Man L2000 hydraulic seat air problem

[John Russell]

I've just collected a motorhome built on a 2001 Man L2000 truck chassis.

The two front seats are on hydraulic suspension and can be raised and lowered, and fully rotated to the hab area.

When the seats are raised, without a passenger's weight, the air in the suspension leaks out until the vehicle's air tank is empty.

If the seats are fully lowered, the air tank maintains pressure.

This means that if using the seats in the hab area, they have to be lowered before you can stand up. Which is awkward.

And that the suspension has to be reset every time before driving.

Is this normal? Can anyone who is familiar with this chassis advise?

Tia.

 

[funflair]

Hi John

First off "congratulations" secondly re the air seats I believe that they can be prone to loosing air but I don't know why or how to fix it, soapy water and a brush to start if you can get in, jongood any ideas, I am sure Philip said they leak/leaked.
.

 

[jockaneezer]

Don't have any experience of the truck seat, but I'd be looking for a loose fitting, split airbag or a split pipe, all of which could leak when in the fully extended position, but the leak might be "nipped shut" in its lower position ?On the pneumatic seat on our tractor, it has a small compressor that fills the miniature suspension airbag, all this and the pipework are visible if you remove the rubber "bellows" that surround the seat base. I had to replace the small shock absorber that damps out the seat movement and it was evident that some of the pipework can be prone to chafing after a while.

 

[John Russell]

Thanks for the thoughts.

It isn't exactly a leak. There is an exhaust hose for the air, which allows air out when the seat is dropped.

However it also lets air out if there is no weight on the seat.

I would have thought that there would be a 3-way valve to connect either the air tank to raise the seat, the exhaust to lower it, or neither to hold the pressure.

In which case the seat wouldn't lose pressure when you stand up from the seat.

Maybe someone with the same seats can confirm the behaviour?

 

[John Russell]

Problem diagnosed.

These seats should maintain a constant level in use; when you stand up the seat automatically releases pressure; when you sit down it re-pressurises to maintain its height.

When the vehicle is started, the seats should return to their previous settings.

A bit of investigation showed a broken plastic valve on the faulty seat, which was intermittently leaking and not reliably separating the air supply from the exhausts. Dropping the seat fully seems to prevent the air loss.

Another valve is on its way which should solve the problem.

Thanks to everyone for the help and advice.

John

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