Re: Larry's 1951 Club Sedan Project
Posted by Larry51 On 2011/5/14 4:13:41
Removal of Old Seam Sealer Around the Turret
The body was grit blasted and in many areas the old seam sealer and dum-dum was blasted away. In some places only limited blasting was done, to avoid panel distortion, so the old seam sealer remained, especially around the gutters of the roof (turret).
After removing some of this old sealer and dum-dum it was found that a small amount of rust was present in some areas, and surface rust was present almost everywhere under the sealer. Seems back in those days Packard didn't prime the metal before sealing the seams.
I'm obsessive about getting rid of rust, so wanted to give the car the best possible treatment so nil rust can remain or return later.
It took a couple of days of tedious work to remove the sealer which was a hard rubber compound. In some areas I used a heat gun to soften it and it melted fairly easily. Then it could be scraped out with various implements such as a ground hacksaw blade, scribers, bent screwdriver blades etc.
Never used heat guns much in the past but now I'm finding them totally great! Many uses already, like heating panels prior to filling or spraying . . . more about that later.
Sealer had penetrated well into the joins so it was also softened by applying lacquer thinners with a small artist's paint brush. Then it could be removed more easily. The final process was to double over a piece of 240 wet and dry and continually rub it along the join, edge on. This got well into the joints of the gutter - turret and removed almost all the old filler.
I was lucky - there was no serious rust anywhere along these seams, with only one hole found in the entire length of the gutters.
The seams were treated with Deoxidine from both sides (- I could get to the gutter seams from inside the car as well) then primed before applying the new sealer. Two coats wet on wet of something very fluid and slow-drying that can be applied by brush I considered to be a much better option than a quick-drying (air drying) sprayable primer, which might not penetrate into the seams as well. Better to use a slow-curing primer so it has time to get right in, and fully seal any rust there. So it was POR-15 I used. It'll seal the metal super well, and there's no problem over-coating it.
I reckon you've got to get the gutters totally water tight and rust-proof.
Most pre-1970's cars had seams that were visible and the sealer used formed a visible 'line' along the seam, described as a "visual definition seam'. 3M Heavy Drip-Chek is designed to reproduce these visible seams. Doesn't sag, and because it shrinks considerably, you create a bead that is larger than the final seam thickness needed. The Drip-Chek then shrinks (a lot) and gives a neater final result as any imperfections and slightly uneven thicknesses also shrink making the new seam look pretty good.
Instructions say make the bead bigger than required to take into account the shrinkage. The Heavy Drip-Chek can be painted over when dry. You can also add more over existing Drip-Chek if necessary, it bonds really well. You must prime the seam before using the sealer - something Packard didn't do on my car.
Next product recommended as a good replacement for original dum-dum is also from 3M. Inexpensive and very easy to use, 3M Caulking Strip comes as a box full of strips and can be painted over. In many seams it will be easier and more effective to use Sikaflex HS-227 (cartridge application).
Here are a few 'before and after' pics of the work done . . . .
Not too bad for rust . . . just a small amount under where the old sealer was placed
Some minor rust forming along the gutters . . .
. . . and the worst place was at the rear section where water would linger longer
Small surface rust up and under the gutters also, where it formed on the 'unprimed' metal
The gutter cleaned and roughed with 60-grit, ready to take the POR-15 sealer (2 coats).
POR-15 painted into the gutters. This stuff is hopefully seeping right into the cracks and forming a total barrier to water.
The front pillar will get the same treatment
The body was grit blasted and in many areas the old seam sealer and dum-dum was blasted away. In some places only limited blasting was done, to avoid panel distortion, so the old seam sealer remained, especially around the gutters of the roof (turret).
After removing some of this old sealer and dum-dum it was found that a small amount of rust was present in some areas, and surface rust was present almost everywhere under the sealer. Seems back in those days Packard didn't prime the metal before sealing the seams.
I'm obsessive about getting rid of rust, so wanted to give the car the best possible treatment so nil rust can remain or return later.
It took a couple of days of tedious work to remove the sealer which was a hard rubber compound. In some areas I used a heat gun to soften it and it melted fairly easily. Then it could be scraped out with various implements such as a ground hacksaw blade, scribers, bent screwdriver blades etc.
Never used heat guns much in the past but now I'm finding them totally great! Many uses already, like heating panels prior to filling or spraying . . . more about that later.
Sealer had penetrated well into the joins so it was also softened by applying lacquer thinners with a small artist's paint brush. Then it could be removed more easily. The final process was to double over a piece of 240 wet and dry and continually rub it along the join, edge on. This got well into the joints of the gutter - turret and removed almost all the old filler.
I was lucky - there was no serious rust anywhere along these seams, with only one hole found in the entire length of the gutters.
The seams were treated with Deoxidine from both sides (- I could get to the gutter seams from inside the car as well) then primed before applying the new sealer. Two coats wet on wet of something very fluid and slow-drying that can be applied by brush I considered to be a much better option than a quick-drying (air drying) sprayable primer, which might not penetrate into the seams as well. Better to use a slow-curing primer so it has time to get right in, and fully seal any rust there. So it was POR-15 I used. It'll seal the metal super well, and there's no problem over-coating it.
I reckon you've got to get the gutters totally water tight and rust-proof.
Most pre-1970's cars had seams that were visible and the sealer used formed a visible 'line' along the seam, described as a "visual definition seam'. 3M Heavy Drip-Chek is designed to reproduce these visible seams. Doesn't sag, and because it shrinks considerably, you create a bead that is larger than the final seam thickness needed. The Drip-Chek then shrinks (a lot) and gives a neater final result as any imperfections and slightly uneven thicknesses also shrink making the new seam look pretty good.
Instructions say make the bead bigger than required to take into account the shrinkage. The Heavy Drip-Chek can be painted over when dry. You can also add more over existing Drip-Chek if necessary, it bonds really well. You must prime the seam before using the sealer - something Packard didn't do on my car.
Next product recommended as a good replacement for original dum-dum is also from 3M. Inexpensive and very easy to use, 3M Caulking Strip comes as a box full of strips and can be painted over. In many seams it will be easier and more effective to use Sikaflex HS-227 (cartridge application).
Here are a few 'before and after' pics of the work done . . . .
Not too bad for rust . . . just a small amount under where the old sealer was placed
Some minor rust forming along the gutters . . .
. . . and the worst place was at the rear section where water would linger longer
Small surface rust up and under the gutters also, where it formed on the 'unprimed' metal
The gutter cleaned and roughed with 60-grit, ready to take the POR-15 sealer (2 coats).
POR-15 painted into the gutters. This stuff is hopefully seeping right into the cracks and forming a total barrier to water.
The front pillar will get the same treatment
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