Exterior and frame rust underneath rub rails

[Domino Joe]

I recently bought a bus with some pretty nasty rust, and I'm wondering what steps need to be taken to properly deal with it. This is my first build and I'm new to all this, so please bear with me.

It looks like the rub rails were not properly sealed and water was pooling behind them, causing rust to eat through the exterior of the bus and some parts of the frame. I removed the rub rails and got rid of as much of the rust as possible from the outside. The attached images show what some of these areas look like now.

For areas where the frame seems pretty much intact, there is clearly surface rust (at least) between the exterior metal and the frame or underlying metal that I can't access from the outside. I assume this needs to be dealt with. How should I go about doing this? Would I cut a rectangular panel out of the side of the bus around the area, clean up/treat the rust underneath and weld a new panel in its place? What tool/method would I use to do this, assuming I want to avoid cutting deeper than the thickness of the exterior metal?

For areas where there are holes in the frame, what is the best course of action? Could I just eliminate and treat the rust to keep it from spreading, and then add some kind of reinforcement? Or do these sections need to be replaced entirely?

My father-in-law is basically telling me to just hit whatever I can reach with a wire wheel, prime it, patch everything with fiberglass, and call it a day, which I'm assuming is not the advice I'm going to get on here. What are the consequences of doing it his way?

[peteg59]

Not to discourage you Joe but unfortunately, what hidden rust you don't see is usually much larger and severe than what you see on the outsides once you really "dig in".

I will always try to steer clear of any prospective vehicle I'm interested in that has lived its life up in the country's "Rust Belt", and would encourage anyone else to do the same.

Hopefully your bus is not cancer/rust ridden to the point of it costing more to remediate, than it would be worth.

Having said all of that, it really depends now on what you plan on doing with the bus.
Are you doing a camper conversion and plan on keeping it long term?
Or are you simply looking to cover up the visible rust and run with it until the structural integrity of the bus deteriorates to the point of it being unsafe for the road as your FIL suggests?

Best of luck to you on your project, if you go forward with it...

[musigenesis]

I'm not familiar with Collins bodies, but it seems like all that exterior body damage is on the line of the interior floor. It's common for buses to rust from the inside out, so you may be looking at internal floor rust that made its way through to the exterior skin. Have you demoed the inside yet?

Rub rails usually have little pressed channels on the bottom that allow any water that gets inside them to drain out, so I'm not sure what you're looking at is a case of the rub rails causing the rust. More pictures of everything would help to diagnose your situation.

For any kind of long-term repair, you will need to cut out any hopelessly rusted metal (which might be quite a bit) and weld in replacement structure and sheet. What your FIL is suggesting is Temporary with a capital T.

[Domino Joe]

Originally Posted by musigenesis

I'm not familiar with Collins bodies, but it seems like all that exterior body damage is on the line of the interior floor. It's common for buses to rust from the inside out, so you may be looking at internal floor rust that made its way through to the exterior skin. Have you demoed the inside yet?

Rub rails usually have little pressed channels on the bottom that allow any water that gets inside them to drain out, so I'm not sure what you're looking at is a case of the rub rails causing the rust. More pictures of everything would help to diagnose your situation.

For any kind of long-term repair, you will need to cut out any hopelessly rusted metal (which might be quite a bit) and weld in replacement structure and sheet. What your FIL is suggesting is Temporary with a capital T.

Okay, based on your insight I did a little more digging. The exterior rust is actually about 3 inches below the floor level. The interior is gutted down to the metal floor, which does have rust, but nothing quite as nasty as what's outside, and nothing that matches up significantly with these areas. (Most of the damage you see in the picture is from me - I had to use a sawzall to cut the bolts securing the seat tracks to the floor, and the sheet metal is really thin, so I ended up cutting a hole in the floor on pretty much every bolt. My plan at this point is just to replace this sheet metal entirely.)

I don't know if this is a common design or not, but it looks like that metal on the lower portion of the wall forms a chamber with the exterior metal, which is filled with fiberglass insulation, and extends below the floor to right where this rust is showing up. There's a lot of rust on the window sills as well, so my assumption now is that water was entering through the windows and getting trapped behind the wall panels. Thoughts?

[musigenesis]

Originally Posted by Domino Joe

I don't know if this is a common design or not, but it looks like that metal on the lower portion of the wall forms a chamber with the exterior metal, which is filled with fiberglass insulation, and extends below the floor to right where this rust is showing up. There's a lot of rust on the window sills as well, so my assumption now is that water was entering through the windows and getting trapped behind the wall panels. Thoughts?

That sounds exactly right. If you can stop the windows from leaking, you can then repair the external skin by cutting out the rusted parts and welding patches in place (followed by some bondo work). You could even rivet the patches on, which would get you out of having to worry about heat-warping the thin skin with welding. Personally, I think stuff riveted on to the outside of buses looks perfectly normal given how many rivets there already are on a bus.

[Domino Joe]

Originally Posted by peteg59

Not to discourage you Joe but unfortunately, what hidden rust you don't see is usually much larger and severe than what you see on the outsides once you really "dig in".

I will always try to steer clear of any prospective vehicle I'm interested in that has lived its life up in the country's "Rust Belt", and would encourage anyone else to do the same.

Hopefully your bus is not cancer/rust ridden to the point of it costing more to remediate, than it would be worth.

Having said all of that, it really depends now on what you plan on doing with the bus.
Are you doing a camper conversion and plan on keeping it long term?
Or are you simply looking to cover up the visible rust and run with it until the structural integrity of the bus deteriorates to the point of it being unsafe for the road as your FIL suggests?

Best of luck to you on your project, if you go forward with it...

Thanks for the feedback. I'm pretty comfortable moving forward with the project even if my bus's days are numbered. This is my first conversion, I'm going to make tons of mistakes, so I'll probably want to move on to something else in a few years anyway. I mostly just wanted to see if it made practical sense to try and deal with this rust properly.

I did do my research beforehand, so I knew that buying a bus in the Northeast meant I was going to be dealing with rust. I also knew how strongly this community recommends against it, but it just didn't make any logistical or financial sense for me to try and get bus from another part of the country, especially during quarantine, and I made a conscious decision to move forward anyway.

That being said, the rust that I'm asking for advice about doesn't seem to be related to road salt at all, but rather from a combination of bad seals and rainwater, which I reckon could happen in any part of the country, so where I bought it from is kind of a moot point, right?

[Domino Joe]

Originally Posted by musigenesis

That sounds exactly right. If you can stop the windows from leaking, you can then repair the external skin by cutting out the rusted parts and welding patches in place (followed by some bondo work). You could even rivet the patches on, which would get you out of having to worry about heat-warping the thin skin with welding. Personally, I think stuff riveted on to the outside of buses looks perfectly normal given how many rivets there already are on a bus.

Cool, I like what I'm hearing. Riveting the patches on does sound a bit more my speed. I might look into mounting an underbody toolbox right where the really big gash is on the passenger side. I'm sure its not any less work, but it would be nice to have and I'd end up with some spare clean metal I might be able to use to patch up some other areas.