Update with scary picture - W204 2008 rear subframe failure

[Wighty]

Many subframes have vent holes, and it makes more sense to spray Waxoyl into these - watching to see when the mist comes out of the opposite holes - than to treat just the external bits you can see.

There is a flexible wand, about a metre long, that can be fitted onto the normal Waxoyl gun that will slide into a subframe or sill through any small hole, and can be drawn through while under pressure, so that every internal surface gets treated.

Dinitrol do a similar wand that I bourght that gets into the holes . It was a very Waxoyl like stuff (Dinitrol)

 

[Jim2]

Many subframes have vent holes, and it makes more sense to spray Waxoyl into these - watching to see when the mist comes out of the opposite holes - than to treat just the external bits you can see.

There is a flexible wand, about a metre long, that can be fitted onto the normal Waxoyl gun that will slide into a subframe or sill through any small hole, and can be drawn through while under pressure, so that every internal surface gets treated.

Yes, Umblecumbuz, you are right. These "Vent" holes are actually assembly guide holes. There are corresponding pins on the assembly jigs, and the box section's, plates etc are dropped on to them so that they are pre-positioned for welding etc. For the welding, metal is liquidized and drawn together from both piece's to be joined. So while the actual weld itself is very strong, both the panels will be weakened on either side of the weld due to this loss of metal for the weld. And that's why they tend to rust and break along the line of the weld. The metal is actually thinner on either side of the weld.
For rust protection ( especially in box section's ) we used a flexi pipe with what resembles a plumbing jetter head ( This is a head with a powerfull jet of water forced out to the front, and several other rear facing jets, which propel it along the blocked pipe, and clearing the blockage ) The spray head we used was shaped a bit different, and sprayed out in every direction, so all the metal in the box section would be covered.

 

[Jim2]

I'm surprised there hasn't been much noise in the press about this. It's a major safety issue - can you imagine an arm coming loose at motorway speeds?

I can't understand how the one in the pic did not come apart.......only a matter of time though.. it's like an accident on it's was to happen.......

 

[00slk]

Many subframes have vent holes, and it makes more sense to spray Waxoyl into these - watching to see when the mist comes out of the opposite holes - than to treat just the external bits you can see.

There is a flexible wand, about a metre long, that can be fitted onto the normal Waxoyl gun that will slide into a subframe or sill through any small hole, and can be drawn through while under pressure, so that every internal surface gets treated.

Best result there is is to rust protect before the rust starts, no good waxoiling a rusty part, it'll carry on rusting underneath the preventative.
This car was waxoiled while the new parts were fitted and the waxoil carried on over the rusty parts too, look at it now after 20 years. It probably started rusting soon after it was waxoiled




Maybe rust treatment has improved over the years, but there is no substitute than new steel.

 

[Jim2]

Best result there is is to rust protect before the rust starts, no good waxoiling a rusty part, it'll carry on rusting underneath the preventative.
This car was waxoiled while the new parts were fitted and the waxoil carried on over the rusty parts too, look at it now after 20 years. It probably started rusting soon after it was waxoiled

View attachment 47506
View attachment 47507
View attachment 47506
Maybe rust treatment has improved over the years, but there is no substitute than new steel.

Yes 00slk, agreed 100%..you can slow down the "progress" of rust, but once it gains a foothold, that is that. Personally, I thought that the rust problem ( especially in higher value cars ) had been solved....seemingly not though. Another cause of rust ( sealed or not panels) is the actual composition of the metals used....it is not unknown for some metals to start rusting from inside out, literally due to impurities in the metal itself. The other possibility is that rust is all part of the grand plan....so your car has a "LIFE" ( but limited.... ) and you will have to change it..and of course spend money !!!

 

[star]

I use Acf 50, did a test on a piece of unprotected sheet steel, coated one half and left it outside for a month, half corroded, the other as new. We then coated the rusty half and left it outside for another month. No more rust appeared.

 

[00slk]

Sounding like rust preventatives are progressing nicely then. I've taken note of that product

 

[Jim2]

I use Acf 50, did a test on a piece of unprotected sheet steel, coated one half and left it outside for a month, half corroded, the other as new. We then coated the rusty half and left it outside for another month. No more rust appeared.

The more you can put between metal and air, the better. Rust is an oxide caused by oxygen in the air, coming into contact with bare metal....so even if you have rust in a panel, once it is coated to prevent contact with the air, it will definitely be better than neglecting it.

