Drain the tanks.
There are…
Small valves underneath the air tanks themselves. These are bleed valves. Just pull the wire they are attached to and the air should drain out of the tank along with any moisture. If there isn’t a wire then get a stick or something and push the valve.
I thought Mercs had air dryers with replaceable filters (or was i imagining), and seem to remember looking for drain taps on the square Axor i used to use regularly, no manual drain taps fitted that i could find.
ChrisEnglish90:
Morning guys.Recently started a new job and just been allocated a truck to use daily. Having turned it on it came up saying moisture in air tank res. Just wondering how I’d empty this? I spoke to another lad who said this truck has had this issue fixed but it’s still showing up? For piece of mind I’d like to ensure it is drained. If it’s not something easy to do then I’ll report it to be fixed but I’ll report it anyway!
Any help appreciated.
If there is moisture in the reservoirs, then it suggests that the air drier isn’t doing what it’s there to do. I haven’t had fluid in an air tank for many years.
If it’s a reason ably new truck I think it’s likely to be a sensor fault. Best checked though as long term t will cause all sorts of other issues with the air system.Sent from my iPhone using Tapatalk
Juddian:
I thought Mercs had air dryers with replaceable filters (or was i imagining), and seem to remember looking for drain taps on the square Axor i used to use regularly, no manual drain taps fitted that i could find.
Classic case of over complicating a simple system, moisture in the air tanks pull a valve moisture gone what could be simpler, oh wait a minute lets put an air dryer into the system then when it breaks only a dealer can rectify it, kerching thank you very much for adding to Mercedes’ profits.
Mazzer2:
Juddian:
I thought Mercs had air dryers with replaceable filters (or was i imagining), and seem to remember looking for drain taps on the square Axor i used to use regularly, no manual drain taps fitted that i could find.Classic case of over complicating a simple system, moisture in the air tanks pull a valve moisture gone what could be simpler, oh wait a minute lets put an air dryer into the system then when it breaks only a dealer can rectify it, kerching thank you very much for adding to Mercedes’ profits.
All modern trucks have candescent filled filters(air dryer) they take a large amount of the moisture out of the incoming air, the moisture occurs with the air in the tanks, the filters should be changed every 6mths, but to save pennies lots now change them every 12 or even 24mths, or they don’t get changed till the system goes wrong. Contract maintenance classic example.
biggriffin:
Mazzer2:
Juddian:
I thought Mercs had air dryers with replaceable filters (or was i imagining), and seem to remember looking for drain taps on the square Axor i used to use regularly, no manual drain taps fitted that i could find.Classic case of over complicating a simple system, moisture in the air tanks pull a valve moisture gone what could be simpler, oh wait a minute lets put an air dryer into the system then when it breaks only a dealer can rectify it, kerching thank you very much for adding to Mercedes’ profits.
All modern trucks have candescent filled filters(air dryer) they take a large amount of the moisture out of the incoming air, the moisture occurs with the air in the tanks, the filters should be changed every 6mths, but to save pennies lots now change them every 12 or even 24mths, or they don’t get changed till the system goes wrong. Contract maintenance classic example.
Especially useful to leave the filters in over a really cold winter so the dryer filter freezes solid.
You couldn’t trust modern wheel attendants to drain the tanks, some of them never check the engine oil or look at the tyres, plant pots, imagine trying to explain moisture in the air system to 'em if they can’t work out what lack of oil might mean 
Like all trucks mercs have several air tanks, only one tank has the mosture sensor fitted, the others have drain bungs (no tap but plain blanking bungs) to drain you have to loosen the bungs a couple of turns to expose a little drain hole in the bung itself and you cannot screw them back in until all the air is out otherwise you shag the sealing 0-ring, if you undo the bung to far you go deaf!
Basically its a workshop job.
ERFs don’t have tank drains valves the air dryer blows snot out on to the floor 
Gone are the days when my old D800 had to be drained…could have filled a bucket…ha ha
Loved that black sludge! And getting a bollocking for wasting alcohol in the dosing bottle
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