Ok so this might sound like off topic but its relevant!

So on my dad's 300SD I've got some water leaks coming from the battery compartment area. Ive not looked into it but the water is clearly coming down from that area, going into the passenger cabin due to some poorly sealed welds on metal I installed..tricking down the frame horn thing and out a small hole.

I need to fix this and I was thinking. I'll take the battery out and use some brushable seam sealer. Then I was thinking hmm maybe I'll get some of that fiberglass repair stuff and just form it over the entire area..

Then I was thinking of that one thread about polyurethane filling motor mount to give them extra support and thought well why dont we just do that? Pour some kind of expanding liquid down there. Let it expand, seal up the holes and keep water from coming in/out?

Only problem is I don't know of such a thing. It would need to be flexible after expanded and water/weather proof!

Anyway, what do you guys think? Think its a decent idea? Bad? Does such a compound exist?

Seems like something I'd expect to see in the marine world...

Hm?
http://www.uscomposites.com/foam.html

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Cruise Control not working? Send me PM or email (jamesdean59@gmail.com). I might be able to help out.
Check here for compatibility, diagnostics, and availability!

(4/11/2020: Hi Everyone! I am still taking orders and replying to emails/PMs/etc, I appreciate your patience in these crazy times. Stay safe and healthy!)


82 300SD 145k
89 420SEL 210k
89 560SEL 118k
90 300SE 262k RIP 5/25/2010
90 560SEL 154k
91 300D 2.5 Turbo. 241k
93 190E 3.0 235k
93 300E 195k

DAP Dynaflex 230 ( in the caulking gun tube )

This is a household sealer that works well in the automotive environment even though they say not for auto use. It is a elastomer, a sort of rubbery seal when it drys. Tons better than silicone and you can paint over it.

It can be gotten in white, black , aluminum , bronze and clear ( clear goes on milky then drys clear. )

I have used 'truck bed liner' in a spray can for this type work. It is flexible, water proof, and easy to use. Just think of what a truck bed goes through and this stuff holds up very good in these conditions.

Paul

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84 500 SEL (307,xxx miles)

I have used foam almost same as the one in your link. But I used it for insulating cavities behind icebox in my boat. It is easy enough to use, but you do need to have an opening at top to pour mixed foam into. It expands a lot so you have to mix small portions and keep adding until it fills the cavity.

The problem I have, is how to rust treat the inside of my recently welded rocker panels. I can probably spray in rust treatment, but that will need to be re-done at intervals unless I can find cavity wax or similar. But then how to be sure all bare metal gets coated.

It did occur to me that the rocker panels could be filled with foam. But on the 300D, there are two drains which would indicate that some water drains into the rockers?

Problem with the foam could be when you again need to do weld repairs!

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Graham
85 300D,72 350SL, 98 E320, Outback 2.5

I've used building foam about the house - I'd never dream of using it on a car though! But right next to it on the shelf in the supermarket where I buy the stuff there's the anti-body; foam eater...

I guess it could be used.

Be careful with that expanding foam though - some of that stuff will push a very large window frame out of position as it expands. Here they sell two types; construction and non construction.

Alternative to foam that might look a little better - epoxy putty

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1992 W201 190E 1.8 171,000 km - Daily driver
1981 W123 300D ~ 100,000 miles / 160,000 km - project car stripped to the bone
1965 Land Rover Series 2a Station Wagon CIS recovery therapy!
1961 Volvo PV544 Bare metal rat rod-ish thing

I'm here to chat about cars and to help others - I'm not here "to always be right" like an internet warrior



Don't leave that there - I'll take it to bits!

I went with the DAP Dynaflex 230 and a fiberglass resin repair kit.

I found the source of my problem. The area under the battery, near the sway bar had some holes in it still that were not sealed up by metal nor were they sealed up by and of the coatings I used so I've cleaned off the area as best I can..the fiberglass stuff will do its best to seal up the hole, then i'll cover it with the 230 stuff. That should prevent the water from leaking down that body tube and into the cabin. I had another patch in the cabin that was just pop-riveted into place, water was coming from that due to the hole up stream.

That pop-riveted piece has been cleaned off, as best I can, and will be also covered with the 230 stuff soon as I can find my caulking gun. There was a tiny hole as a result of the water flow/rusting and my wirewheeling..that I used to apply a liberal spray of this internal frame coating I have. There is a small hole at the bottom of the body tube as I could see the excess coating drip out of it..

That hole is probably OK, in the event that water does get in the tube, it can just flow out that hole.

So hopefully I'll be able to squeeze another 3-5 years out of this poor car. The rear subframe, while still solid as ever has a nice amount of rust scale on it. What I'd love to do is drop it completely and give it the same treatment that I did the replacement control arm..but I just dont have time to do that.

Even if I did that I would still have to address the rocker rust. I wish I had a lift. I would just drop the subframe, yank the engine and go at the chassis for a month or two.

__________________
Cruise Control not working? Send me PM or email (jamesdean59@gmail.com). I might be able to help out.
Check here for compatibility, diagnostics, and availability!

(4/11/2020: Hi Everyone! I am still taking orders and replying to emails/PMs/etc, I appreciate your patience in these crazy times. Stay safe and healthy!)


82 300SD 145k
89 420SEL 210k
89 560SEL 118k
90 300SE 262k RIP 5/25/2010
90 560SEL 154k
91 300D 2.5 Turbo. 241k
93 190E 3.0 235k
93 300E 195k

I've successfully employed a method to seal holes of the sort in my Benz. Glued in Polly mesh material over the cavity. Used, as seen on tv, flexseal! Idk about floating an s10 pickup on water but the stuff is fairly usesfull. Other brands of spray flexible sealant in stores now.

Goes on easy and forms up hard. 8 months on and it's still holding. Almost hard to distinguish patch from the original undercoating material.

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Current fleet
2006 E320 CDI
1992 300D - 5speed manual swapped

former members
1984 300D "Blues Mobile"

1978 300CD "El Toro"

You will like the DAP 230. When using it if you get any on an unintended surface, wait until it half cures then just rub it off.