Brakes?

[Rabbitoh]

Can anyone suggest a cause for a brake pedal ever so slowly sinking toward the toeboard, when stopped on a hill for a couple of  minutes. Have changed brake fluid and bled the system and there are no visible external leaks. I'm running a tin can fluid reservoir and a brake booster is fitted. I suspect the booster. Is this likely?
R.

[SEB]

Highly likely. I have had this problem before. Resolved it with a new master. The seals were worn and there was some damage to the wall. So if you held your foot down the system gradually lost pressure. If you have not done the slaves for a while it might pay to check those as well at this point.

Best regards,

Steve.

[Dr_Terry]

Hi Rabbitoh.

It's most likely the the master cyl primary cup seal.

The best lead is whether you are consuming fluid or not. With the master cylinder problem, you consume no fluid because the fluid stays in the master cyl.

If the leak was into the booster, your pedal would go the floor, say twice & your reservoir would be empty.

Dr Terry.

[Phantom]

I had exactly the same problem, bleed the brakes etc  didnt fix the problem , went and got a new master cylinder(77 dollars ) fixed no problems
                                          Cheers Rusty

[Rabbitoh]

Thank you gentlemen one and all.
That saves me suspecting the booster incorrectly.
Will attend to the master cylinder tomorrow (happen to have a new one sitting in the shed ).
It's great having access to other people's experiences and hard won wisdom via this forum.
R.