 

[LostKiwi]

The more you can put between metal and air, the better. Rust is an oxide caused by oxygen in the air, coming into contact with bare metal....so even if you have rust in a panel, once it is coated to prevent contact with the air, it will definitely be better than neglecting it.

Not just oxygen in air but also in water. That's why steel rusts underwater too.

 

[Jim2]

Not just oxygen in air but also in water. That's why steel rusts underwater too.

yes that's true, Oxygen is the big enemy of metal, even under water, or any where else either. I would imagine that even in the International Space Station, the metals used have to be rust resistant. Some kind of alloy, I would guess.

 

[LostKiwi]

I think external surfaces there would be fine in terms of rust, it's more abrasion from space dust out there.

 

[Blobcat]

Put mine up on ramps today and it looks fine from what I can see. I had a feel around as much as I could and no crusty or flakey bits.

It’s a bit difficult to photograph but below is what I have. Any feedback appreciated.

 

[ajlsl600]

think its just a sad fact, benz and others living on past reputations and now going to the lowest bidder for everything.incl material supply. in reality a ford kuga is probrably as well protected underside as a 70k benz, and will last as long . i pressure wash all my motors underside each yr with all covers off, then i plaster everything with wd40 or af50 and put the covers back , i have surface rust but as far as i know ,nothing terminal on any of my cars, closer inspection this comming summer, i always wash on hotest days possible to prevent lingering water wherever possible. would say as far as most car makers are concerned design life done at 10 yr. unless annual preventative is done. another make us into perpetual consummers scheme i would say.

 

[LostKiwi]

Looking at those pictures in the top 3 there appears to be a drain hole (very wet in the 3rd pic) which looks to have a design flaw. Hard to be sure but the way the hole is made appears to create a lip around the lowest area meaning the water can't drain away?

 

[Blobcat]

Looking at those pictures in the top 3 there appears to be a drain hole (very wet in the 3rd pic) which looks to have a design flaw. Hard to be sure but the way the hole is made appears to create a lip around the lowest area meaning the water can't drain away?

That’s drivers side rear towards the front of the car. It does look a bit like that, I’ve dried it off and sprayed it with grease for the time being. I’ll get some waxoil or similar in there later.

 

[A.J.]

View attachment 47498 View attachment 47497 It seems to be getting worse, we have two c classes in and a 171 SLK all needing new rear frames!!!

This is the one out the SLK, belongs to a old forum member......

Why wasn't this picked up by the MOT testing station long before it ended up like this. Could it be a case of ignoring advisories although that is way past an advisory stage

 

[ajlsl600]

Looking at those pictures in the top 3 there appears to be a drain hole (very wet in the 3rd pic) which looks to have a design flaw. Hard to be sure but the way the hole is made appears to create a lip around the lowest area meaning the water can't drain away?

design flaw, or homage to the idea without really commiting to the prevention of the same ? manufacturers aint daft!!!

 

[alexanderfoti]

I use Acf 50, did a test on a piece of unprotected sheet steel, coated one half and left it outside for a month, half corroded, the other as new. We then coated the rusty half and left it outside for another month. No more rust appeared.

I use the same, on cars that come in and have a big of surface rust here or there, it gets sprayed under to keep it at bay.

 

[Josonic]

Thanks everyone. My 2008 C-class W204 rear subframe was found to be rotted out this week. Phoned local Poole Mercedes dealership and asked for the after sales manager in regard to this ‘serious safety issue’. He claimed to have never seen/heard of this issue, said that as it was over 8 years old, he could not see that Mercedes would be interested, but that if I got car to them he would inspect it. I called my breakdown provider (auto-aid) and they transported it for me (free). They inspected it, said it was unsafe to drive and that they would contact Mercedes corporate. A few hours later, I got a call to say that Mercedes had agree to pay for subframe, including labour. Manager pointed out that I also had an issue with ‘break fluid lines’ and that they need to be replaced as it’s usually very expensive as it requires the subframe to be removed. I am obviously very happy with the outcome, and hope that if you have the same issue, have the same response.

 

[mercmancdi]

The Mercedes I usually drive can be from 5-15 yrs old , every time there are getting brakes etc done I do all round subframes and any metal brackets with a liquid called krust then once it had worked I use a spray of dremtol rust protection.
Seems to work very well.