Has anyone used expandable foam insulation in an inaccessible area such as a body to frame mount to stop rust from the inside out. Theory being if the pocket is filled with closed cell polyurethane foam, nothing such as mud can get in to rust it or any rust that was already inside couldn't rust any further due to no oxygen getting to it anymore. Any thoughts? Thanks, Lenny
Sounds like a horrible idea. Foam by definition has small holes. I would spray in something like POR15 to prevent rust
Bad bad bad bad bad idea... That stuff breaks down after a few months and it holds water like a sponge! It causes rust problems more than anything
Worst idea ever! I have seen so many DIY "repairs" done this way only to rust out later on a larger scale. Why not try stuffing the cavities with wet sponges and get it over with fast?
Bad idea. The foam retains moisture and makes rust worse. I know that Ford tried it on a 1990 F150 Supercab pickup that I bought new. The area with the factory applied foam was first to rust out.
!!! DO NOT DO !!!! They used on campers at one time , and they all rusted out. sounds good but does not work. (i am talking about the stuff u buy at the home improvement stores, like the rite stuff.) do your research!
Been there and done that, don’t do it unless it is something that you just don’t give a shit about .
I've worked on cheap RVs with this crap jammed in every space and void. Where it was touching any metal or even fiberglass panels the was rot and it was moldy and stunk.
ditto no to spray in foam , friend got a 69 mustang that had the frame unibody frame rails filled with it , collected moisture an rotted the rails , could nt cut em out because the torch or disc grinder caught it on fire and made noxious fumes , so he parted the car out and scrapped the body shell
MANY cars from the last 10-12 years used foam to seal voids from dust and road noise. I'm a collision tech and I get to see some of those areas as cars get cut apart for new panels etc. It causes rust...even with the high tech internal coatings and epoxy primers etc all manufacturers use in modern cars. I have a 2002 Dodge Caravan that hasn't seen winter use in as long as I've owned it...5 winters total. It's in excellent condition...except at the rocker panels EXACTLY where the foam filling was done. Those sections of rocker panel are rusted out and I'll have to replace them this summer! I'll take some pics this summer and post them to show the damage foam can cause. It would destroy an older car with bare steel inner panels in no time flat. Don't even consider doing it.
I echo the comments made, and being in MN, you'll quickly find out road-salt eats the stuff away in no time.
I have never put any expandable foam in. But I have taken plenty out, on cars I had to do rust repairs on...
With all the replies that say it causes rust (which it most certainly does) I can't believe that anyone would even believe it could work to begin with. There is no such thing as closed cell foam. Even if they call it that, it will eventually soak up water like a sponge. Closed cells my ass An example that what seems like a good idea is often something else.
anybody see the SEPT. 2010 streetrodder article "roof inserts for sedans" . they put spray foam between the new roof skin and the support bows after it was all welded in, what do ya'll think about that??
the term "ghosting" comes to mind. Think of a 90 degree day and a storm cloud coming over.......................................................
what if you put a strip of dyna-mat or similar between roof bow support and the new roof skin instead of the spray foam ?
Take a look at a full size van. They use a spongey foam on the roof bows against the skin to stop the roof sounding like a bass drum. Here's the thing, it's on the INSIDE of the van not in the fender or the rocker getting blasted in salt spray and covered in fenderbergs...
Wow dude a little on edge today? The guys was just adding to the original question about expandable foams. Maybe he has a application he thought he could use it for and thought that while people were talking about foams in this post he might get some info.
The company I work for has both "open" cell & "closed" cell spray-on foams and the only place that I would use either would be in a closed area as a sound deader and would not be in an area that moisture could get in. If is stuff gets wet - beware of rust - oh sure you are thinking of all those cool foam water toys that kids play with in the swimming pools - well they aren't attach to steel are they!
I used it to rebuild some rocker panels on a '95 Taurus. Worked great. Sprayed into what was left of the original rockers, let it expand/dry overnight then carved myself some new rocker panels. Finished them off with a wonderful application of spray can undercoating and PRESTO brand new (appearing) rocker panels. I guess I should add, this was just an attempt to make it look more presentable and the car will be "put out of its misery" at some point this year .
In the areas where I can't get bare steel coated, I use transtar's ambercoat. Used it on the inside of my frame. You can get it with an extension wand(30" or 36", can't remember) with a 360 degree tip with it. Best thing to do is to mock up the area needing coating by making a cardboard template and practice spraying until you get the coverage you're looking for. It's available at oreilly's too. Just tossin' it out there. JM$.02
I've seen some REAL horror stories with this stuff. A guy tried to fix a warped fiberglass hood by injecting it between the inner, and out layers to make it more rigid. It expanded and REALLY warped the crap out of the thing. He threw it away. I've heard of bodymen losing a socket down a tight spot where they couldn't get it out, so they shot some of this stuff down there to stop it from rattling around...
There are two types of expandable automotive foam flexible and rigid. The flexible is designed to flow around solid objects so that it doesn't push things out. It is used in doors of modern cars for sound deadening and it flows out so that when it gets between the intrusion bars and the door skins it doesn't push the door skins out. The other type is Rigid which is designed for pillars etc and it is not designed to give and flow around things it is more for adding rigidity to hollow structures like a pillars in new cars. Neither are designed to be exposed to the elements.
Ive never done it but how bout pouring some oil in the frame? might not be the greenest thing to do but might help stop rust
i once looked a 67 gtx the guy had for sale cheap built 440 /trans .....opened the trunklid and the doors and all the holes the body had in it were full of expandable foam shut the car up and walked away ..... when i bought my 69 mustang i thought one of the 1/4's behind the rear wheel looked kinda odd the whole corner had rusted out/off and the po filled it with foam and then primered the out side of it needless to say i put my foot inside the trunk and gave a nice big firm kick and it fell out on the ground i kept the glob around for awhile to show people some people should not be allowed to do .......bodywork as far as dyna mat or simular between the roof and supports i think it would work pretty good
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