Brakes - at my wits end

[sgroer]

The only thing in between my son and I driving project Karl the 911 outlaw are the brakes. Literally everything else is done and if the brakes were working we would have gone for our first drive by now.

The brakes are Brembo GT and we upgraded to a 930 Master Cylinder due to the size of the calipers. We use a motive power bleeder so we have not bench bled the Master. No matter how much we bleed, no matter how much we flush the pedal never gets firm. We get clear fluid at the calipers, no bubbles when pressure bleeding them.

When I hit the brakes, the brake reservoir gurgles. Bubbles come up and the pedal goes to the floorboard. I disassembled the master cylinder and looked at the seals, they look totally fine and the cylinder walls weren't scored. But, I can only conclude that the MC is defective - I've never had an issue like this. It is SOOOOOO frustrating.

Additionally we pulled everything out (again, again, again) and removed the bracket from the booster. The booster is also clearly leaking at the piston, so I will get that addressed, but i don't believe that should have affected the ability to bleed the brakes.

We want to drive Karl!!!!

[Funracer]

Ok this is a dumb one but it happened to me on my sons Sebring about 10 years ago. Same symptoms you describe over and over. After two days gave up and took it to a brake shop. They figured it out in 1 minute. On some cars (don’t know about Porsche) calipers can be mounted on the wrong side. Left on the right and right on the left. This puts the brake line low on the caliper instead of at the top where the bubbles go. They are marked L & R but I did not know that. I do now.

Anyway just throwing it out out there. Good luck.

[sgroer]

Originally Posted by Funracer

Ok this is a dumb one but it happened to me on my sons Sebring about 10 years ago. Same symptoms you describe over and over. After two days gave up and took it to a brake shop. They figured it out in 1 minute. On some cars (don’t know about Porsche) calipers can be mounted on the wrong side. Left on the right and right on the left. This puts the brake line low on the caliper instead of at the top where the bubbles go. They are marked L & R but I did not know that. I do now.

Anyway just throwing it out out there. Good luck.

Thanks for the response - yeah the bleed valves are on top - admittedly the rears were reversed, but we realized it before we started filling the system with fluid.

[dannobee]

Why didn't you bench bleed the master cylinder? I'd start there first, even though it means taking it back off and bleeding it in a vise.

[sgroer]

Originally Posted by dannobee

Why didn't you bench bleed the master cylinder? I'd start there first, even though it means taking it back off and bleeding it in a vise.

The master cylinder is off again now and I was going to do that next . I had read that it is not necessary when using a power bleeder.

[blucille]

I had the gurgling too. It turned out the vent tube from the reservoir was plugged. Disconnect the vent tube at the reservoir and run a temporary into a catch can or out thru a grommet and see what happens.

[TwoBluPorsches]

I had a bubble in a motorcycle master cylinder that was impossible to clear using a couple normal bleeding methods after I had installed it on the handlebar and to the remaining brake system.

Eventually I took it off for bench bleeding,
Since I was able to change the orientation drastically and I wasn’t dealing with a couple feet of brake line I was able to make it work.
Then when I installed the ‘filled’ MC I was able to bleed as normal.

I know it’s not exactly the same situation but making sure the master works well on the bench might be a good step if you haven’t done that.


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[Dpmulvan]

You do know that Brembo has two bleeder screws per caliper? you do the outside first, then the inside. Not trying to insult your intelligence just thought you might have overlooked.

[sgroer]

Originally Posted by blucille

I had the gurgling too. It turned out the vent tube from the reservoir was plugged. Disconnect the vent tube at the reservoir and run a temporary into a catch can or out thru a grommet and see what happens.

Unbelievable. I read your post and went to the garage this morning. The brand new overpriced braided line had a chunk of rubber in it from manufacturing. Never thought to check brand new line for obstructions.

Now to put it back together. And I can’t thank you enough! This should do it.

[Funracer]

Originally Posted by sgroer

Unbelievable. I read your post and went to the garage this morning. The brand new overpriced braided line had a chunk of rubber in it from manufacturing. Never thought to check brand new line for obstructions.

Now to put it back together. And I can’t thank you enough! This should do it.

Did you get it sorted?

Isn’t that just annoying as all. Had it or similar happen so many times in the past couple of years its just my policy now to precheck everything that goes on the car, whether its a new part or one that has been sent in for rebuild.

[berndtj]

Originally Posted by Dpmulvan

You do know that Brembo has two bleeder screws per caliper? you do the outside first, then the inside. Not trying to insult your intelligence just thought you might have overlooked.

I know I’ve been burned by this. Man was I frustrated, followed by embarrassed/ashamed .