Good day to all, our bus, RML2505, Iveco engine, starts and runs well given her idle life style at this time, but, today we have noticed on start up the red gearbox warning light stays on longer than normal, by revving the engine the “fault” clears and the light goes out and we can select gears, but once we stop and the engine returns to idle, the light comes on again, by repeating the revving we can clear it, am I looking at a pressure problem or can someone enlighten us as to the probable remedy, something simple or “call an engineer!”
We only engaged reverse today moving back about six feet and then first to bring her back to her usual parking spot.

My bus number (if any): RML 2505

It is the air from the tank/compressor.

It could be a leak in the pipework, or the tank, or more serious, the compressor not working as well as before, and not compressing as much air on idle as before. If that persists or gets worse you will need your compressor refurbished.

Id say first task would be to look underneath with it running for leaks.

My bus number (if any): RML2323

Apart from being dangerous with so many things whizzing round which can kill you, it is almost pointless getting underneath the bus when the engine is running in order to look for an air leak - you won't hear anything because of the noise. Look for the leak immediately after stopping the engine.

In my experience the most usual cause is the outlet pipe from the compressor is loose. where people have over-tightened it over the years, the olive has worn and no longer forms an air tight seal. Cut the end off the pipe and fit a new olive, available from plumbers merchants.

Chaps,

Having read the above and being concerned that occasionally, when engaging first or reverse after start up it needs a boot full of revs to start moving, I shoved my head under after I had stopped the engine. I could hear the all too familiar sound of compressed air escaping. At best as I can tell is coming from the gubbins on the front of the air tank. Is this normal decompression at the end of a days work or a leak that I should be worried about?

Thanks.

My bus number (if any): RM1013

If you can plainly hear an air leak it is excessive. To find it, you can either use soapy water, which I don't find very effective, or a leak detector spray which can be obtained from a plumbers' merchant (Plumbase etc).

Trying to pull away with insufficient air and revving the engine to compensate will damage the brake bands in the gearbox.

Hello Hugo

If by gubbins you mean one of these or similar.........



............it is the reducer valve, that is the valve that limits the pressure that gets through to the gearbox. This is not the same as the cut off valve which controls (by venting to atmosphere) the compressed air into the tank. That valve is in the line between the compressor and the tank.

If it is leaking out of a small vent hole in the body it will almost certainly be the spring under the base plate (two 6mm bolts) which will have rusted away due to moisture. The spring pushes a diaphragm to control the air pressure, when it exceeds the setting the diaphragm overcomes the spring pressure and allows air to vent. With the spring rusted away the air continuously flows out of the vent hole. One thing that should be regularly done is emptying of the water in the air tank by pulling the ring at the base of the tank when the air pressure is up. This may well prevent corrosion. I did a quick get you home fix by securing a jubilee clip over the hole to reduce the air escaping. I wouldn't advise blocking the vent completely or using it as a long term fix.

The valves are in very short supply and the springs or repair kits are not available. I did have a quote to manufacture them but with all the other parts that could go wrong decided to replace the whole valve with a modern unit:



My original write of about the change can be found in the RMOOA magazine three or four issues ago I think or on this site at

http://pub44.bravenet.com/forum/static/show.php?usernum=3715842662&frmid=32&msgid=1175531&cmd=show

In place it looks like this



That said, no one else has ever claimed to have installed one of these so perhaps the originals are more available than I discovered or our suppliers let on.


David Colin

My bus number (if any): RML 2276 M1001 T806