Help identifying unusual noise in Class 158 carriage

[Bodie]

Travelling yesterday on Scotrail's 158706, I heard a noise inside the carriage. A noise which was near constant. Every five seconds approximately.

It sounded like something venting. A 'tsssh' sound.

I moved to the next carriage as the noise was bugging me and thankfully found that carriage didn't have that noise.
I don't know which carriage number the noise was in 57706 or 52706. It was the carriage that has the toilet with the electronic door.
I was sat at the drivers cab end, in the last row of seats.
The next row of seats back along the aisle was where the noise was coming from.
Underneath those seats are some grey coloured boxes. I believe these were the source of the noise.
The actions of the train (ie. Slowing down, accelerating) didn't alter the noise.

Thanks,

Bodie

 

[Teflon Lettuce]

Travelling yesterday on Scotrail's 158706, I heard a noise inside the carriage. A noise which was near constant. Every five seconds approximately.

It sounded like something venting. A 'tsssh' sound.

I moved to the next carriage as the noise was bugging me and thankfully found that carriage didn't have that noise.
I don't know which carriage number the noise was in 57706 or 52706. It was the carriage that has the toilet with the electronic door.
I was sat at the drivers cab end, in the last row of seats.
The next row of seats back along the aisle was where the noise was coming from.
Underneath those seats are some grey coloured boxes. I believe these were the source of the noise.
The actions of the train (ie. Slowing down, accelerating) didn't alter the noise.

Thanks,

Bodie

I don't have knowledge of rail engineering, but on a bus that is usually indicative of either a faulty valve or a faulty compressor in the air systems...

 

[DanDaDriver]

The compressors will be constantly running on a 158.

When the main air res gets to a certain pressure (7.7BAR IIRC)then the compressor unloader will vent it to stop it getting dangerously high.

There’s also safety valves (at around 8 and 9BAR I THINK ,but I can’t remember exactly) in case the unloader fails.

You can isolate the unloader valve if it sticks open to stop it dumping all your air. I doubt they’d let it remain in service if it was though.

That could be the noise you heard.

 

[robbeech]

Definitely sounds compressed air related.

 

[trebor79]

A few years ago I was on the sleeper to Fort William and enjoyed dropping the window and enjoying the fresh air and view in the morning. Gave up after a few minutes because the 66 was doing exactly this and it was really irritating for some reason. Probably because I was a bit tired having slept fitfully!

Apols for thread drift.

 

[Mordac]

A few years ago I was on the sleeper to Fort William and enjoyed dropping the window and enjoying the fresh air and view in the morning. Gave up after a few minutes because the 66 was doing exactly this and it was really irritating for some reason. Probably because I was a bit tired having slept fitfully!

Apols for thread drift.

Is there any other way to sleep on a sleeper train?

 

[edwin_m]

Something similar for the opposite reason in a 158 a few years ago*, when there was a leak in the system. Rolling down through Chinley the engine wasn't driving the compressor enough to overcome it, so when the pressure got a bit low the driver kept having to stop and rev the engines to pump it up.

*Last days of Central or first days of EMT, when their 158s were dying left right and centre.

 

[trebor79]

Is there any other way to sleep on a sleeper train?

Yes, there is:
Not at all