Hi Everyone,

Have a slight problem with RML2719, she will not go through a brake test, even after stripping them down and rebuilding them. School of thought seems to be that the accumulators need recharging??? Is this possible to do with them in place, or do they have to be removed and sent away?

Help and advice please

regards

Chris

My bus number (if any): RML2719

Good morning Mr Arnold
Accumulators should not really affect brake performance as they are a back up in case of engine failure, however, they can be charged on the bus.
Everything you need to know is on the very informative RM 1872 South Devon Railway site. Just Google RM1872 and follow the link in the 10th August 2005 write up.

My bus number (if any): RTL 960, RMC 1458 RM 1585, (M 961, M 271 - both sold) and several RTs

If it`s a case of the accumulators need recharging, has there been no prior warning of this such as flag drop?

It could be a number of things. What was the failure for? Imbalance, poor performance, flag dropping.. Did you push the pedal to the floor? The last 10mm of pedal gives double the line pressure so the brakes should lock out all round. What type of accumulators have you got?

Let us know the brake print out figures.

My bus number (if any): RML2532

Thank you for your input, as always it is invaluable.

I have spoken to the testing station and they are saying that the last bit of the pedal is soft and they are saying it is a combination of imbalance and poor performance

27% imbalance Right to Left

Service Brake is 25% and needs to be 45%

System A is reading 11% must be 22%

System B is reading 13% must be 22%

If anyone can offer me a solution, i would be eternally grateful

Thanks as always

Chris

My bus number (if any): RML2719

So many possibilities, did MOT station mention shoe thickness Have you checked the shoes through the witness hole, is there a big gap between shoes and drums?
Have you tried bleeding the brakes? When was fluid last changed? Have you checked for air leaks? Are the RP auto adjusters free and not seized? (can you turn the adjuster key?)

My bus number (if any): RTL 960, RMC 1458 RM 1585, (M 961, M 271 - both sold) and several RTs

Are the rollers on the brake shoes seized? What are the brake line pressures? Sounds like it needs a good looking at by someone with the right test equipment to sort this. It is unlikely to be just the accumulators. Are the Plessey pump belts tight?

The figures you give are remarkably low. After adjustment you should get 65% on the foot brake and 38% on the handbrake with all wheels locking.

Where is the bus based?

My bus number (if any): RML2532

Certainly agree. Those are some pretty pathetic brake efficiency figures. Fred Flintstone could probably stop quicker. I am surprised you didn't get an immediate prohibition. This needs a thorough sort-out.

There's a lot that could be wrong with this bus, has it been laid up for a long time? When was the last time anyone serviced it? It sounds like some of those I see abroad!

If you want it done, I'm sure either myself or roy could do it, depending where the bus is at the moment. We're both based in Kent. It may cost a lot, depending on what is found to be wrong.

My bus number (if any): RML2532

Good Morning Everybody,

Well it would seem that our problem has been solved, i will confirm this tomorrow after the official test.

When they stripped down the brakes, i believe they found that one side was seized which i assume was causing the imbalance. However the lack of efficiency was down to an airlock in the lines. After a thorough bleed through the brake efficiency has shot up so hopefully it is not the doom and gloom we thought.

What i don't understand is why the airlock occured, surely this is a sealed system?

Thanks and regards

Chris

My bus number (if any): RML2719

Fluid level low = pump can suck in air. Incorrect hydraulic filter fitted = pump can suck in air. Accumulator seals leaking = air pressure can pass seals into fluid side. Wheel cylinder weeping = air can enter fluid. Any pipe union weeping or not tight = air can enter fluid. Hydraulic pump seals weeping = air can enter fluid. Footbrake valve faulty = air can possibly enter fluid. Low pressure switch faulty = air can enter fluid. Flexible hydraulic pipe porous = air can enter fluid. Test points, etc. etc.

Bleeding RM brakes is not a five minute job. Nor are two litres of oil likely to be sufficient.

I just hope whoever does or has done the work used the correct oil and NOT hydraulic brake fluid! You should use the correct oil; I use HYD22 which is readily available from decent oil stockists. It is near enough the original spec Tellus oil.

My bus number (if any): RML2532