Rust never sleeps...

[Delia]

There was discussion a few weeks ago regarding plugs in the rear wheel wells and whether plugging them contributes to rusty rear shock towers.

Here's the trunk section (inner wheel house) of a '72 that has plugs installed in the wheel wells. Not sure if they are factory-installed or not, but the obvious rust-through shown in these pictures seem to reflect a worst-case condition.

Delia

[nbcbird]

I used expanding polyurethane foam (used for home insulation) to seal the cavity and minimize rust.--Jim

[jerry]

are you referring to the plastic cap on the forward edge of the upper spring housing of the rear wheels as viewed from inside the wheel well?

if i remember correctly, the rear seam of that housing has a clearance, presumably to drain water.

i'd suspect that if it is clogged, problems will ensue as water is tossed all over and will find its way in and grit and debris will act as a sponge.

this is similar problem that occurs on the lower front fenders where grit collects.

modern cars seem to address this problem using plastic shields (a prophylactic of sorts) to protect the nooks and crannies from water slurry tossed by tires.

[jerry]

I used expanding polyurethane foam (used for home insulation) to seal the cavity and minimize rust.--Jim

have you kept a close eye on it? how's it holding up? how many winter's has your application endured? sounds like a possible fix as long as water doesn't seep in by capillary action.

[bluedevils]

One of my cars has no plugs and still rusted at similar places. Plugging the holes might help only if the entire cavity is dried and sealed properly. It would make sense to me to cut small holes (even in seemingly good shock towers) in the shock towers inside the trunk and passenger cabin to clean any surface rust, dry and seal the cavity and weld the holes back, just to make sure.

[Delia]

Unfortunately, once the rust has begun inside these sections, it will continue until it's neutralized with POR-15 (or similar), or it just rusts-through. Though round holes may or may not have plugs, the holes at the corners should be kept open. It seems from my cursory investigations and from other owners, that early cars (roundies) had plugs installed at the factory while squaries did not. Rustproofed roundies AND squaries (like Ziebart, Tuff-Coat) HAD plugs. Depending on the technician, they had lots of other plugs where they filled these boxed-in sections with gooey, black tar stuff.

Regardless, keeping it dry is also a good idea. Even high humidity can contribute to the oxidation process.

Mobile Tradition offers patch panels for these sections of the rear inner wheel houses that includes the box and shock tower tube.

Depending on how severely your car is rusted, such a patch might be worthwhile. instead of replacing the entire inner (and possibly outer) wheelhouse.

Delia

[nbcbird]

I thought the cap was on the rear side of the spring mount (22mm size cap). After about 10 years I can detect no rust or deterioration. The area was throughly treated with rust preventative and cavity sealer (spray wax) before foaming. In performing this procedure, I also drilled a small hole into the wheel well cavity from the interior of the vehicle (with the rear seat removed). This allowed for expansion of the foam and also helped as an indicator for achieving maxiumum fill.--jp

[JackF]

Delia, would you please drop me a line at jackfre at verizon dot net? Tanks!

[M3M3]

actually there are two. one in front of and one behind the shock tube.