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'78 240D 4-speed greasel
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Discussion Starter #1
I'm trying to repair the rust on the floorboards of my '78 240D. There is some sort of pad made of some kind of tar material; it has hardened and cracked over the years and it is next to impossible to remove! I have just been using a chisel and hammer... :( Does anybody out there have any tips on how to more easily get this stuff off?!?! I want to take it all out so i can better assess and manage the rust.

I tried paint stripper to see if that would help but it didn't seem to...
 

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1981 W123 300D non turbo, 1992 190E 1.8 <=> 2.0
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The only thing that I've found that really works is a rigid paint scraping tool - a bit like a filling knife - and a blow torch.
 

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1981 W123 300D non turbo, 1992 190E 1.8 <=> 2.0
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Hot air? Hot air?

You need fire and lots of it!




(Seriously though it is pretty nasty stuff to remove. Not only will it probably stink out the car for a long time the fumes strike me as being especially unhealthy - I have noticed that on the rusty bits it comes off quite easily though!)
 

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'78 240D 4-speed greasel
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Discussion Starter #6 (Edited)
thanks for the tips guys!

I have a pretty good quality heat gun and it made a world of difference! My front and rear windshields are out so I just put a fan in the back blowing out so I had a good ventilation system; though it didn't seems to smoke much at all.
 

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1985 300D Gone 1985 230CE Perfect, 1984 300TD Driver, 1981 300TD Bad engine
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I'm trying to repair the rust on the floorboards of my '78 240D. There is some sort of pad made of some kind of tar material; it has hardened and cracked over the years and it is next to impossible to remove! I have just been using a chisel and hammer... :( Does anybody out there have any tips on how to more easily get this stuff off?!?! I want to take it all out so i can better assess and manage the rust.

I tried paint stripper to see if that would help but it didn't seem to...
What I found works best is to score the pad into several sections. Heat the floor from underneath to about 175 deg F with a propane torch. The pad sections will lift off nicely using a paint scraper. Mine were in good enough shape to reuse.
 

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'78 240D 4-speed greasel
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Discussion Starter #10 (Edited)
^^^^ Nice, what I scraped up so far had hardened like a rock and cracked so it couldn't be reused, but i might try to reuse the pads under the dash.

Does anybody have a link to a good DIY thread for repairing the rust?
I trying to determine whether to weld, fiberglass, or epoxy...
 

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Weld. ;) Everything else is a botch in my books...

The insulation under the dash is a huge piece - you wont get it out without removing virtually everything (heater, dash, center console etc. I removed only the parts that needed (with a hammer & sharp chissel) and glued it back in with seam sealer. :)
 

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Discussion Starter #12
The insulation under the dash is a huge piece - you wont get it out without removing virtually everything (heater, dash, center console etc. I removed only the parts that needed (with a hammer & sharp chissel) and glued it back in with seam sealer. :)

I'm already committed... :D I'm stripping the chassis so it can be media blasted in and out.

The body shop where I'm taking her (a very good respectable business) told me that epoxy will probably be stronger and outlast a metal patch...
 

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Discussion Starter #14
^^^ yeah. I was thinking of grinding the areas after media blasting, and then POR15-ing both sides and then fiber glassing the bottom and then epoxying the top. and then the body shop guy uses this spray-on product that is kinda like the original Mercedes padding - he'll guarantee it for 20 years...
 

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^^^ yeah. I was thinking of grinding the areas after media blasting, and then POR15-ing both sides and then fiber glassing the bottom and then epoxying the top. and then the body shop guy uses this spray-on product that is kinda like the original Mercedes padding - he'll guarantee it for 20 years...
If you do that then the bond strength is dependent on the strength of the paint not the epoxy. What are you thinking of using?

NuMetal?

What do the instructions on the packet tell you to do?

I see no benefit to adding fibre glass into the mix - that just another layer that can de-laminate and trap water that will then find its way to the remaining metal and promote more rust.


Good quality welding will without doubt produce the strongest joint - it is all about contact area - compare the performance of a decent weld joint with another bonded joint with the same contact area...

...sure you can make a stronger joint than a welded joint by making the point of contact larger. Brazed joints can be stronger than welded joints but they need a lot more contact area and more care and attention to the preparation of the surfaces. The same could probably be done with modern glue products but most of these are proffesionally applied to metal parts of automotive structures as an alternative to spot welding. In this situation you have the area - if you are expecting epoxy to perform well in a butt joint situation then I think you'll find that it falls out.
 

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Discussion Starter #16
If you do that then the bond strength is dependent on the strength of the paint not the epoxy. What are you thinking of using?

NuMetal?

What do the instructions on the packet tell you to do?

