommets.

I don’t have the capability to weld in metal, but I can use structural epoxy and that would probably be a fine repair. Not sure if I want to cut little patches of good grommets and affix them to bright metal where the old ones were, or just cover the holes smooth.

Thoughts?