very 4104 (maybe 4106 specific) re: changing air tank.

[zubzub]

My bus came with a leaking front air tank. The one in front in the middle just aft of the stairwell (not the one that is accessed through the tool storage area).   I already have a spare that I pulled but I just cut that one out, and today I cut the old one out of my bus.  The problem is it's tight in there and there is a line that goes almost straight up through the floor that connects in the middle of the top of the tank.  I have not destroyed anything (yet!) but I think the best way to get this back in is to disconnect the other end of the line (it's small maybe 3/8) so I have enough slack to attach it to the tank.  I think this line goes to the air gage (not sure) but it definately goes straight up just aft of the stairwell.  My bus has a plywood floor, is there any chance there used to be an access opening in the floor ( the line goes up about 12" left of the center line of the bus).  I have looked at the manual and can't really see how to get at this line.  I know changing this tank is not a usual thing so maybe no one knows of what I speak but any suggestions are appreciated. 
BTW this air tank has the same dimensions and ports as the one in the tool storage so with the right fittings they are interchangeable, this is handy as the one I pulled was also a little rusty, but while I was pulling that one I pulled the tool storage tank for a back up and it was nice and had the benifit of being regularly drained so is in much better shape.

[buswarrior]

Do not hesitate to extend or replace the lines with DOT plastic line.

A lot of the heritage copper and brass fittings will simply not cooperate with the busnut intent on faithful re and re, never mind the contortions required.

And the plastic is just so much easier to work with.

Be sure to secure in order that it doesn't rub on anything, or you get to do it again later!

happy coaching!
buswarrior

[gus]

Zub,

I'm pretty sure that line goes to the heating thermostat which is accessible through the right hand side floor vent. I've been in there a few times but can't remember exactly what is what. Look closely in the manual at your air diagram again and you may see how it is connected.

The air gage line is supposed to go from the aux tank, the one in the LH tool compartment.

The original bus interior heat was controlled by a thermostat (It has some other name I can't remember) which controls the air pressure to a valve which opens and closes a water valve and there is a small air line going to it from that front tank. You can also access part of this system through the plywood doors about a a foot inside the RH front compartment just ahead of the fuel tank. All this stuff may have been ripped out of your bus but mine is still intact. If yours is missing the air line is probably plugged since it serves no other purpose that I remember.

What I'm saying is that unless you are using the original bus heating system that air line goes to nothing - unless a PO has hooked it to something else. Otherwise, my guess is that it is capped off.

Look in the heating section of the manual and you will probably find more photos or drawings that will help.

Look also in the air section but you probably have already looked there.

That is good information about the two front tanks being the same, that never occurred to me!! Now maybe I can find a good used one that is not so hard to remove. I know that my other one may rust through any time even though I have a manual drain valve with a long pull cord on it. It didn't have one when I got the bus.

I'm not looking forward to the day I have to change that tank. Changing the rear "wet tank" was bad enough!!

[roadrunnertex]

Gus,
It's called a Gradustat that controls the heater control valve.
jlv

[zubzub]

Changing the rear "wet tank" was bad enough!!
[/quote]


Gus re:the rear wet tank.  Guess what? mine does not seem to be connected to the air system.  I was draining the wet tank for the 1st time (I know I know but the valve didn't work so I was waiting for a safe time to pull the whole assembly).  Well I pulled the whole big nut and the tank had no gunk in it, and when I aired up the bus with the valve out it developed pressure as usual but no pressure in the wet tank.
Not to pleased about this although with luck some PO has taken it off line as the drain valve is shot.  Might explain why the front tank rusted out as well, although the difficult access to the front tank pretty much assures that it won't get drained enough.  I will be installing some kind of rip cord for the front tank,  Since it looks like I need a new valve for the wet tank I wondering if the is some kind of low profile quick drain set up for the wet tank.  It seems unlikely as the valve is right behind the wheel at street level and anything that sticks out would easily be damaged....come to think of it I think I'll stay with the old system for the wet tank.
Thanks to everyone for the info.

[gus]

John,

Thanks, I knew it was something like that but was too lazy to look it up! Do you still have that beautiful 4107? Or is it an '08?

Zub,

Same story for my wet tank, it had been bypassed by using four elbows. I loved the engineering of that original big brass drain but it is a pain to open without getting gunk all over your hand.

Funny thing was that I couldn't tell the tank was missing from the system, I never had any problems with not enough air - ever!! The only difference I can tell now is that the air supply lasts quite a bit longer before it goes down.

My drain valve was OK but the tank was full of pinholes. I'm pretty sure yours has the same problem. If the problem had been only the drain valve that would have been easier for the PO to replace than to bypass the tank. I found my new tank on ebay for around $60. The price for the tank from one of the bus suppliers was around $300 including shipping.

I still haven't been able to find a dry tank on ebay because it is so small and/or can't find one with the larger ports for the main air line.

I have an automatic drain valve installed on my new wet tank and even though it is quite a bit longer than the manual truck type valves it doesn't stick down enough to be a problem. Since it is so close to the rear wheel it is not exposed to damage like it would be if midway between the wheels. Also there is supposed to be sheet metal shield below the tank with a 3" hole for the drain valve.

As I remember there is some latitude in the vertical location of the tank so that he valve height can be adjusted. My tank bottom is slightly above the shield hole to keep the valve as high as possible.

