Brake master overflow?

bontrager_steel · Post by **bontrager_steel** » Wed Sep 07, 2005 9:26 pm

Well - I am in the process of putting my brakes together, and it looks like I need to take them back apart again. 66 roadster w/ a single reservour and speed bleeders on all 4 wheels.

I am using a mightvac bleer and starting bleeding from rear left, to rear right, to front left to front right, to bleeder on master. Doesn't seem to be any air in the system. (FYI - just bled my clutch and no problem what so ever)

I have went through just under 2 liters of fluid because I thought I had a wicked air bubble trapped somewhere (since everything is new), but I still have absolutely no pedal pressure. Pumping repeatedly also still gives no pedal pressue.

Just noticed that when I pump the pedal, the fluid in the reservour actually rises (when shouldn't it be going out to the pistons?) Anyhow - if anyone has any ideas, please let me know. Otherwise going to be tearing apart the master cylendar tomorrow since I think it has to be the culprit.

Thanks -

TR · Post by TR » Wed Sep 07, 2005 9:38 pm

Make sure to bleed the master...You may have air trapped in it. Attach a short hose to the bleeder on the master and run it right back into the cup. Pump away...

Although, it sounds like your master may be dead...

Post by **dbrick** » Sat Sep 10, 2005 10:03 pm

I'm with TR on that one. You can also get a 12 inch section of steel brake line, make sure fittings match, and hook it where the main brake line goes and make a loop back up to the reservior.

I think the single master cylinders is relativly inexpensive, compared to dual, and considering you only have a single circuit brake system, I'd just get a new one if there is any doubt at all.

It's amazing how much trust we put into a bunch of 29 cent rubber cups and seals to stop the car.

Post by **23yrRebuild** » Sat Sep 10, 2005 11:04 pm

Sometimes it's easier to bleed them if you have a helper pumping the pedals.

TR · Post by TR » Sat Sep 10, 2005 11:35 pm

Mike,

Your thinking along the right lines, but rest assured that with a good bleeding, you'll get the air out of the slave. With vigorous bleeding, the oil enters the slave so quickly that it will mix with any air bubbles present and eventually, you'll bleed them out.

TR

Post by **dbrick** » Sun Sep 11, 2005 9:49 am

Wouldn't that be reinventing the wheel (cylinder)?

Post by **23yrRebuild** » Sun Sep 11, 2005 5:16 pm

Yup!

TR · Post by TR » Sun Sep 11, 2005 10:31 pm

A good dose of what everyone has described on this thread and others. I'll describe what I have had luck with:

Make sure you never let the level in the master get low enough to draw air, if this happens pump out the line till you get that air out. Have your pumper watch the level, it is their job not to pump if it gets low. Attach a clear tube to the bleeder nozzle and run it up at least 6" before back down and into a waste container so you can see the fluid and air bubbles. Set the bleed screw so that the helper feels a little resistance, don't have it wide open - just a slight turn from closed does the trick. Have a helper pump the brakes steadily, smoothly and slowly with a couple of rapid pumps followed by a couple more slow ones when no more air is coming out. I always lock the bleeder in the middle of a slow pedal stroke without warning the helper so that I know air is not sneaking back in. Speed Bleeders reduce the need for this, but I stick with the method like an old dog...

Bleed the master
Starting with the longest line route working toward the shortest...
Bleed the drivers rear wheel most of the way
Bleed the passenger rear wheel most of the way
Bleed the drivers front wheel most of the way
Bleed the passenger front wheel most of the way
By most of the way, I mean bleed it till the bubbles are sporadic...
Go back and repeat each wheel in order (the master doesn't need any further unless the level got low), only moving on when there are no bubbles.

At this time you should have a perfectly functioning system. Sometimes I'll let everything sit for an hour or drive the car a day or two and repeat the sequence one more time. Then the brakes have a solid pedal feel every time. If you get any changes, hunt down the leak (typically a rear slave) or you will always have trouble.

Brakes are serious business, make sure you are confident of them and they are working great before leaving the driveway...Good Luck! TR

Post by **dbrick** » Sun Sep 11, 2005 11:00 pm

I forgot to mentin, I used a Motiv power bleeder, about $60.00. Although I am returning it, because it is awkward to hook up and not very well made, it bled the brakes and clutch perfectly in less than 5 minutes, once I got it to seal.

Post by **23yrRebuild** » Mon Sep 12, 2005 10:10 am

Deleted

bontrager_steel · Post by **bontrager_steel** » Mon Sep 12, 2005 12:04 pm

Hey guys - thanks for all the feedback.

Got it working, there is actually a secondary spring and plunger on the end of the main shaft running underneath the reservoir (sorry I don't know the correct part names)

Anyhow - mine was just gummed up and not moving. Once I noticed there was a spring there (I silently commited to purchase a new master) and started prying : ) Luckily it freed up......

I added a pic of the dissassembled master here for future ref.

http://www.311s.org/phpBB2/album_pic.php?pic_id=155

Dbrick - in respose to your question about a good way to bleed. I always uses a hand bleeder in conjustion with somebody at the pedal. Basically I maintain contant vaccum on the bleed screw, have my beautiful assistant (this time my little brother!) pump the brake pedal. the combination of the two I think helps ensure no air getting into the lines. Also, I think it pulls the fluid through the lines pretty quickly. Anyhow - just my 2 cents.....

Post by **dbrick** » Mon Sep 12, 2005 11:23 pm

same exact thing happened on my dual master cylinder, I should have picked up on that, no rear brakes (in my case) low pedal and squirting up into the reservior. My secondary piston was stuck in the bore. I thought the single was different internally. Great you found it.