Help! Parked the bus up a couple of weeks ago up here in Scotland. Went to use it today and..... no gears. Tried filling inverter thingy with oil and no difference. Red light in cab stays illuminated. Any ideas for a man with limited RM knowledge?
Thanks
Charlie

My bus number (if any): RML2232, RML2358

The fact that the red light is illuminated permanantly tells you that there is a problem with the gearbox air pressure. You do not say if your bus is "origional condition" or "refurbished".
1. Possible causes- failed compressor, slipping compressor or broken belts or sticking unloader valve.
2. Can you hear air leaking under the bus? Lift up the gearbox trap in the saloon floor then start the engine and listen. Be VERY CAREFULL of rotating propshafts. Check also the compessor belts ( On the back of the gearbox, on the rear propshaft before sarting the engine)
3. With the engine off after running for a few mins, can you hear air leaks? This can indicate a sticking unloader valve (this is the lump bolted onto the end of the cylindrical air tank underneath the bus roughly under the second nearside window- you can easily see it if you look underneath). Another cause is the gearbox air pressure reducer valve sticking/failed. This is on the chassis crossember in front of the gearbox. Dont attempt to see it without an access pit with the engine running due to rotating front propshaft which will permanantly rearrange you. Getting under with the engine stopped, after running for 5 minutes or so should reveal any hisses. It may just be a loose conection! You should not hear any air hissing beneath a routemaster at all, other than an occasional pssssst from the unloader valve as it operates, depending on the type fitted. Any air noise at all is likely to point to your problem.

My bus number (if any): RM531

If you go under the bus mix up some washing up liquid in water and brush it onto any joints you suspect of leakage. This will show up even the smallest pinhole leak.

The gearbox air supply can also get gunked up with "Mayo", which gets formed by water in the air mixing with the compressor lubricating oil. This gunks up the pressure valves and sensors.

If you've not got any obvious air leaks and the compressor belt isn't slipping then this is the next most likely candidate. Remove the valves from the bus, take them inside to a clean well lit workbench, dismantle carefully noting the assembly order, clean out any "mayo", reassemble and replace using fresh PTFE tape on the joins. It takes a while, but it's not difficult.

My bus number (if any): RML2644