Air Tanks and Drains

[PacificaDen]

Thanks for starting this thread....Can't find my tank, nor in the literature from "Freightliner" who made the chassis for my unit.

What I am really wondering is, when the engine is idling, is the air POP AND HISS coming off the tank and is this the auto drains folks are talking about above??? Would tracing this sound be a good way to find a valve for draining the fluids manually????

[Skip426]

Originally Posted by PacificaDen

Thanks for starting this thread....Can't find my tank, nor in the literature from "Freightliner" who made the chassis for my unit.

What I am really wondering is, when the engine is idling, is the air POP AND HISS coming off the tank and is this the auto drains folks are talking about above??? Would tracing this sound be a good way to find a valve for draining the fluids manually????

There are a couple of possibilities for the sounds , the air system dryer has an ejector that cycles too.

The air tanks on my 99 XC chassis , are between the frame rails just behind the front axle , the lanyards for my manual drains are run through holes in the passenger side frame rail and are visible when looking over the right front tire .
The air system dryer is mounted inside the drivers side frame rail , behind the differential next too the transmission.

[twinboat]

Originally Posted by TenRacing

The drains in reference are on the air tanks and would be moisture drains so I would say they have some type of sensor for said moisture.



Mine has one of these auto drains leaking around the seam of the body.



Will likely replace with manual tether drains might try to disassemble and re seal first

Here is the description of operation of the Bendix DV2 auto drain valve.

[TenRacing]

Originally Posted by PacificaDen

Thanks for starting this thread....Can't find my tank, nor in the literature from "Freightliner" who made the chassis for my unit.

What I am really wondering is, when the engine is idling, is the air POP AND HISS coming off the tank, and is this the auto drains folks are talking about above??? Would tracing this sound be a good way to find a valve for draining the fluids manually????

that is an overpressure release valve you hear popping and hissing. done by the dryer. the moisture drains are on the air tanks and just for removing any moisture from the system that may build up over time and or happens to get by the dryer.

[twinboat]

Originally Posted by TenRacing

that is an overpressure release valve you hear popping and hissing. done by the dryer. the moisture drains are on the air tanks and just for removing any moisture from the system that may build up over time and or happens to get by the dryer.

It's not an overpresdure release valve, it's a purge valve on the bottom of the air dryer that opens from a signal sent from the compressor governor.

It's closed while the compressor is filling the tanks and when the tank reaches the governor set point, the governor sends a signal to both the compressor and air dryer to stop pumping and purge ( empty ) any moisture filled air that the dryer collected.

Use some air and the cycle starts again.

[TenRacing]

So I pulled the leaky drain off of the one tank, dry inside replaced an o-ring that seals the body halves. in the process I found that there are push valves on the side that drain the tank. One of the 3 had about a pint to a quart of water in it!

The one tank looks to have a divider, so it has 2 of these things on it, the one that had water in it the drain was nasty corroded and had muddy goo in it, I got it cleaned up good and re-installed. the last one I have it off now and was dry inside so just need to get another o-ring. and re install.

[TenRacing]

Originally Posted by tomgrigsby

Following. I need to find mine too, same year 3851 Spartan.

above the front axle. mine had 'spitters' auto drains.

[TenRacing]

UPDATE, I have now rebuilt and re-installed the compressor, the compressor had a bad intake reed valve.

Put manual drains with tethers on 2 of the 3 drain points on the tanks. 3rd one I need to figure out longer tether.

[96 Wideglide]

Originally Posted by TenRacing

The one tank looks to have a divider, so it has 2 of these things on it, the one that had water in it the drain was nasty corroded and had muddy goo in it, I got it cleaned up good and re-installed.

Yeah, I'll take a pass on the 'auto drains' !

[TenRacing]

Originally Posted by Tommyk

I have the same automatic drains but don’t know how to verify they are working. I’m changing filters today on the air system. Any help would be appreciated!

mine have/had button on the side to manually bleed them off, that is how I found that one of mine was not working.

I used the old soapy water spray bottle trick to find one of them was leaking around the body. removed replaced o-ring inside and got it working, but replaced two of them with manual tethered drains.

[FloridaSon]

First time I pulled my tank lanyard valves, two didn’t budge and had to be replaced. This was after dealer assured me the auto drain and air dryer eliminated the need. The tank with a short divider is called the wet tank by freightliner. I never thought the angle on those lanyards were correct but guess they are.

[capt fast]

'98 3856 DS with the IFS. the air reservoirs are located between the frame rails above and aft the front suspension goodies. the tanks are equipped with automatic drain valves and there is a manual actuator on the valves you can pull with the help of a pin or a paperclip looped thru the small hole in the actuator pin. I keep my air drier serviced nicely and have never got any water out of the drains when I've manually energized the valves during pre trip checks. there has never been any lanyards on them.

[capt fast]

I would recommend servicing the air drier unit on your coach because it seems that it isn't doing much drying of air for your systems.