Expanding foam use

[p0689109]

I am busy working on the daughters Suzuki Jimny and one of the jobs is to repair a couple of rust patches on the body front lateral box section cross member. The rust is right next to the body to chassis mounting points . (these are unaffected structurally).(the Jimny has a detachable body) This cross member also suffers the rust around the headlamps and in the wheel arches on the same cross member. I have already repaired those areas a couple of years ago. These two new areas are in the engine compartment and access is impossible with the engine in. The clutch needed changing and so I decided to remove the engine to do that and then give myself the chance to repair the x member. The drivers side is behind the steering box so that had to be moved to be able to get at it. Now the reason this box section rots is that water is getting in to it as I found out when I cut the rot out. From where, I do not know, as it is supposed to be a fully welded structure but it does have a number of separate panels which are spot welded together and seam sealed so I should imagine through there.
To get to the point of the title of this thread I wondered if filling the cavity with expanding foam, after I have welded the repairs in, is doable as a sealing agent by filling the void and hence the water has no where to go. Has anybody used it in this sort of structure before? After welding I would drill a hole the size of the foams tube to insert it and then fit a grommet to seal it.

 

[BrokenBiker]

Depends what type you use...if you use open cell foam it will suck moisture in like a sponge and rot it quicker...I would plug any holes in the section then drill and tap a small hole, give a liberal dose of waxoyl then out a bolt in with a rubber washer to seal in up

 

[barracuda816]

I looked into this for increasing structural ridgidity and reducing NVH. There is some anicdotal evidence that expanding foam holds moisture. You cant use the single component stuff (builders foam) but the 2 pack stuff. It is used in boats and seems not to absorb water (if its closed cell) but if water gets in then it will not come out.

Edit: beaten to it.

You can also get varying hardness's. 2lb 6lb ect.

 

[Kayos]

A tin once exploded in the back of my van, it never rusted

 

[keithski122]

Vw used expanding foam in later beetle rear 1/4 panels.Guess what panels rusted on later beetles that didn't on early ones?..................yep rear 1/4s.I wouldn't use expanding foam.

 

[p0689109]

OK boys that that sorted. Who would have thought that it attracts moisture. In buildings too!

 

[barracuda816]

Im not sure it attracts moisture (atleast to any real degree) i think the main problem is it holds water (thinking condensation) I would like to do some real tests though because it has real potential as a NHV reduction aid.

 

[Spark plug]

I wouldn't fancy welding it in the future if it's filled with foam.

 

[Lufbramatt]

I think Ford used it on some of the later cortinas too, and they rusted for fun.

 

[Gareth0123]

On Halloween some teenagers sprayed the cheap builders expanding foam up the tail pipes of selected local motors.............. fortunately neither of our cars were done.

 

[pedrobedro]

Vw used expanding foam in later beetle rear 1/4 panels.Guess what panels rusted on later beetles that didn't on early ones?..................yep rear 1/4s.I wouldn't use expanding foam.

Alfa Romeo did this with some AlfaSud models and they had to be recalled to try to get as much out as possible by a local dealer. They melted it out through holes drilled in the box sections, really scientific. Open cell foam is the stuff you buy in blocks to make upholstery and filters isn't it ? The injected stuff is evil and if you confine it it can expand and warp whatever is containing it.

 

[500e]

Expanding foam dangerous stuff, as barra 816 said it will increase structural strength! BUT did it once on a Hillman Imp not a good idea, decided the car was flexing in the forests so fill the sills well there were a lot of holes on inner sill plates but not enough to stop the outer being removed from spot welds we watched as they went sort of pop bang & lower seam became detached & yes it was a pig to remove to re weld them

 

[bigegg]

Dont use expanding foam - it holds moisture, and degrades into??? (phosgene? hydrofluoric acid? - something nasty) under heat - like welding.
Lather it with bituminous paint/damp proofing paint

Ive also had success with pouring engine oil inside box section before sealing it.
The welding heat vaporises it so it coats the inside of the weld, rather than most other things which burn off the hot weld.

 

[wookie]

There was an episode of Car SOS where the owner had previously used expanding foam in the sills to stop water getting in, Fuzz wasn't impressed with it at all, suffice to say the sills were total rotten.

 

[keithski122]

Was the foam in there to stop water getting in or to "repair" the rust? I have seen that before.

 

[Member 66061]

Havent people used it to destroy speed cameras?

Its definitely not hair mousse....

 

[brightspark]

Havent people used it to destroy speed cameras?

Its definitely not hair mousse....

its good for putting up someone's exhaust using a long tube so it cant be noticed if they owe u money and don't pay or aggravate u for nothing

 

[Keith 66]

I am a boatbuilder & have seen foam used in boats for many years. Regardless of if its single or two pack it will absorb water sooner rather than later & will cause a hall of horrors if used anywhere damp. No way would i use any of it below the waterline.
I would not use it in any steel section as single pack is moisture curing anyway & condensation will cause rust.

 

[BrokenBiker]

A guy a few doors up used it on someone's car who had upset him. Filled the door seems with it and apparently the insurance wrote the car off as it would do too much damage to try and open the doors.

 

[Cobbler]

A guy a few doors up used it on someone's car who had upset him. Filled the door seems with it and apparently the insurance wrote the car off as it would do too much damage to try and open the doors.

Bit like the concrete lorry driver that spotted his wife's boyfriends car parked with the sunshine roof open some years ago ........... Several tons of concrete later ......