911 SC Brake Fluid Resevoir Dropping

[TheBaywatchKid]

I've noticed in my SC that my brake fluid is dropping a little over the past month. Still 75% full, but it was 100% full a month ago. Check the pedal box, and can't see any sign of leakage. And the frunk shows no sign either. Is this normal, or something I should be worried about? 

 

Cheers!

[Stepo]

I never see mine go down much over long periods, 25% over 1 month would have me concerned and booking it in for a check.

[P-Kay]

When was the last time it was flushed? If not for a lonog period, then it is mostly water, therefore evaporation.

[TheBaywatchKid]

16 hours ago, Stepo said:

I never see mine go down much over long periods, 25% over 1 month would have me concerned and booking it in for a check.

Noted. Thanks mate, was planning on bringing in soon will just mention.

 

2 hours ago, P-Kay said:

When was the last time it was flushed? If not for a lonog period, then it is mostly water, therefore evaporation.

I actually don't know. I only have the car a month. I know the car wasn't used much before I bought it, so it could just be that now im using it daily, its evaporating the water. I'll keep an eye on it! Thanks  lot!

[Buchanan Automotive]

You may find that the ( possibly old ) brake master-cylinder "could" be weeping brake-fluid into the brake booster , we had a 964 here recently that the old brake master cylinder had weeped/leaked brake fluid into the booster & this wrecked the diaphragm in the booster  , in this situation the brake booster becomes an brake fluid holding tank that no one wants & this does not do the booster any favors

It would be advisable to remove the old brake master cylinder and inspect for brake fluid "wetness" at the end of the master cylinder

Note 1 }    The brake master cylinder on a 911SC or 3.3 Turbo protrudes into the booster & the master cylinder if it leaks externally ( not super common ) can leak into the booster

Note 2 }   The normal brake master ( in old age ) issue is an internal leak , meaning the brake pedal sinks to the floor under a constant light ( foot on pedal ) pressure

Note 3 }  Naturally if there is no brake booster ( earlier 911 series etc ) the the external leak will be more noticeable because there will be no brake booster hiding the external leak 

Regards
Bruce Buchanan

[TheBaywatchKid]

47 minutes ago, Buchanan Automotive said:

You may find that the ( possibly old ) brake master-cylinder "could" be weeping brake-fluid into the brake booster , we had a 964 here recently that the old brake master cylinder had weeped/leaked brake fluid into the booster & this wrecked the diaphragm in the booster  , in this situation the brake booster becomes an brake fluid holding tank that no one wants & this does not do the booster any favors

It would be advisable to remove the old brake master cylinder and inspect for brake fluid "wetness" at the end of the master cylinder

Note 1 }    The brake master cylinder on a 911SC or 3.3 Turbo protrudes into the booster & the master cylinder if it leaks externally ( not super common ) can leak into the booster

Note 2 }   The normal brake master ( in old age ) issue is an internal leak , meaning the brake pedal sinks to the floor under a constant light ( foot on pedal ) pressure

Note 3 }  Naturally if there is no brake booster ( earlier 911 series etc ) the the external leak will be more noticeable because there will be no brake booster hiding the external leak 

Regards
Bruce Buchanan

Thanks for the super detailed description Bruce! Under constant light pressure, the brake pedal doesn't sink to the floor, so hopefully not an internal leak. Going to take a much deeper look this weekend. Will remove brake master cylinder and see what lies beneath!

 

Thanks again, really appreciate it! Will have to pop in next time I'm heading north.  

[Buchanan Automotive]

If the brake master cylinder is leaking externally ( meaning leaking brake fluid into the booster ) , you will need a new brake master cylinder  & probably a brake booster if there is brake fluid in the booster .

[Merv]

If it was me , the first thing I would be doing is flushing out the old fluid and replacing it with fresh (as P-Kay suggests). Do you have access to a Motive Pressure blender, or similar?  Makes it easier.  Then each wheel.  If there is a lot of water in that fluid it will damage the callipers and the MC. You can check the quality of the fluid as it comes out. Should be done annually and this process may show up the leak, if you have one. My favourite fluid is no longer available (Bendix Blue).  It was great as the change in colour at the bleed point let you know when you had flushed all new fluid through.  It also would turn from blue to a yellow/green colour when inevitably contaminated hydroscopically by moisture drawn from the atmosphere.  

[TheBaywatchKid]

I don't .. but will have a look around. New brake fluid seems like the go anyway, will do no harm and it'll be good to see what condition the old fluid is in. Will give that a go and see from there. Thanks again!