Before I Bozo my brakes could someone point me in the right direction regarding the brake pressure accumulator.

The manual is talking about releasing pressure from the accumulator vent valve. Is this necessary and if so how is it done? Do I need a special tool? Then it talks about opening the bleed valve on the accumulator which seems staight forward but if I do this will I need the brakes reset with a Hammer?

Could I just bleed fluid from the respective wheels with a pressure bleeder and accomplish the same task?



Thanks in advance.

 

Use the bleeder on the accumulator, not the fitting with the screw on cap. If you just do the calipers, you'll miss a lot of fluid. Pumping the pedal a bunch with the car off will depressurize the accumulator so it won't squirt everywhere when you open the bleeder on it. I use the Griot's Garage vacuum bleeder without a Hammer and have no problems. You can get more fluid out if you hook up to the accumulator bleeder, then run the boost pump while keeping the reservior full. Be sure to bleed the inner caliper bleeders too.

 

911/Q45

Thanks that sounds good. The screw cap had me going.

 

Time to do my first fluid change on a 911 with the booster circuit. I found this thread and am a bit confused. According to the manual the brake pedal should not be used to depressurize. Why is this? Seems that the only reason not to do it this way would be to speed up the process by using the system pressure to start the fluid change at the accumulator (rather than use the booster pump exclusively). I'd prefer not to risk a high pressure brake fluid mess so the idea of using the pedal to depressurize is more appealing. I'd just like to confirm that doing so won't creat other problems. Would appreicate any BTDTs.

Thanks,

Kevin

 

Hi Kevin,

As you can tell from my post I am no expert but that is exactly what I do with no problems. It takes quite a few pumps of the brake pedal but it works fine and no issue with pressure at the accumulator. The main thing is not to totally drain the system dry. Since this post I have done this about a dozen times with no problems.

Good luck.

 

Thanks Keith. Over the weekend I used the 'pedal' method to depressurize. Couldn't road test until tonite since my wheels were out getting new rubber. After several 70 - 0 stops in a row, everythings seems to be just fine.

Interestingly, my pressure bleeder seemed to work best at 22 psi. Quite a bit more than I was used to. Does that seem to be the norm on a TT?

Kevin

 

Again no expert here but the manual references approximately 1.5 bar for pressure so 22psi is in the ballpark. I think I generally go with around 15. It is slow but I was just being conservative. Sounds like all went well.