Newby question - rust around rear window bottom corners

[Rubatoguy]

C-bodies seem to have endemic rust in the bottom rear window corners and near the trunk hinges. Has the cause of this ever been discovered? Is it just a bad design and an area where water tends to sit? How hard a repair is this?

thanks

 

[superfragl]

Looks like the water just sits there, and when it is covered with trim it takes longer to dry.
Took me 2-3 hours per side to fix.

 

[Samplingman]

That's some nice work there.

 

[cbarge]

A bad design. They leaked even when new.
The mid/late 60's was when engineers were moving away from rear window gaskets to Butyl and then Urethane. Add the slope of the trendy "fastback" roof lines, and poor drainage you get rust after a few years. Vinyl top cars get hit even harder since the factory did not even bother painting the roof and rear window area being covered to save money.
Remember when the cars were new,they were slammed out the door quickly as possible and were never intended to last 10,20,or 50 years later.

 

[Pete Kaczmarski]

A bad design. They leaked even when new.
The mid/late 60's was when engineers were moving away from rear window gaskets to Butyl and then Urethane. Add the slope of the trendy "fastback" roof lines, and poor drainage you get rust after a few years. Vinyl top cars get hit even harder since the factory did not even bother painting the roof and rear window area being covered to save money.
Remember when the cars were new,they were slammed out the door quickly as possible and were never intended to last 10,20,or 50 years later.

All will leak sooner or later. I have found cars near the East and West coasts can leak as it rains and any salt in the air contributes to the rain. So the more salt the quicker it may leak in those areas. Years ago someone told me "Coastal cars rust from the top down and midwestern cars rust from the bottom up".

 

[commando1]

I disected mine to find out why.
The engineers designed the butts of sections to overlap, bend 180 and then crimp under.
A physical impossibility to do in mass production. They didn't crimp properly leaving daylight the butts. Guaranteed to leak water.

 

[Big_John]

You have a lot of things going against it. It's in a spot, under the trim, where water and dirt collect. The dirt (leaves etc.) hold the moisture against the body. You also have a spot welded seam the lets water get in the seam. Then, to top it all off, the paint on the underside is minimal at best.

 

[cbarge]

I am no expert, but with some help Ray and I took our time measuring,test fitting over and over. Tough spot tedious to work on but in the end the window fit perfectly.
My glass installer used 3/8" butyl I had, and then with a caulking gun containing urethane for glass sealing, sealed the outer perimeter of the window.

 

[65sporty]

That's some nice work there.

X2, did you use a shrinker to form the curve?

 

[superfragl]

Yep, shrinker than some light hammering to get rid of wavy surface. Tacked in place, installed the glass, trim to make sure everything fits. Took it apart and did final welding.

 

[70bigblockdodge]

Its not just C bodies they all leak there.

 

[Slantsix]

Mopar Muscle Magazine had this.
How To Repair A Rusty Windshield Channel

 

[commando1]

Mopar Muscle Magazine had this.
How To Repair A Rusty Windshield Channel

That's about 10% of making a trunk chanel. Look at making the cross section profile of that and then trying bending it