1976 Dodge Chinook - I've got a question

[RinaBea]

I tried posting this a couple of days ago but it seems to have not gone through so if this is a repeat I apologize.

We recently purchased a 1976 Dodge Chinook and we are in the process of fixing it up. This is the first Chinook that we've owned. While examining the roof we noticed that the channel (unknown function) is filled with a substance that is now rock hard and severely cracked.

We are wondering what the purpose of this channel is?
Does the medium that is inside the channel need to be chunked out and replaced?
If so what does it need to be replaced/sealed with?

Below are a few pictures of the channel and its current state. Thanks in advance for any insight/help.

[SMan]

RinaBea,
First off welcome. I am not familiar with the older Chinooks and really can't give you an informed answer. Look's kind of like a hardened butyl tape or some type of seam sealer. Hopefully someone with more knowledge will chime in.

[chin_k]

Looks like the older Chinook (18 Plus) has the top pieces separately made from the rest, so there is a seam around the top like what you see.

[caconcourse]

I would guess it is probably lap sealant, like this stuff:

Dicor 501LSW-1 Epdm Self-Leveling Lap Sealant

https://smile.amazon.com/gp/product/B00 ... UTF8&psc=1

This is what RV people goop everything with to prevent leaks. If it were me, I wouldn't go to the trouble of digging it out and replacing it if there is no leaking (it seems to be some kind of gutter for water to run off). I would probably brush or clean it with a bleach solution to kill any mildew or mold, and maybe add a thin layer of lap sealant to fill in the cracks and make it look a little better, or just fill the cracks with some plumber's putty.

On the other hand, if it is crumbly and easy to get out, maybe do it. I would test a very small section to see if there is a need or benefit before I did the whole thing. If it is hard to get out and tightly bonded, it is probably still doing its job.

[Zayvier]

I have the same year and model chinook you have. Do you happen to have any manuals for it? Do you know the fresh water tank size? Black tank size? Grey tank size?

Thanks!

[chin_k]

older Chinook manuals are hard to find. Here is one for 1978 on our reference forum, and maybe there are a few things that it shares with the 1976 model?

viewtopic.php?p=9935#p9935

Good luck.

[Catimann]

I also have a 76 for over 10 years and that joint looks just like mine. I have no leaks there and think what caconcourse said is good advice. I have had the large window seal leak and it was not too hard to remove the window (two person job) and to replace it with the same grey sealant. Remanufacturing the inside window frame ( a pc of plywood that goes around the window) was interesting but done with regular tools and glued on with PL4000. I then put a sealer around and over the top of the window called Big Stretch. Supposed to not break and just stretch.

My only leak issue. I have tested other RV's with a big fan and soapy water. force air in a window or door and seal up all the rest as tight as possible to pressurize the vehicle. Then spray on soapy water.