What is this hole in the floor?

[Thetireddad]

Hi everyone,
I have a random hole underneath the rubber flooring of the bus. It appears to be around the fuel tanks. Should I seal it up? Any idea what it is for?

[JDOnTheGo]

I'm guessing that is your fuel level sensor (or a sensor for something) and the hole is the only access to it. You can seal it up but if you ever need to access it in the future... well... it'll be a problem.

My life experiences have taught me that you never need to touch a thing as long as it is easily accessible. As soon as I make something difficult to access, I need to get to it!!

[Rivetboy]

See the wires in the hole? That is access for the fuel sending unit. If you do cover that hole be prepared to drop the tank if you need to replace the fuel sending unit. Or, be proactive and replace it now and then cover the access up. Sending units are fairly inexpensive.

[Thetireddad]

Thanks guys!

[gs1949]

Yeah, it's definitely for accessing the fuel tank. My Bluebird has a hole like that in the floor, and there was a hole in the original plywood too. The hole was only covered by the vinyl flooring and a metal cover screwed in place on top of the vinyl, so it was obvious no one ever felt the need to access the tank through that hole. I plan on building a water resistant hatch, and then a cupboard with an easily removable bottom.

[Danjo]

What are you going to install in the bus in that spot? If it’s a cabinet, maybe you can just make a cover for it and make it accessible later. I can imagine dropping the tank would be a bit of a PITA, but with a bus at least you wouldn’t need to jack it up

[HazMatt]

More than a bit of a PITA, if, like mine, there's a crush cage enclosing the tank.

[gs1949]

@Danjo, yeah, that's the great thing about working on buses. I gave up working on cars some years ago when my back started bothering me a bit because they were just too low. But there's plenty of room under the Bluebird.

[o1marc]

I checked on mine to see if the sensor was accessible from under the bus, and while it may be a PITA, I figured that access hole has probably never been removed yet and the covering of it was less critical than I think. I never heard of tank sensor issues like Im have other common issues on buses.

[gs1949]

Yeah, you're right. I don't remember reading much about problems there, but I have read at least 2 threads here that contained warnings that covering it up so that acceess was difficult would be unadvisable.

I could tell when I started removing the floor that mine had never been accessed, so I intend to cover it up but still have it accessible without tearing up anything.

[o1marc]

Originally Posted by gs1949

Yeah, you're right. I don't remember reading much about problems there, but I have read at least 2 threads here that contained warnings that covering it up so that acceess was difficult would be unadvisable.

I could tell when I started removing the floor that mine had never been accessed, so I intend to cover it up but still have it accessible without tearing up anything.

I covered mine with insulation and flooring. In the event I would need to access through there it would not be a big deal to cut the square out , after removing any furniture or cabinet over it.

[gs1949]

Yeah, if you can find it exactly. I think I'll do the cutting before I need it, and it's exactly where I want my kitchen counter, so having a little hatch there won't cause any problems.

[musigenesis]

Is it generally bad to let crap pile up inside that hole? Mine had a crude (presumably aftermarket) patch screwed over it which came up with the plywood. I've generally tried to keep it covered since then, but at various times dirt and screws and small demo bits have gotten down there.

[gs1949]

Maybe your's was opened at some point. Mine was obviously patched at the factory and had never been opened. I could tell that because there was a hole in the plywood, but no hole in the large piece of vinyl that covered the whole length of the curbside of the passenger compartment. And there was a small, square piece of fairly heavy gauge steel screwed over the vinyl.

I have not driven the bus since I exposed the hole, so I don't know for sure about road noise, but without that heavy vinyl it lets in a lot of engine noise. So I want to cover it with something to get more quiet back.

[HazMatt]

Musigenesis:
If you have an inopportune screw loose, I suppose it could short the fuel sender out if it landed on both contacts.
Next time at WaWa, get an appropriately sized Slurpee, and put the empty in the hole, in the interim...

[musigenesis]

Originally Posted by HazMatt

Musigenesis:
If you have an inopportune screw loose, I suppose it could short the fuel sender out if it landed on both contacts.
Next time at WaWa, get an appropriately sized Slurpee, and put the empty in the hole, in the interim...

I wonder if I shorted out the vandal lock thing in some way. Whenever I forget to open the deadbolts on the exit doors (which is every frikkin time) I get the same lack of starting up. I jiggled the heck out of them in the Wawa lot but that didn't affect anything.

[musigenesis]

Originally Posted by gs1949

Mine was obviously patched at the factory and had never been opened. I could tell that because there was a hole in the plywood, but no hole in the large piece of vinyl that covered the whole length of the curbside of the passenger compartment. And there was a small, square piece of fairly heavy gauge steel screwed over the vinyl.

Hmm, that actually describes how mine was put together as well, so maybe it wasn't part of a repair. The square plate on mine was heavily corroded which is what made me assume it was a spotty repair. The hole is also sufficiently corroded that I couldn't tell if it was a factory hole or not.

[gs1949]

Yeah, my cover plate was a little rusty on top too, but that was just because it's pretty close to the 2 leakiest windows. The lack of a hole in the MLV was what convinced me it had to be from the factory that way.

I still have all that MLV I pulled up and I intend to use some of it, at least 2 layers, in the cover I intend to build. That should eliminate most of the noise coming through the hole when I start the engine.

[Kegger]

Like everyone said it is to access the sensor. When we did our build, we made sure this was accessible by making sure the cabinet above could be moved. Thankfully, when we had a fuel tank issue, the tech could easily get to the sensor and replaced it. Would have been expensive to drop the entire tank.

[ABdriver]

Besides the fuel sender, if the tank ever has to come out a lot of buses
use that hole to reach through and disconnect hoses too. Otherwise you stretch and damage them. Leave it accessible!