Welcome to BigCarClub!

Not logged in!

Hey there, welcome to BigCarClub!
You don't need to be logged in to view the forum but the experience will be so much better if you are! Users can login or if you don't have an account already, you can create one for free by clicking the Register link in the top right corner of this page.


hissing under dash

Started by daddyfixit, October 26, 2023, 05:38:48 PM

Previous topic - Next topic

0 Members and 1 Guest are viewing this topic.

problem;  A constant hissing under dashboard from brake servo; touch pedal and it goes away till you next brake ? 
I took car for new clutch this morning, got there and he had to rebook me.  So driving in traffic and The brake pedal went rock hard (no servo) but I kept trying brakes for rest of journey and had no problem.

1. deffo servo failure, but wasn't there an issue were the ends of servo pipe spilt off causing an air leak ??   its an X-reg so I can appreciate it may have split (not looked yet)

but the fact it can be heard inside car bothers me--I know brake pedal linkage to master cylinder is under dash, but what kind of a job is it to change a servo ??

I'd say the noise from that area kind of makes sense in that the servo (aka brake booster) is just forward of the pedal.
Just had a quick shufty at the hyenas manual and at least part of the servo can be accessed from inside the cabin when the lower fascia is removed.
the actuator shaft is connected to the pedal lever.
and you have to remove the nuts down there to get it and the master cylinder out of the engine bay.
Only inspection will tell but it's possibly a worn leaking servo unit sucking in air or the pipe from the vac pump on the cylinder head is possibly failing at the servo end
(I'm assuming its a deisel)

thanks Regw;

  Yes, its a Pd 90hp model (the baby one !)      But my mrs and kids say there has been a hissing from the brake pedal area for years, which I could not ear as I have tinnitus!
  But on Tuesday it had a new dual-mass & clutch fitted----the car feels, sounds and drives like a new car now but now I can hear the hissing noise. I have noticed that on the 2nd or 3rd application of the brakes, the pedal goes rock hard until you leave it a few seconds then its all ok again ?

I have been reading a post about main servo pipe splitting so I am going to try and have a nose at that when the rain eases off (later this year )

thanks for replying.