Sealing windows, caulk or butyl tape?

[Piersg]

I'm in the process of stripping down the bus, and before I paint it I'm going to pull out all the windows and refinish them. When I put them back in, is it better to use butyl tape or should I go with some sort of caulk (if so, which one)?

Thanks!

[porkchopsandwiches]

Originally Posted by Piersg

I'm in the process of stripping down the bus, and before I paint it I'm going to pull out all the windows and refinish them. When I put them back in, is it better to use butyl tape or should I go with some sort of caulk (if so, which one)?

Thanks!

Looks like you have a very similar bus to mine. Your windows are held in by the little metal tabs that are screwed in on each side, yes? What I did on mine was pull out all the windows. If you weren't sure how, the best way is to undo all the little metal brackets, score the perimeter inside and out of each window frame with a utility knife to break the current seal, then pull the window in from the top and lift it out.

The stuff that seals it from the factory is some super gooey rubber stuff that at least on mine, was still tacky ~17 years later. I scraped each window frame as well as the frame on the body of all the gooey stuff, bent the little metal tabs so they had a bit more tension on them when put back in, reinstalled the windows and sealed the perimeter inside and out with high grade silicone. Make sure it is pure silicone rated for outdoors, UV exposure, etc. I recommend doing it this way because it got rid of the super loud window rattles and shakes when driving that these buses always have. I probably used 12 tubes of silicone doing this, maybe more. PM me for questions!

[jazty]

I, personally, would stay away from silicone. If ever the window needs to be removed it will be a pain in the arse to clean and re-caulk. There are some very good thermoplastic rubber sealants out there that seal great, stretch far, are made for extreme temperatures AND can be removed in one long piece when the time comes. I experimented with many sealants before settling on Mulco Supra Expert for sealing metal-to-metal.

[Piersg]

Thanks for the info. So far I have one vote for Silicone caulk and one vote against it. I'm sort of leaning towards using Butyl tape because I can get it pretty cheap and it is a little less messier, however I am keeping my options open.

[family wagon]

My 1991 Blue Bird school bus had gray stuff around each window that looked like butyl to me. I now have a 2000 Blue Bird transit bus with a different kind of windows; these were installed with a heavy (stiff) black open cell foam plus gray stuff that looked like butyl.

Perhaps it's due to amateur workmanship such as failure to clean the surfaces with alcohol -- but I've seen many more silicone caulk fails than butyl fails.

[jazty]

My question about butyl tape is this: On my bus the metal that the bus window connects with is perpendicular to the window frame. Does butyl tape work effectively at sealing two perpendicular pieces of sheet metal? It works great when squashed between two parallel surfaces, but my guess is that the sheet metal coming into it at a perpendicular angle would act like a knife going through it. Caulk type sealants are typically meant specifically for perpendicular surfaces.

If the bus originally came with butyl tape then it must be ok, though. Other buses may be built differently.

[Tango]

There are a couple of varieties of automotive Seam Sealer that work like gangbusters. The urethane type comes in several colors, is totally waterproof,never dries out, is paintable in 30-45 minutes, won't shrink or crack and is unaffected by UV and chemicals. And while it is tough stuff can usually be "peeled" or scraped off without too much hassle. The 3M variety is just one of several that are OEM speced by the automakers.

There is also a heavy duty two-part epoxy variety that is a different animal, but very useful too.

PS...Butyl tape is great too, but works best between two smooth, flat surfaces. If there are any variances, the fluid application is better at filling in any voids.

[nat_ster]

Tango said it best.

Nat

[Piersg]

hmm, so now I need to research 3M Automotive Seam sealer!

Thanks for the info guys!

Now, does anybody have a good source for roof hatches? Mine was leaking and when I took it off I found 5 layers of old caulk covering inch long rusted out holes on the edges of the pop up vent. I cleaned it off and recaulked it, but it needs to be replaced.

[nat_ster]

IMO I don't feel roof hatches are needed for a privet conversion. I will be sealing mine with a sheet of steel.

Nat

[charles_m]

I was super happy to have a bus that pre-dated roof hatches. Butyl rubber is great stuff.

[porkchopsandwiches]

Originally Posted by nat_ster

IMO I don't feel roof hatches are needed for a privet conversion. I will be sealing mine with a sheet of steel.

Nat

I kept mine because I wanted to keep a few items to retain the novelty of it having been a school bus and that is one of them. It is nice to pop them up for ventilation as well, I built some rigs out of computer fans to pull a bit of air through.

FWIW I have had no issues with the silicone. None of it has leaked or come loose. My uncle installs frameless shower doors for a living (silicone around the sides of each door) and I used the brand he did, some RTV stuff, which is real high quality and is supposed to last 10+ years. I will agree it is a pain to get off though.

I agree with Tango on the seam sealer. I want to say the seam sealer I used (auto parts store stuff) WAS affected by UV and you had to paint over it, which added a step and is why I went with silicone. I used seam sealer on the holes in the floor + rivets and it worked great. He is right, it is super tough, but if you get it somewhere you don't want it (metal surface or whatever) it is easy to scrape off. Though I have some pants that I got some globs of it on well over a year ago that I wear and wash regularly and there are just as many globs, haha. Based on these suggestions, when I do another conversion, I would go with seam sealer, just make sure it is UV resistant.

