Well after getting the E-P valve reconditioned and re-fitted we still had no second gear so taking Ian and Mark P's advice my man on site finally got to grips with the underneath of the gearbox to see if he could hear the air bubbling when the gear was selected only to notice that something had hit the second gear pipe and bent it over, when straightened all gears were available!! Only problem now is the Control box where comparing it's contents to the one on RM 1585 a non refurb, we find lots of boxes in the control box on the RML that are not on the RM including a push button unit, a Bosch unit that says ALT-R on it, a Hella Unit and an Inteltech unit, but none of the bits that we were expected to find. If anyone has similar set up (Cummins engine SCG gearbox) ex Centre west bus and can suggest what these boxes do and/or why they might affect the batteries getting a charge please let me know!! Also thanks for the time yesterday Mark P, much appreciated.

My bus number (if any): RTl 960 RMC 1485

Hi Brian
Glad the fault was identified and glad for you that it wasn't the gear piston seals - who'd have thought a bent pipe eh! although it shouldn't have been dropping the air to make the warning light come on. From your description it is the bosch unit that is likely to be the regulator - suggest that you try David Collin (RML2276) who posts on the Network forum and seems to have a good background in LT vehicle electrics post refurb

Regards

Mark

My bus number (if any): RM1414 sort of

The gearbox problem is not completely cured Mark, the warning light might be trying to tell us something! It drives fine for 5 minutes or so then starts losing 2nd and 3rd gears and the warning light comes on, Philippe says its akin to a clutch slipping, 1st and top are fine. When air is exhausted from the tank, the light goes out and it works fine again for 5 minutes or so, (so doubt problem is in the gearbox), can too much air be a problem, can the air pressure be regulated?? Any suggestions welcomed!!

TIA

Brian

My bus number (if any): RTl 960 RMC 1485

Hi Brian
(If you tried to call this morning, i was out multi drop driving and had no cab kit for phone)

If in 2nd and third the light comes on and it feel like slipping drive then the air supply has dropped too low, the pressure to the ep valve is regulated to between 60 to 81 psi depanding on what valve and what it is set to, the warning light sender is between the ep valve and the regulator valve and can be found on the crossmember (usually centre nearside or plain centre) that goes across the front of the gearbox and can generally be viewed through the lower saloon floor trap (gearbox one and look forward).
It should affect all gears not just one or two unless the fault is actually the piping or unions on 2 and 3 between the ep and the gearbox or it is actaully the seals on the pistons for 2 and 3 starting to pass air. The air leak wherever it is is obviuosly severe enough for the compressor not to keep up with it unless of course the is a fault with either the air blow off valve (not charging the air tank/ cut in) or regulator valve.
Phillipe needs to test each gear in turn with the engine off but ignition on and air up and listen for air leaks/bubbling fluid in g/box
At least the ep valve can be ruled out as you have had that checked in the UK.
If you need to chat then tomorrow daytime will be difficult due to proper work ;( but you can give me a call from 1900 ish onwards on the landline (should end 1052 not 2122) that our mutual friend in Warrington has given you

HTH

Mark

My bus number (if any): RM1414 sort of

Hi Mark

Yes I did try you today, but we might have cured the problem, I'm glad too much air was ruled out!! When Philippe mentioned that he got the gears back after he exhausted the air from the tank and it was OK for 5 minutes or when he changed down after that time that got me thinking along the lines of too little air too, so I asked him if he was getting anything apart from air out of the tank (he was using the drain plug to let out the air and he said he was getting a lot of water and crap out, the bus has been standing around for almost 2 years which probably goes a long way to explaining the problem if water was in the air going to the gearbox wouldn't it?
I haven't heard from him today so I am assuming that by letting out the water he has improved the air supply to the gearbox and its OK now, either that or he is stuck in St Tropez which is where he was heading, there are worst places!! Thanks very much for the help, much appreciated.

My bus number (if any): RTl 960 RMC 1485

Bus arrived safely at St Tropez. The airtank was cleaned out by repeated exhausting "it was like mayonnaise coming out" and that cured the loss of gears problem. My brother tells me draining the airtank was a 100% job on every rota inspection at LT garages on RMs, not sure if its on any maintenance chart currently sold though.

Thanks to all for their input and interest.

My bus number (if any): RTl 960 RMC 1485

Correction to the above. Draining air and dirt/water out through the cut-off valve did cure the problem but only temporarily. The bus got to its destination by using top gear as much as possible.

Its a mystery as everything Mark P has said above is correct and the problem should be low pressure causing the low pressure warning light to come on and the loss of gears. However, when air is exhausted from the tank and the bus restarted, the warning light goes out and all gears works OK for 5 minutes or so. can anyone explain how can reducing the air in the tank be a knocking out the warning light and curing the loss of gears albeit temporarily? Anyone got a centre west bus with "a drier" on the air pipes?

My bus number (if any): RTl 960 RMC 1485

It might be worth removing the reducer and pressure release values, taking them to a workbench and dismantling them carefully to clean out any "mayo" from the workings. I suggest photographing everything as you dismantle it so that you've got a record of how to re-assemble it and watch out for circlips and spings pinging across the workbench.

RML 2644 suffers from mayo buildup quite badly and I regularly have to clean the two valves. My suspicion is that the seals on the compressor are worn which lets too much oil into the air-stream, when combined with the water vapour in the air this results in the mayo that clogs the valves.

My bus number (if any): 2644

I prefer mayo to compressor snot, the term used at Nene Valley Railway for the residue drained from their brake air receivers.

My bus number (if any): RM238, RM471 and RM2213

Right.
Find a suitable fitting, length of pipe and gauge and check the air pressure in the tank as per the manual.

Now, assuming all that is ok....remove the rubber pipe which feeds air to the gearbox. Fit a length of pipe long enough to reach out from under the bus. Fit T piece to the end. To one side of the T fit a pressure gauge up to about 150psi. To the other side of the T fit a tap or bellows type air blow gun. Sart engine, allow pressure to build up to operating pressure. Unloader will cut in, pressure will drop slightly then build up again. (remember, there is No air getting to the gearbox now, its going down your pipe). Open tap briefly to simulate a gearchange. Pssssst! You get a quick blast. Pressure drops momentarily then quickly recovers. Do it again, and again, faster, simulating rapid gearchanges. Pressure should stay pretty constant but will probably start to tail off in your case. Now open the tap fully. You should get a blast of air, the gauge will drop to nothing, then a constant supply of air running at the pressure the compressor can supply. I suspect in your case you will get an initial blast then a tiny trickle of air.
I suspect your reducer valve is sticking or knackered. This is characterised by the initial maintaining of pressure which eventually fades away. (So the unloader still operates correctly, as the pressure in the tank is right. Its what is coming OUT of the tank which is too low to operate the gears).

My bus number (if any): RM531

Thanks Steve, I think we might be able to manage to clean the valves out, not so easy to rig up test units in the middle of St Tropez which is where the bus is now. But its good to know what I think we all knew that too high air pressure cannot cause gear failure, but hard to get through to somebody who thinks he has cured the failure by draining off air!! Your diagnosis of low pressure in the pipes but high in the tank makes perfect sense.

Thanks again to you and Mark for helping with this "diagnosis" from afar.

Brian

My bus number (if any): RTl 960 RMC 1485