Clayton Dewandre Air Operated Clutch

Hi, we have a problem with the clutch in our '54 AEC Reliance bus, it will only hold air while you have clutch held down. When you release it air escapes out the transmission breather. Was told by previous owner it had a "sticky valve" but we have gone through and we have cleaned all the valves up - what are we missing?!

Murtle
HowDoo

for a start I no nutn about AEC buses or air clutches
I can't even spell AEC
LOL
But lookn @ the problem U could sumise the following
the bus is over 50 years old
U could imagine th@ for 99.99% of the time the clutch is in the engaged position
therefor the Piston or shaft in the clutch air cylinder is in the one postion most of the time, it could have worn a flat spot or groove in this position, from normal use n vibration, th@'d cause air to bypass piston
so I'd B inclined to get it machined n fit over size piston n rings or get it sleeved in stainless steel just like they do with hyd brake wheel cylinders

Ifn U get my drift

ButEyeDoSt&2BCorrected

Have U got any pix of the culprit in Q:?



Cya

[ch9787]

Thanks very much for your quick reply, thats what makes sense to us too! But the manual that came with it says if it won't hold pressure to look at the check valve, we have done that too! Will post some pikkies tomorrow.

Murtle,given the age of the old girl,what Swishy has pionted out makes a lot of sense.On another tack,when a treadle valve or a relay valve starts to fail,the bit that seals against the rubber has usually bitten into the rubber to the piont that that it wont seal any more.You might find that,being air assisted,the reason it doesn`t leak when it`s working is that the piston is off the damaged seat and the air is diverted to the cylinder.I`ve driven some gems that won`t build up air pressure because the Treadle valve is leaking that badly,the trick is to put your foot on the treadle valve while you rev the sh*t out of it,and the air will build up,as long as there isn`t to many other leaks in the system.The check valve only stops the airt going one way,have a look and see if you can find the valve that actuates the cylinder.
If it`s all cactus you may be able to adapt sopmething else,the clever chinamen have got copies of the european and japanese clutch servo`s,I reckon you might be pushing shite up hill with a very pionty stick if they had a copy of the Clayton one.

You don't say where you are but if around newcastle ask the expert in these old jiggers who is Joe Fogarty, pm trucknbus for contact.
Is it a pre engage gear box or manual?

Hi Bigcam and Mammoth, thanks for your replies. We were told today to check the transmission piston. We did and have found the rubber seal is rock hard! Are waiting on a seal that hopefully will do the job. Oh by the way we are in Waipukurau, New Zealand!

From my experiance with AEC buses, it's usually the air pistion seal, under a cover on the left/top side of the box. An easy job to change. It sounds like it is a Wilson preselect transmisssion to me.
Its not an air clutch it's a gear change pedal. It finalises the preselected gear change when required.