Hissing from behind dashboard ?

[hixsy]

hi guys, recently got hold of me t25 87 transporter. goin for the full camper covert obviously, but recently its been makes a gradual increasing hissing noise behind the instrument panel, where the master cylinder is ? It seems to increase with the engine to a certain point then stop, ive found that if i pump the brakes it will keep hissing, im kinda hoping its a simple problem to fix but as ive found so far with the van it normally leads to a bigger job, any ideas/remedies greatly appreciated thx..

P.S. as first time T25'r ill just show ya wat it looks like now before the respray which is happening in a few weeks




thx in advance

[clartsonly]

nice van dude.

does it make any hissing when the clutch is pressed they share the same master cylinder the clutch takes from about halfway up so when that fails the brakes will still work.. it might just be air.. carefully remove the dash cover and you can access the top of the master cylinder and cap etc..

good luck

[Gadders]

Nice van...

respray

Leave it as it is,looks cool

[Rozzo]

it'll be the vacuum pipe that goes directly to the brake servo(or could be the servo itself perforated), which is behind the dashboard on the end of the master cylinder. it'll be "sucking" air which will affect how well the brakes work and also how well the engine runs

[kevtherev]

what he said..

[peasant]

Could be something as simple as a leaf or other debris stuck in the vents or blower box (unless of course it also hisses when you're standing still)

[hixsy]

it'll be the vacuum pipe that goes directly to the brake servo(or could be the servo itself perforated), which is behind the dashboard on the end of the master cylinder. it'll be "sucking" air which will affect how well the brakes work and also how well the engine runs

ok thank you, how do i go about stopping it m8 ?

[hixsy]

Could be something as simple as a leaf or other debris stuck in the vents or blower box (unless of course it also hisses when you're standing still)

thx ill check that too, it dont hiss when standing still

[Rozzo]

it'll be the vacuum pipe that goes directly to the brake servo(or could be the servo itself perforated), which is behind the dashboard on the end of the master cylinder. it'll be "sucking" air which will affect how well the brakes work and also how well the engine runs

ok thank you, how do i go about stopping it m8 ?

first find the leak,, then see whats needed to fix it. oh and you did say it sucks more when you press the brake pedal which it will presumable also do when you're standing still with the engine running.

[kevtherev]

Pull off the dash pod and it's all there.. mate

[hixsy]

ok then thanks, 2moro i rip out the instrument panel.......again......

thx all ill let ya know wat i find .... /shudder

[Rozzo]

it'll probably be the rubber seal where the pipe pushes into the servo or something simple like that m8.. could even be as simple as the pipe being forced sideways offline by something else.
good luck with it.

[Mr Bean]

Don't listen to them. You have clearly got a snake trapped in the dashboard!
A rather bored andchildish Wolfie

[xpress]

hiya, i noticed a hissing with the top cover off and the wire out of the master cylinder cap. if i put my thumb over the contacts where the wire plugs in, the hissing goes away. is this normal? if i put my thump over the recess where the wire plugs in when i pedal up and then take my thumb off it when i pedal down, i can actually hear brake fluid trickle around underneath the o/s front tyre.

also am i right in thinking that this might be an air vent or something and that the system is not pressurised? am i right in thinking that if the cap is off, the brake system doesn't get any air in it unless the fluid goes below minimum?

[kevtherev]

I think what you're describing needs to be seen and heard or you could re write it.
Hydraulic fluid does not "trickle around" in my experience. It only transfers a force, it does not move at all in the pipes.
you either have a spongy pedal because of air or it's hard



braking systems are not pressurised, they are assisted by the vacuum servo, this adds more force to the arm that pushes the piston in the cylinder.
Air gets in if the level goes down, whether the cap is on or not