I have got my gearbox warning light staying on far too long. The search for an air leak didn't take to long....

This component is leaking an awful lot! There is a little hole on the underside which air is just pouring out.



Is this still a part which is available?

I am assuming (you know what they say about assumption!) that this is the source of the problem. The gearbox warning light does eventually go out.

What exactly does it do?

Any help would be much appreciated.

Regards,
Tom

My bus number (if any): RML2344

Evening Tom.

think it is the throttle dip valve. It operates when changing gear dropping the throttle briefly to reduce wear on the gearbox Never looked at mine so don't know much about it. The item I found leaking was the reducer valve on the tank. I found a modern replacement for that bit. Not heard of anyone having a problem with the part you have before. It would be useful to find details. I will make some enquiries. Hopefully someone on here will know.

David

My bus number (if any): 2276 1001 806

Yes, it's the throttle dip valve. I took mine off and replaced it with a piece of solid rod. You can get a replacement valve from ADL. I've got the part number somewhere.

Inside it are a couple of rubber seals which have probably worn out.

My bus number (if any): GS67 RML2532

Good afternoon,

If you do have the part number that would be much appreciated. It would good just to reassure myself that I am ordering the right part.

Also, ADL, just checking you mean the New Zealand part firm -http://www.adl.co.nz/

I thank you for your time.

Kind regards,
Tom.

My bus number (if any): RML2344

Hi Tom - I think Roy is probably refering to Alexander Dennis Ltd 01483 571271 in Guildford ?

My bus number (if any): RML2747

ADL=Alexander Dennis Ltd.

sorry I can't find the part number for the throttle dip valve. If it's any help to anyone, the throttle cable is 236405-6.

My bus number (if any): GS67 RML2532

My (Cummins) RML has a Parker 40400y valve. Have searched online and had a couple of prices from my suppliers. Best deal I have found is £142 exc. delivery and VAT and they are on as much as a four week lead time. Partline do not do them or Airlec for that matter. Airlec thought they were obsolete.
Lots of American sites show them but appear to be equally as expensive.

One company with them in stock is

http://www.plccenter.co.uk/Buy/PARKER/40400Y @ £266 each!

Could do with stripping one to see if they are repairable.

Are they actually needed given the more careful driving of the owner/driver? If you only drive in manual then they could be removed if you change gear correctly :)

If anyone else knows a stockist please let me know.

David Colin

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

Have found another supplier at similar cost and lead time. They tell me Parker have made or are making many parts obsolete and the price then increases. They have agreed to look at the spec to see if a new alternative is available. I will get them to look at the other valves and switches we use in the air system

David

Had a call from them. It is not a valve apparently but a cylinder. Having looked at mine (which differs to yours in the way it is installed) it operates by having the air switched off elsewhere (using an ep valve) which shortens the throttle linkage length to drop the revs. This is how some retrofitted road speed limiters work by the way. They may have an alternative but it may need modification to mount it. At half the price and easier to get it may be worthwhile looking into this further

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

Which is why I replaced mine with bit of threaded rod!

My bus number (if any): GS67 RML2532

You do not need to replace the Dip Valve.
What I did with one of my RML's was
Remove the air feed and seal it, then fit a spacer over the rod on the dip valve which then locks the valve, I used 2 x nyloc nuts as spacers and that's it

Regards

Rob

Tom the idea of it is to momentarily dip the revs between gear changes in auto - mine also has the threaded rod it makes the changes in auto a bit more jerky but if you always drive in semi it makes no difference as you would take your foot off between changes anyway ? I changed mine as the dip had a habit of causing loss of revs when reversing more than a few yards and having to restart everything to get your accelerator back !

My bus number (if any): RML2747

ALD - that makes more sence!

The problem is that its not just me that drives it and I like the auto option when I driving around a city for hours on end.

Okay, I have some options and will see what I can come up with.

My bus number (if any): RML2344

This is a bit like the product sales promotions one sees: " when it's gone, it's gone". Which in this instance means insufficient demand for product? then product no longer available.

I only have regular driving experience of one bus with the cylinder removed and to be honest it is not a pleasurable experience.Auto changes are very jerky and unless a manual change is absolutely spot-on then these can be too. The gearbox band settings and quick release valves are all OK and not worth the expense and time of repeated trimming. The bus was better before the cylinder was deactivated.

The main advantage I can see of removing it is that on some buses it makes rollerbrake testing the vehicle a lot easier.