dar1976:
For me the needles kept bouncing up and down on the air tank gauges. One would show full and the other would show empty. Then they would swap over.Gears were getting stiff. Clutch unresponsive. Brakes intermittent. Suspension raising and lowering on level ground.
Rang the TM who suggested bleeding the tanks.
cheers dar
jenx
Just looked on my Renault , there are no rings ( its nearly 3 years old so you can see how often I drain the tanks) 
The drain plug looks like this :-
Denis F:
Just looked on my Renault , there are no rings ( its nearly 3 years old so you can see how often I drain the tanks)
so that one would you need to unscrew and release ?
jx
They probably didn’t expect a Reno to last 3 yrs and need the tanks bleeding… 
The tank drain is generally like a little peg that is “sprung” into it’s cetral position. So a ring can be fitted to the end and then a bit of wire attached to the ring for remote control (saves getting the grey sludge up your arm). It’s just a matter of “disturbing” the little peg and that will release the air.
Two reasons for doing it: Maximises the capacity in the tank for air rather than sludge. Avoids freezing.
But, in these days of air dryers, the problems have all but gone.
Hope this helps, Pete
Jennie:
Denis F:
Just looked on my Renault , there are no rings ( its nearly 3 years old so you can see how often I drain the tanks)so that one would you need to unscrew and release ?
jx
Noooooooo,just get a long stick and poke it gently,the peg sticking out.Sometimes they wont sit back right so fiddle with the bugger to seal it again.
Give one a poke Jen next time your bored but do it at base after your shift in case something silly happens.
ShropsBri:
Give one a poke Jen next time your bored but do it at base after your shift in case something silly happens.
And when, sorry if, you get covered in grey sludge don’t forget to post the pictures on here. 
Coffeeholic:
ShropsBri:
Give one a poke Jen next time your bored but do it at base after your shift in case something silly happens.And when, sorry if, you get covered in grey sludge don’t forget to post the pictures on here.
that`ll be a given then,
somat always goes wrong when i poke somat i shouldnt 
jx
Jennie:
Coffeeholic:
ShropsBri:
Give one a poke Jen next time your bored but do it at base after your shift in case something silly happens.And when, sorry if, you get covered in grey sludge don’t forget to post the pictures on here.
that`ll be a given then,
somat always goes wrong when i poke somat i shouldntjx
Oooooer 
dar1976:
Jennie:
Coffeeholic:
ShropsBri:
Give one a poke Jen next time your bored but do it at base after your shift in case something silly happens.And when, sorry if, you get covered in grey sludge don’t forget to post the pictures on here.
that`ll be a given then,
somat always goes wrong when i poke somat i shouldntjx
Oooooer
behave now dean
It’s ok. I’m used to getting the blame for lowering the tone
Last time a drained my tanks was last winter and it was 0300 and minus 22 degrees 
I pulled the cable attached to the ring on the tank and as soon as the air/water/sludge shot out it froze instantly. It had no effect as everything was working okay anyway - I have no idea why I did it but it made me feel better if nothing else
I believe the grey sludge is the oil from the air compressor unit mixing with the water. If your vehicle is producing a lot of this then the compressor will need replacing at some point because it lubrication system is leaking.
A lot of this stuff will be collected by the air candescent filter. It is normally near the front near side wheel, has a blow off valve under it which basically blows out the crap for you automatically. If the blow off on the underside is very caked in oil, then again the compressor is sending lots of oil through because it’s wearing out. The filter should in my opinion be replaced every 6 months to prevent the sludge from spreading to the tanks, valves and other equipment. This can save problems developing in the air assisted clutch and range devices especially on DAF’s.
I drain my tanks now and then but don’t often see any muck exit the drain valve. Modern trucks are so much better.
If you operate the drain valve and it continues to leak once released. Don’t worry, just give it a wiggle or a tap. They don’t seal very well if it’s not been disturbed for some time.
Tockwith Training, providing quality driver instruction since 1971
The best way is to do it once a few months, when the weather is really wet, You can always see and hear on the when the truck lets the air out and the meters arent on the top of the scale. The tanks are covered inside with prafine so they wont get rosted anyhow.