To fill or not to fill?

[Robertsocal]

Hello all,
I was putting the finishing touches on befoer going to get my paint work done, and while looking over (under/inside) the front fenders which i had previously cleaned up the entire inside wheel wells and fenders (sand blast/air needle etc.. followed by 2 sage rust converter and preventive coating, supposedly permanent, then primered, painted and undercoated best i could do without removing fenders).
and was looking at some of the areas water could sit like where fenders and linings come together, in the upper box area etc..

My question is has anyone decided to use a good expansion filler in there to keep everything out of the gaps?
Granted would make removing the fender less than fun, but then maybe it would not ever have to come off!
Suffice it to say some of those areas were less than easy to get to and clean up, and I have no desire to do it again in the next 15 years, nor if I sell her do I want anyone else to ever have too!

Thoughts?

 

[Stevehose]

I've wondered the same and the experts say it's best to not fill them, you'll never displace all the air and moisture/condensation will be trapped. Better to let them be able to dry out and not to put the car away until they are.

However for long road trips I have sliced closed cell pipe insulation into strips and crammed them up into the fender seams as well as taped off the box openings to keep any water out during the trip. Once back to dry land or clear weather I remove the pieces and keep air moving and facilitate drying.

I also remove the two small rubber seals at the back of the tops of the fenders in the engine compartment in order to allow air down there too. I only install those for road trips also.

I have also blasted cavity wax into any and all orfices I could find.

 

[Robertsocal]

So fill the cavities but not the boxes?

 

[Stevehose]

No the cavity wax just coats the metal and gets into crevices, it doesn't seal anything off. All other sealing is temporary for possible inclement weather.

 

[John Buchtenkirch]

I made thin (.024) stainless channels to seal off the gap between the fender top and the skirt to keep water & road dirt out. I glued the stainless pieces in with 3M fast & firm caulking and then undercoated it after the caulking set up. I don’t see why about a 1” diameter plastic hose filled with expanding foam wouldn’t work nearly as good as the stainless pieces I made up. One of the drain holes behind the radiator support was clogged & opened up by me. I’m not a fan of the “air it out idea” at all, 40 plus years of patching northeast rust buckets has convinced me to keep things dry as possible. ~ John Buchtenkirch