It's a shame too that Gardner engines are no longer a feature on new buses or trucks. Another fine part of British industry gone. I always preferred Olympians with Voith gearboxes and the Dennis Dominators and MCW Metrobuses with the same driveline.
This hiss has nothing to do with the gearbox as suggested in previous comments. The bus has a hydrocyclic gearbox which by its very name tells you its opearted by Oil pressure not air. The noise you are hearing is actually the air operated throttle dump valve. This dump valve removes the high pressure air from the throttle cylinder on the engine during each up change, this gives the bus a smooth gear change and prevents the lock up of two gearbands. The noise is totally normal.
Originally all had the throttle dip/dump valve fitted. Our semi auto ones at West Riding did it but they gradually stopped working. They stopped driver abuse which was a problem when drivers slammed them thro the box.
I like these buses too, probably my favourites. The back also has the warm engine smell of the Gardner engine which is character. I like the B7TL's with a Voith gearbox and the ALX400 like in Liverpool are my favourites. They are bland if they have any other gearbox, but the Voith really gives a nice gear change and whine.
I remember the ex GMT olympians hissing through gear changes but some tine in mid 90 towards around 255 to 8 for the absolute last example still in manchester the gears sounded all wrong and no hiss between the gear changes either. The one that passed to first manchester were dreadful towards the end of service espicailly in the last few years. They often slipped out of 1st Gear.
Yes they should do I hated it when the hiss went out the gears at every gearchange. Many Hydracylic gearboxes got bodged when the buses were getting towards the end of service including many wrong gearchanges.
exactly how automatic Olympians SHOULD drive - superb!
It's a shame too that Gardner engines are no longer a feature on new buses or trucks. Another fine part of British industry gone. I always preferred Olympians with Voith gearboxes and the Dennis Dominators and MCW Metrobuses with the same driveline.
This hiss has nothing to do with the gearbox as suggested in previous comments.
The bus has a hydrocyclic gearbox which by its very name tells you its opearted by Oil pressure not air.
The noise you are hearing is actually the air operated throttle dump valve. This dump valve removes the high pressure air from the throttle cylinder on the engine during each up change, this gives the bus a smooth gear change and prevents the lock up of two gearbands.
The noise is totally normal.
This is how you can tell what gearbox is fitted. Fully auto ones hiss semi auto ones don't.
Originally all had the throttle dip/dump valve fitted. Our semi auto ones at West Riding did it but they gradually stopped working. They stopped driver abuse which was a problem when drivers slammed them thro the box.
I like these buses too, probably my favourites. The back also has the warm engine smell of the Gardner engine which is character. I like the B7TL's with a Voith gearbox and the ALX400 like in Liverpool are my favourites. They are bland if they have any other gearbox, but the Voith really gives a nice gear change and whine.
I remember the ex GMT olympians hissing through gear changes but some tine in mid 90 towards around 255 to 8 for the absolute last example still in manchester the gears sounded all wrong and no hiss between the gear changes either. The one that passed to first manchester were dreadful towards the end of service espicailly in the last few years. They often slipped out of 1st Gear.
Some of the old Wilts and Dorset ones used to do that
So did the Bournemouth yellow buses olympians
Yes they should do I hated it when the hiss went out the gears at every gearchange. Many Hydracylic gearboxes got bodged when the buses were getting towards the end of service including many wrong gearchanges.
5th March 1985
if it didn't sneeze then it wouldn't be changing properly! 😊
When they don't sneeze the throttle dip valve has gone and makes the bus overrev like mad.