[zubzub]

Gus, glad to hear I'm not the only one.  I was kind of concerned when I realized i had been running without a wet tank.  You're probably right about the reason for by pass.  You mentioned you found a "new" one on ebay.  Was it really new (or new old stock) cause pulling one another 4104 doesn't sound like a good idea.  Speaking of which who knows which  of the GM buses have a tank that fits this application?  I have a decent bus srap yard available to me would be cool if the eighties transits had something to offer.

[buswarrior]

OH DEAR!!!!

Please, if your tanks have been bypassed, get a fresh tank and get the intended capacity back!

Yes, everything is ok, until something goes wrong...

Without the reserve of the wet tank, having some sort of air failure in a rubber part may put you into danger of little to no braking as the relatively smaller capacity of the service tanks is quickly dumped overboard through the new failure point, and the compressor will not keep up.

The wet tank's volume at least gives you more time before the calamity point.

Quite frankly, I would call whoever bypassed those tanks a fool or a villain.

Get those systems back up to capacity, please!

happy coaching!
buswarrior

[RJ]

I wholeheartedly agree with BusWarrior on this one!

We're talking SAFETY ISSUES here - do NOT scrimp in this department.

Just about any air tank will work, even one off an 18-wheeler.  Just get one approximately the same (or LARGER) overall dimensions.  Since you're after a "wet tank", which is usually the closest to the compressor, more than likely searching for a wet tank on other buses or trucks should yield one with similar sized fitting requirements.  Fittings can be adapted to the new tank, but try to find a tank with approximately the same size, first.  IIRC Weatherhead is one brand of brass fittings that come in all shapes and sizes.  NAPA or any really good auto or HD truck parts house (more likely a local, rather than PepBoys, AutoZone, etc.)  Even an older, mom & pop hardware store that's been around forever can be a good source for fittings.

And while you're at it, you might consider adding a Bendix Air Dryer to the system, well worth the investment in clean air!

Again, don't compromise the SAFETY of your coach!!!

FWIW & HTH. . .

[zubzub]

BTW I never intended to run without a wet tank, I only discovered it was off line yesterday.  Might even buy a new one if they have them at NAPA.  Have to pull the old one to get the dimensions.

[gus]

Zub,

In spite of the alarming posts above I ran the 4104 a couple of years before I discovered the tank was bypassed and never came close to running out of air. I crossed the Rockies, among others, at least four times with no problems. Like you, I had no clue it was bypassed because the bypass elbows were right along side the normal connecting ports and were impossible to see. It was only when I decided to try to unplug the drain valve that I discovered the problem. Of course it wasn't plugged at all, there was no air in the tank!!!

I'm not saying run without it, I'm just saying it is not the sky falling in.

The tank I got is new or maybe slightly used, can't remember for sure. But it is like new. It is not a NOS bus tank, as I remember it was made for some kind of automobile system, I think for one of those "jumping" thingies. It doesn't have to be a bus tank, just look for one with the approximate dimensions and correct size ports. The ports can even be oversize if reduced with bushings. Measure the tank and go looking on ebay, that's what I did. The one I got even has a couple of extra ports which I plugged.

You can't use a larger diameter tank because the clamps won't fit and the clamp holes won't line up. Longer or shorter or a slightly smaller diameter should work but you will need to use shims if a smaller diameter.

There is almost no chance you will ever find a used wet tank worth installing. If it is the slightest rust pitted on the outside you are wasting your time because the inside will be much worse. I tried welding, ha, that was a waste of time also. I was told on this board it wouldn't work but thought I would give it a try.

I also installed new clamps, mine were about rusted through and this is the time to replace them unless they are in excellent condition (highly doubtful). I don't remember exactly where I got the clamps but can find out if you wish. This is a real hole to work in. I ran the rear wheels up on two gravel piles which made life much simpler.

[zubzub]

thanks as always nice to know I'm not the only one getting dirty on a 4104.  Below is a pick of how it looks to change a front air tank in the snow....FWIW I lie on a packing blanket and use plastic sheeting  as a slider.

[johns4104]

Gus,
I welded up my wet tank on my parts bus before I towed it home and it worked fine.
As far a the tank straps I used 36" all thread and bent it around the tank (5/16-24).
I also made new aluminum cradles to hold the tank.
By the way this is much easier with the floor out.

Here is a pic of the old cradles and straps.
as well as new straps
ps. the air line for the Gradustat that controls the heater control valve comes from the rear of of the bus.

John

[johns4104]

Zub,
Looking at your pictures makes me so glad the I moved down here (AZ) from Michigan.
That sure looks cold and wet yuk!

John

[buswarrior]

Yes, there is no sky falling, as long as you don't blow a line or a diaphragm.

Yes, for normal functioning, having the capacity of the wet tank bypassed won't cause any "difficulty".

Gus, not to be rude or inflammatory, but you drove your bus for how long without knowing an air tank was permanently empty???

All that air capacity was not installed for normal functioning, it was installed to compensate for a reasonable amount of failure.

RJ and I are not known on these boards to cry Chicken Little ditties.

A bypassed wet tank means a great deal of danger under an air system failure, especially in a single circuit brake system. The smaller supply of air will be gone in far too short a time to get the coach stopped.

Please do not attempt to discount our warnings of serious danger to one of our brethren with examples of successful ignorance.

happy coaching!
buswarrior