Foam filling sills?

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fredp

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Throwing this idea in for general discussion and comment.

I was talking with a mechanic who does a lot work setting up Skyline GTRs for show and go and one of the things he talked about was filling the sills with expanding foam, after rustproofing, to increase rigidity and stop future water penetration. He also mentioned that some new cars coming out of Japan have this done in the sills and A pillars as part of the rustproofing and to help provide strength.

Could this be a possible option for the E9? I know this is not for the purists but for those of us just wanting to protect our rides, what do you think?
 
might work

but then again it might not.

My rationale is that it's probably useful to do this to a new car without prior rusting in the sills, but to do it on an older car which probably has pre-existing rust may not be appropriate.

But are we to assume that when body corrosion is largely a forgotten event because automakers are doing a better job at the design station, using better steels, paints and production methods, that new GTRs are still prone to rusting sills? I wonder if someone is not making a quick buck here. It wouldn't be the first time.
 
I believe this is a bad idea for the following reason: Since the inside face of the sills probably have some surface rust and are dirty, the foam will not adhere well to it. Then, if water does get inside it would leave a place for moisture to wick (and remain) between the panel and the foam. Perhaps on a new clean car this method would be ok.

You would be better off using a spray-in cavity wax that penetrates the seams, since these are usually the areas that rust (pinch weld, fender overlap at rocker, etc.).
 
Just FYI...
A friend of mine did this to a 2002 and the difference in the body and chassis stiffness is astounding.......
He did the sills, the A pillars, the B pillars, and the front frame extensions.
I was VERY skeptical.... But it REALLY made a VERY noticeable difference in an old creaky car....... It feels like a modern car now... Very tight and stiff.
Dave Ganzer
 
foaming

This is in my opinion a very bad idea: moisture will always find its way between the panels and stay there untill it rusts through. You will be confronted with an enornous amount of work trying to get the foam out to do the repairs because you can´t weld with foam around. Foaming was tried in the 70´s and 80s and never gave positive results. Now, if your friend´s car is so much stiffer do to the foam, then it may be time for him to get new rocker panels.
 
Gerrit said:
This is in my opinion a very bad idea: moisture will always find its way between the panels and stay there untill it rusts through. You will be confronted with an enornous amount of work trying to get the foam out to do the repairs because you can´t weld with foam around. Foaming was tried in the 70´s and 80s and never gave positive results. Now, if your friend´s car is so much stiffer do to the foam, then it may be time for him to get new rocker panels.
Click to expand...

+1
 
Having done significant body cavity waxoiling, most cavities have drainage holes so I can't imagine filling them with foam and having moisture come in from the top or elsewhere and pooling somewhere. I'm for waxoiling out the wazoo every couple years or so and keeping the drains clear - allowing for ventilation/drying/condensation prevention and going from there - keeping the car as dry as possible as a general rule.
 
What really works--

I'm +1 with Steve--keep them as dry as possible--one rule--NEVER A HOSE SPRAYING OVER THE TOP!! It will find its way into doors, quarter panels and behind and under trim--none are beneficial to a Coupes longevity.
 
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