Piersg, did you want school bus type hatches or just any old hatch? You can get just any old hatch off ebay pretty cheap. But school ones are harder to find and are expensive when you do find them.

Case in point:

SMART Hatch - School Bus Parts - A Parts Warehouse (great site btw for oddball parts)

School Bus Emergency Roof Hatch Transpec Saftey Vents Transpec | eBay

Here is an alternative that I believe is the same size as a bus hatch but not quite the same: Roof Vent Escape Hatch White Lid Metal Frame RV Bus Heng's 66621 C2 | eBay

(I bought my 46 gallon tanks from this seller).

I got replacement roof hatches from wmkbailey (where did he go?) because he steel'd over his and his were replaced a few years prior to him buying it. Also that lucky sum'b has a like-new engine in his bus but that is another story. I sealed my roof hatches with urethane seam sealer (like Tango suggests with the windows) and I have zero leaks on my bus currently. Though if I did I doubt I'd know because of the way I did the ceiling panels

Good luck!

[Piersg]

Originally Posted by porkchopsandwiches

I kept mine because I wanted to keep a few items to retain the novelty of it having been a school bus and that is one of them. It is nice to pop them up for ventilation as well, I built some rigs out of computer fans to pull a bit of air through.

FWIW I have had no issues with the silicone. None of it has leaked or come loose. My uncle installs frameless shower doors for a living (silicone around the sides of each door) and I used the brand he did, some RTV stuff, which is real high quality and is supposed to last 10+ years. I will agree it is a pain to get off though.

I agree with Tango on the seam sealer. I want to say the seam sealer I used (auto parts store stuff) WAS affected by UV and you had to paint over it, which added a step and is why I went with silicone. I used seam sealer on the holes in the floor + rivets and it worked great. He is right, it is super tough, but if you get it somewhere you don't want it (metal surface or whatever) it is easy to scrape off. Though I have some pants that I got some globs of it on well over a year ago that I wear and wash regularly and there are just as many globs, haha. Based on these suggestions, when I do another conversion, I would go with seam sealer, just make sure it is UV resistant.

Piersg, did you want school bus type hatches or just any old hatch? You can get just any old hatch off ebay pretty cheap. But school ones are harder to find and are expensive when you do find them.

Case in point:

SMART Hatch - School Bus Parts - A Parts Warehouse (great site btw for oddball parts)

School Bus Emergency Roof Hatch Transpec Saftey Vents Transpec | eBay

Here is an alternative that I believe is the same size as a bus hatch but not quite the same: Roof Vent Escape Hatch White Lid Metal Frame RV Bus Heng's 66621 C2 | eBay

(I bought my 46 gallon tanks from this seller).

I got replacement roof hatches from wmkbailey (where did he go?) because he steel'd over his and his were replaced a few years prior to him buying it. Also that lucky sum'b has a like-new engine in his bus but that is another story. I sealed my roof hatches with urethane seam sealer (like Tango suggests with the windows) and I have zero leaks on my bus currently. Though if I did I doubt I'd know because of the way I did the ceiling panels

Good luck!

Thanks for the links. For now I'm going to patch up the roof hatch, but I will eventually replace it down the road, I need to save my pennies for paint and insulation now! Like you, I want to keep the hatches for the look, and I like being able to pop it open for ventilation or to get up on the roof easily.

I'm following your build with a lot of interest, can't wait to see how your underbody storage turns out!

We have very similar buses, I think mine has an extra row and a mechanical Cat 3116 instead of a 3126.

[EastCoastCB]

I love a bus with palm trees in the shot!
I get homesick where there aren't palms. Nice bus and photo!
We have so many floridians on here, I'm gonna have to have a get together SOON.

[Tango]

3M is just one of a number of good brands. If you have access to an auto paint & body supply shop...they will probably have several brands & types.

[nat_ster]

Cleaning surfaces with rubbing alcohol before applying silicone will be the difference between it bonding, and not sticking at all.

The more vinegar smell the silicone has, the better the quality of the silicone.

I learned this from a old friend years ago. He and I renovated many bathrooms and kitchens together.

Nat

[Piersg]

Originally Posted by EastCoastCB

I love a bus with palm trees in the shot!
I get homesick where there aren't palms. Nice bus and photo!
We have so many floridians on here, I'm gonna have to have a get together SOON.

Thanks! Once the bus is semi done we will be using it to camp up in Central Florida, maybe we can get together then.

[Piersg]

Originally Posted by Tango

3M is just one of a number of good brands. If you have access to an auto paint & body supply shop...they will probably have several brands & types.

I will definitely check out an Auto parts supplier, thanks!

[Piersg]

Originally Posted by nat_ster

Cleaning surfaces with rubbing alcohol before applying silicone will be the difference between it bonding, and not sticking at all.

The more vinegar smell the silicone has, the better the quality of the silicone.

I learned this from a old friend years ago. He and I renovated many bathrooms and kitchens together.

Nat

Thats good to know. Do you need to use rubbing alcohol, or can denatured alcohol also be used?

EDITED: I'm a dumbass, rubbing alcohol is denatured alcohol...

[porkchopsandwiches]

Originally Posted by Piersg

Thats good to know. Do you need to use rubbing alcohol, or can denatured alcohol also be used?

EDITED: I'm a dumbass, rubbing alcohol is denatured alcohol...

Yep. That must be why mine held then, haha. And the silicone smelled like you were huffing a bottle of white vinegar.