Tom Mat

I have just completed the replacement of my master cylinder in my 77 911. I was proceeding to pressurize the system and bleed my brakes when I encountered a problem. Using a Motive brake bleeder I could not pressurize the system from the reservoir. I can hear the air escaping. It appears to be coming from the power brake area. I cannot narrow it down. I know there was an o-ring on the old cylinder but the new cylinder came with a gasket. Can anyone tell me if the 0-ring should have gone on top of the gasket? The o-ring was within the same spot that the new gasket was on the replacement cylinder?

Any ideas?

Jim Richards

Tom, my 73E has a vent line on the brake fluid reservoir. I have to plug this before pressurizing the system to bleed it. Is it possible that you have to do likewise?

Bill Gregory

Well, if it were me, and an o-ring was there before, I'd use an o-ring again, and not a gasket. But I don't think that's your problem. Usually, when bleeding the brakes with a pressurized brake bleeder, you do it one of two ways: you either put brake fluid in the brake bleeder tank or sometimes you just use the brake bleeder to pressurize the system. I'm guessing you are trying to pressurize the system using the Motive brake bleeder without fluid in the brake bleeder tank. Did you clamp the overlow line that exits the brake fluid reservoir?

Tom Mat

Thanks for both of your suggestions and I did not have the overflow line clamped. I will try that tomorrow. I'll let you know if I was successful.

</font><blockquote><font size="1" face="Verdana,Tahoma,Helvetica">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Helvetica">Originally posted by Tom Mat:
<strong>I have just completed the replacement of my master cylinder in my 77 911. I was proceeding to pressurize the system and bleed my brakes when I encountered a problem. Using a Motive brake bleeder I could not pressurize the system from the reservoir. I can hear the air escaping. It appears to be coming from the power brake area. I cannot narrow it down. I know there was an o-ring on the old cylinder but the new cylinder came with a gasket. Can anyone tell me if the 0-ring should have gone on top of the gasket? The o-ring was within the same spot that the new gasket was on the replacement cylinder?

Any ideas?</strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">