I see no benefit to adding fibre glass into the mix - that just another layer that can de-laminate and trap water that will then find its way to the remaining metal and promote more rust.


Good quality welding will without doubt produce the strongest joint - it is all about contact area - compare the performance of a decent weld joint with another bonded joint with the same contact area...

...sure you can make a stronger joint than a welded joint by making the point of contact larger. Brazed joints can be stronger than welded joints but they need a lot more contact area and more care and attention to the preparation of the surfaces. The same could probably be done with modern glue products but most of these are proffesionally applied to metal parts of automotive structures as an alternative to spot welding. In this situation you have the area - if you are expecting epoxy to perform well in a butt joint situation then I think you'll find that it falls out.
Very good info, Thanks!

The biggest hole is about 1-inch by 4-inches, and I will have that welded. The other holes are small (less than 1 squared inch) and there aren't very many of them. What I'm going to do is, after it's media blasted I'm going to POR-15 (Stop Rust Permanently with POR15 coatings-POR-15 Inc.) the entire cab/firewall. On the small holes I am going to use the POR-15 epoxy putty ( EPOXY PUTTY-POR-15 Inc. ) they say it's strong enough to drill and tap! I think that should be efficient and keep any rust from developing.
 

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Many people also rave about Islam - yet many other people see islam as deadly threat & evil. ;)

I'm with Army - I don't think much off chemicals as replacement(!) for metal.

Rust doesn't just 'grow' in the middle of a panel. In 90% of all cases it's creeping out of a joint or caused by a badly preserved screw hole (screws for brake line holder p.e.). The latter is easy to repair. The first can only be fought, if you grab the problem at the root - which is IN the joint, resp. overlap of the two panels. There's no way around separating the two panels, and either replace parts of it or take a chance and try some conservant.

The problem is to get chemicals - be it PO15 or anything else, deeply into the joint. That's also a problem after two new panels have been welded together with an overlap. That's very true and a lot of people don't admit it. BUT: and here's a big BUT: the chances of stopping rust are much higher if there's no initial rust anymore. You'r drawing on blank canvas, so to say. You have only to prevent future rust. And not fight existing rust AND prevent more rust under extremely disadvantageous situations.

The problem with rust is; it's no on the surface. It sits deep in the pores, between the crystaline structures of the metal. Like a zit. Or an iceberg. You see the tip - the majority is hidden. Expecting some chemical stuff to creep into any rust pore is - well - I don't know. A gamble? And the problem gets worse if you've used a wire brush and closed those rust-pores. They literaly get closed by this. Try it. Take a panel with some deeper rust, brush it with a wire wheel until it's shiney. And leave it exposed for some days. It'll turn orange again ;) Sure - you can encapsule & seal it - maybe for a very long time. But it's still there, waiting to come back.

Long story short: in my book the only EFFECTIVE and PROPER way of fighting rust is radical: amputation. And then new metal. Not by bonding, but by physically fusing it together, melt it into a big piece by strong electrical current.

A proper weld will not weaken the surrounding metal nor cause a big change in the material's properties.

Hope that all made at least some sense - english is not my mother's tonque :)
 

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...
Long story short: in my book the only EFFECTIVE and PROPER way of fighting rust is radical: amputation. ...
Indeed that's how medics deal with cancer too - cut it out!

Until we get some of those star trek whirring things that you just wave over stuff I think we're still stuck in the dark ages...
 

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These products seem way legit and many people rave about them. Here's a little more info:

POR-15 Rust Preventive Paint:
http://www.por15.com/Data%20Sheets/POR15ApplicationInfo.pdf

POR-15 Epoxy Putty:
http://www.por15.com/Data%20Sheets/regpu.pdf
I have nothing at all against POR15 products. I use them myself...

..well apart from the epoxy!


I think you need to look a little more closely at the information on the back of the tin (these are also on the web!)

Firstly you need to use their water based de-greaser

Then you need to use their (water based) zinc solution

Then the paint (that needs to be over coated if it is in contact with sunlight!)

If you want real paint over the top you then need their self etch primer...

then you can start painting...

It isn't the cheapest solution out there.


Many people say it is the best.


I've had mixed results. I now give it the three coats of the paint and then wait for six months to see if any more rust comes through...


...but then I live in a silly part of the world where it never ever stops sodding raining.




Take a look at the Eastwoods solutions too. People (in the American Mercedes world!) are sort of starting to look at these too. I have only had one failure with an Eastwoods product - when I tried undergone on W123 undercoating (wasn't really a fair test) - a part from that my experience so far has been that they do exactly what they say they do on the tin. But I haven't tried their rust stopper yet...
 
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