Brakes

[zhap135]

Hello , I'm setting up teh brakes on my S7. I have what i believe is a new brake cylinder. Have bled the front brakes (at least managed to push fluid through) and now am having fun with the rear (drums). There is no resistance in the brake pedal and I can hear a hiss of escaping air - hard to identify exactly where from. Was thinking the seals on the cylinder might have gone - before I buy a new cylinder has anyone got any ideas?

 

Cheers all

Edited April 2, 2023 by zhap135

[Sparepart]

Assuming that your engine is not running and you have a brake servo then the hiss is possibly the diaphragm in the servo forcing air somewhere like back to the inlet manifold. Disconnect the vacuum pipe and listen if the hiss changes or disappears. If this is the case then it can be ignored from the point of view of bleeding the brakes.

Edited April 8, 2023 by Sparepart
spelling

[HAWKNORTH]

If the seals have gone in either the master or brake cylinders you should see evidence in the form of leaking brake fluid. No resistance in the brake pedal travel and an audible hiss points to the servo as stated by "spare part" above.

[zhap135]

Gents

On 4/8/2023 at 12:48 PM, Sparepart said:

Assuming that your engine is not running and you have a brake servo then the hiss is possibly the diaphragm in the servo forcing air somewhere like back to the inlet manifold. Disconnect the vacuum pipe and listen if the hiss changes or disappears. If this is the case then it can be ignored from the point of view of bleeding the brakes.

 

On 4/8/2023 at 5:15 PM, HAWKNORTH said:

If the seals have gone in either the master or brake cylinders you should see evidence in the form of leaking brake fluid. No resistance in the brake pedal travel and an audible hiss points to the servo as stated by "spare part" above.

Thanks Gents. Does this mean that there is not necessarily a problem? it's worht trying wth the engine running and the issue may not be evident?

[Bob Tucker]

If there is no resistance to the pedal (does it go all the way to the floor?) theres probably still air in the rear lines or cylinders.
The only way I can properly bleed my rear brakes(2B) is to jack the rear of the car as high as possible, otherwise I cant pump out the air in the pipe running from front to back. Pumping just moves the bubble backwards and forwards in the line. Leave it jacked up for an hour or two to get the bubble to the rear. I'd suggest getting a hard pedal without the engine running first, than investigate the air hiss. HTH