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  #11  
Old 9th March 2014, 17:12
G-CPTN G-CPTN is offline  
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Looks like the governor/unloader valve is remote mounted (see the black eighth-inch signal pipe at 0:57:- http://www.youtube.com/watch?v=rRaNwv7OlZU - though that could be a sensing pipe).
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  #12  
Old 9th March 2014, 17:22
G-CPTN G-CPTN is offline  
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Mounted in unit with the engine-gearbox assembly, but having an independent lubrication system from either of the other units, is a 48° bevel box. This incorporates helical reduction gearing, and it is this gearing which is changed to suit the requirements of any particular operator in respect of a specific final-drive ratio.
It is much cheaper to offer an alternative set of helical gears for the bevel box than to provide a variety of sets of crown wheels and pinions. In the Leyland final-drive arrangement there is one standard rear-axle ratio of 3.083 to 1, but a choice of final-drive ratios of 6.074, 5.334, 4.702 and 4.15 to 1.
From (and more at):- http://archive.commercialmotor.com/a...wn-to-business

Though that is 1958!
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  #13  
Old 9th March 2014, 17:26
VBV_18Y VBV_18Y is offline  
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Ah yes, cheers for that, right what it does is, when i fire her up the air system makes a knocking sound, it goes pssshhh knock.


http://www.youtube.com/watch?v=plGoxQG9KvU you can hear it in this.
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  #14  
Old 9th March 2014, 17:30
VBV_18Y VBV_18Y is offline  
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Gonna have a good read at that.

As you can tell im a complete novice at this game but you know old folks can't live forever, us young'uns have to carry the flame on.


Well i have an idea, i'll try repairing it first, if not, i'll buy one.
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  #15  
Old 9th March 2014, 18:14
G-CPTN G-CPTN is offline  
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Originally Posted by VBV_18Y View Post
Ah yes, cheers for that, right what it does is, when i fire her up the air system makes a knocking sound, it goes pssshhh knock.


http://www.youtube.com/watch?v=plGoxQG9KvU you can hear it in this.
I cannot identify the problem from that (other than the air pressure isn't building).

Check for where any air is leaking around the engine with the engine idling (the pressure should still build). If there is no air escaping then you could have a stuck non-return valve somewhere.

Do you have access to anybody with 'experience' who can look at your vehicle? I suspect that there are other buses parked adjacent (from the earlier video) - or have they towed it and dumped it in your driveway?

In the earlier video everything seemed to be working just fine - so what has happened in the meantime?

Seals and diaphragms do perish (and stick) - you just have to find out where the trouble lies before spending money on replacement parts that might not be necessary.
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  #16  
Old 9th March 2014, 22:15
VBV_18Y VBV_18Y is offline  
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Me and some mates have 7 Atlanteans and various other buses, i'll ask a mate to have a look. but like you said something could be stuck, the pssh knock sound has always been done since day one.
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  #17  
Old 9th March 2014, 23:37
G-CPTN G-CPTN is offline  
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I couldn't detect anything unusual.

When a compressor is working it does tend to 'knock' as it compresses the air (it's hard work - like an engine in reverse). The air should pass directly to the first 'receiver' (usually a condensing tank) before moving on to the air reservoirs.

The gauges will be on the reservoirs - not the condensing tank. The signal for the unloader/governor valve will probably be taken from the condensing tank (via a small diameter plastic pipe) and there will be non-return valves between the condensing tank and the air reservoirs.

Usually (in Britain) the unloader/governor valve is not attached directly to the compressor but sends its signal to unload the compressor via a small diameter plastic pipe.

As I've stated, disconnecting the unloader/governor valve pipes should allow the compressor to 'charge'. It could be that the unloader piston in the compressor is stuck in the 'open' position (though this would not be the case if the vehicle was left without air in the system - only if it had been left fully-charged with no leaks).

In normal operation it requires air from the unloader/governor valve (from a fully-charged system) to operate the unloader in the compressor. This only happens when the pressure in the unloader/governor valve pushes the valve against the spring. An internal leak within the unloader/governor valve (it has pistons and seals) might feed air directly to the compressor, but disconnecting the unloader/governor valve piping to the compressor should tell you if that is the case (and should start the compressor working again).

It could be that your friends are talking about the unloader mechanism in the compressor rather than the (usually) separate unloader (governor) valve. In which case the problem might lie within the compressor cylinder head (the piston which depresses the inlet valve to stop it compressing air). If that is the case then you are looking at repairing the compressor (new seals in the unloader piston).
You should be able to dismantle the unloader piston without removing the compressor cylinder head (you will need seals for the piston and maybe new spring(s) if broken (unlikely I'd say), but if the inlet valves are not seating then it's a (compressor) head-off job - no need to remove the compressor - that would be a major major job as no doubt the fuel injection pump is driven from the back of the compressor?

Do the diagnostics first, as you need to know where the problem lies before you start pulling things apart!

Watch the videos in:- http://www.truckandbusforum.com/showthread.php?t=4674
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