Hi all,

Does anyone know what the substance is that was applied between the front fenders and the inner fender aprons (Sally - 1966 F100 2WD)? It was also between the front of the inner aprons and the radiator core support.

What is the purpose? noise/vibration control? sealer? etc.

The stuff looked kind of like and had the consistency of the 3M strip caulk (dum-dum).

 

It is caulk, my Ford manual calls for "caulking cord" between the inner fender and fender. I am not sure about the other places.

I saw some white flat caulk strips in the bathroom construction area at the local stores. Right or wrong, I used some black sealer tape I got from an ac guy. It is used for sealing the gaps around the ac lines.

Caulk can not hurt if applied so there is less chance of collecting and holding moisture but if applied wrong..... you are asking for trouble so be smart about how you apply it, avoid creating water traps and low spots. This is easier said than done.

 

I used seam seal that was supposed to *not* harden. It hardened and did not allow the seal to close evenly. I am in the process of scrapping it off (one step forward, 2 steps back). I will be using Butyl tape that can be purchase at any RV supply store or online.

 

Here's a link to some butyl rubber in 15' lengths. This is about 1/3" thick stuff. My Dad always had a roll of this stuff around.

Bulk3

 

Thanks for the replies. Will the butyl rubber stuff spread out nicely when the parts are cinched together with the bolts? I know the caulk strip stuff will, but just as OBP stated it must be applied with care to avoid the voids.

 

AB-19560-A (Rotunda R-135-A) / Pic from 1948/56 truck parts catalog. Same caulk listed in 1957/63, 1964/72, 1973/79 truck catalogs, but there's no pics.

 

The caulking used never spread out evenly or consistently...its an anti squeak/rattle item moreso vs a sealer...the stuff does harden to almost rock hard over time...most rigs Ive taken apart though didnt have any used in the front clip except between the fenders and the apron...they were usually metal to metal where the aprons join the core support...electrical grounding ability...It is dum dum thats used...


- cs65

 

CS65, That is interesting, this stuff was still pliable and easily removed with a putty knife followed by a low effort rub with a mineral spirit soaked rag. Someone else must have refreshed the stuff somewhere along the line I suppose, or maybe in the humidity of the southeast it remains pliable.

Bill,
I searched the Rotunda name and numbers, but not much out there (this thread is in top 3 google results). Best I can figure from what I could find is the product is no longer available and a 3M product called strip-caulk # 08578 is what is being employed as a substitute (I think this is what is called dum-dum by many). One source having a brief description of the Rotunda product stated it contained asbestos

 

Bill,
I searched the Rotunda name and numbers, but not much out there (this thread is in top 3 google results). Best I can figure from what I could find is the product is no longer available and a 3M product called strip-caulk # 08578 is what is being employed as a substitute (I think this is what is called dum-dum by many). One source having a brief description of the Rotunda product stated it contained asbestos

Your truck has now killed you.............PS: it is also in all the seam seal brushed on the seams in side the cab and in the sealer in the roof gutters. It is even in the bondo between the cab roof panel and sail panel. a literal friable rolling hazmat... in the 60s it was still a miracle substance.

Use 3 M strip caulk if you ever want to get it apart again. The butyl rubber stuff is a bear to get apart.

Garbz

 

garbz2,

Thanks for the heads up regarding the widespread use of carcinogens. I cleaned all those seams out in the cab interior using a wire brush on a drill before resealing while wearing just the cheapo dust mask . Not dead yet, but sure that did not help my future prospects for longevity. When I do the other 66 I will seek better protection.
I need to use a small dremel flat wheel to remove the cracked sealant/caulk/whatever the hell it is in the seam between the cab lid and the B-pillars on the outside from drip rail to drip rail wrapping around the back of cab. The original stuff is cracked badly and water seeps into the interior in a few spots during hard rain. Do you know what that stuff is and whether it requires a Haz-Mat suit for removal? Thanks.

 

The stuff in the cracks is asbestos reinforced polyester resin. AKA bondo. Ford placed this before spot welding and as the weld was made it squished out uniformly forming the little bead.

I use dental picks and a ground on screw driver to thin it to remove it in chunks. Replacement gets a bit trickier as it is damn near impossible to get the slight half round crown bead. I have had success with ever coat euro-fill polyester glazing putty and a plastic pick nick knife cut a flat edge on it with a bead of the approximate side you need dremeled in to it at about a 30 degree angle. Clean it well with a wire wheel wipe it down with acetone and make a small batch. Work it in with the knife and then pull the bead at the angle you cut in the flat knife edge.

Bondo squeegees are a bit to limber to push in and make the bead. Key is to force it in to the gap so it adheres.

You can then use some fine grit sandpaper to slight edge and take off the ridges.

Seal the inside of the cab with some paint to keep moisture from working back out.

Figure a few days to do it as it is a pain and tedious.

Garbz

 

Thanks Garbz, I will take a swing at those seams following your outline if we ever get a forecast without rain for two consecutive days.

 

Wow, I bow to your knowledge and dedication. This is why I keep telling myself I have a daily driver, not a show truck. I would not be able to see a 30 degree angle in a seam much less "pull the bead at the angle...". The problem with knowing your trick is the next car show I go to, I will be critical of the seams.

Now I am embarressed I let some paint over spray onto my tires as I was too lazy to dismount them when spraying the steel wheels. I am going to have a 1 ft. paint job (until the first major scratch) but the rest of the truck is going to demand a 10 ft. viewing space. This is why the difference between a daily driver and a show truck is 500 hours and $15,000 (at least).

Thanks for the post, I wondered how the old and new seams were done.

 

Most just weld the seam closed and mud it up. All depends what look you want. Stock factory ford paint job was a ten footer. I like beating up on a fully restored uni or wrong beds where all the factory spot welds were removed.

Pulling the bead at an angle means having the knife at 30 degrees to the work surface. You place the pattern cut at an angle in the tip so when you are at the correct angle you get a nice level round bead in the material.



Garbz