? about master cylinder
Thread Starter
Racer
Joined: Oct 2002
Posts: 470
Likes: 1
From: Kingwood TX
? about master cylinder
The directions for a new master cylinder state that if the push rod length is just right fluid will "erupt" when the brake pedal is pushed 3/8" to 1/2". On my car not only can you see no change in the fluid level when the pedal is pushed 1/2", you cannot even see a change after the pedal is pushed all the way down. Is there something wrong here or should I not expect to see a change on a '91?
Le Mans Master
Joined: May 2005
Posts: 7,354
Likes: 2,278
From: Central Maryland
Don't expect to see any change in the fluid level in the reservoir as you step on the pedal.
The piston will be pushing fluid that has already filled the working part of the cylinder under normal circumstances.
Only if the system develops a leak, or when the system does not return as much fluid on the upstroke as it was fed on the downstroke (e.g. as the pads wear and the caliper pistons move further out of their bores), should fluid be drawn from the reservoir to replenish the working part of the system.
Be well,
SJW
The piston will be pushing fluid that has already filled the working part of the cylinder under normal circumstances.
Only if the system develops a leak, or when the system does not return as much fluid on the upstroke as it was fed on the downstroke (e.g. as the pads wear and the caliper pistons move further out of their bores), should fluid be drawn from the reservoir to replenish the working part of the system.
Be well,
SJW
Team Owner
Joined: May 2002
Posts: 24,337
Likes: 25
From: San Diego , CA Double Yellow DirtBags 1985..Z51..6-speed
Tap the pedal quickly, you should see it spray out for the first bit of pedal travel.
What are you doing with your bad MC? Can I have it? I need it for experimentation.
What are you doing with your bad MC? Can I have it? I need it for experimentation.
Thread Starter
Racer
Joined: Oct 2002
Posts: 470
Likes: 1
From: Kingwood TX
That was a mis-type CentralCoaster. We replcd the Vacuum booster. We made the mistake of reading the installation instructions that came with it.The inst. gave this procedure which I never had ever seen or performed before.
Ignorance was bliss,now I have to fool around more with this conundrum.
Ignorance was bliss,now I have to fool around more with this conundrum.
Le Mans Master
Joined: May 2005
Posts: 7,354
Likes: 2,278
From: Central Maryland
Originally Posted by WEH 2000C5
That was a mis-type CentralCoaster. We replcd the Vacuum booster. We made the mistake of reading the installation instructions that came with it.The inst. gave this procedure which I never had ever seen or performed before.
Ignorance was bliss,now I have to fool around more with this conundrum.
Ignorance was bliss,now I have to fool around more with this conundrum.
What they are attempting to ensure with this procedure is that:
1. The pistons are not positioned so far back that, when you step on the pedal, a large amount of fluid is forced back up through the reservoir ports, into the reservoir (the "erupting" that was mentioned).
2. The pistons are not positioned so far forward that the reservoir ports are never uncovered when the pedal is fully released. If they are, it will prevent proper transfer of fluid to/from the reservoir/cylinder.
The whole idea here is that the reservoir ports should only be open when the pedal is fully relaxed. They should be closed off after only a minimal amount of pedal travel.
Be well,
SJW
Last edited by SJW; Dec 20, 2005 at 12:07 PM.
Team Owner
Joined: May 2002
Posts: 24,337
Likes: 25
From: San Diego , CA Double Yellow DirtBags 1985..Z51..6-speed
The piston movement rearward is limited by an internal clip. A short booster pushrod will just use pedal travel before reaching and moving the piston. The test covers this because if you don't get any fluid movement in the first bit of pedal travel, the pushrod isn't in contact with the piston yet.
The second part of what you said is true, the test is probably to ensure that you're booster pushrod isn't too long and forcing the piston past the reservior ports at zero travel.
So the 'erupting' is a good thing, and should happen at the first instance of pedal travel.. when the pistons are closing the ports.
Go here:
http://auto.howstuffworks.com/master-brake1.htm
The second part of what you said is true, the test is probably to ensure that you're booster pushrod isn't too long and forcing the piston past the reservior ports at zero travel.
So the 'erupting' is a good thing, and should happen at the first instance of pedal travel.. when the pistons are closing the ports.
Go here:
http://auto.howstuffworks.com/master-brake1.htm
Last edited by CentralCoaster; Dec 20, 2005 at 01:42 PM.
Le Mans Master
Joined: May 2005
Posts: 7,354
Likes: 2,278
From: Central Maryland
Originally Posted by CentralCoaster
The piston movement rearward is limited by an internal clip. A short booster pushrod will just use pedal travel before reaching and moving the piston. The test covers this because if you don't get any fluid movement in the first bit of pedal travel, the pushrod isn't in contact with the piston yet.
The second part of what you said is true, the test is probably to ensure that you're booster pushrod isn't too long and forcing the piston past the reservior ports at zero travel.
So the 'erupting' is a good thing, and should happen at the first instance of pedal travel.. when the pistons are closing the ports.
Go here:
http://auto.howstuffworks.com/master-brake1.htm
The second part of what you said is true, the test is probably to ensure that you're booster pushrod isn't too long and forcing the piston past the reservior ports at zero travel.
So the 'erupting' is a good thing, and should happen at the first instance of pedal travel.. when the pistons are closing the ports.
Go here:
http://auto.howstuffworks.com/master-brake1.htm
The "erupting" causes no harm, in any case. What's key is that the ports to/from the reservoir are exposed when the pedal is fully released. If this doesn't occur, the brakes can drag, or the working portion of the system can be starved for fluid -- neither of which is a good scenario.
Be well,
SJW
Thread Starter
Racer
Joined: Oct 2002
Posts: 470
Likes: 1
From: Kingwood TX
I,m very glad to learn this guys ,How did I miss this. I,m a licensed Aircraft mech,been doing my own car brakes for years & now 50 yrs later learn something I should have known A long time ago. That Vett sure ain't your fathers Cessna 150 .
Yep you whippersnappers can teach an old dog new tricks.I guess thats the brakes.
Warren
Yep you whippersnappers can teach an old dog new tricks.I guess thats the brakes.
Warren
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Le Mans Master
Joined: May 2005
Posts: 7,354
Likes: 2,278
From: Central Maryland
Originally Posted by WEH 2000C5
I,m very glad to learn this guys ,How did I miss this. I,m a licensed Aircraft mech,been doing my own car brakes for years & now 50 yrs later learn something I should have known A long time ago. That Vett sure ain't your fathers Cessna 150 .
Yep you whippersnappers can teach an old dog new tricks.I guess thats the brakes.
Warren
Yep you whippersnappers can teach an old dog new tricks.I guess thats the brakes.
Warren
It's been a mighty long time since anyone accused me of being a whippersnapper. But, if you've been doing brakes for 50 years, you surely have a few years on me, so I suppose everything's relative. In any case, I'm glad to hear the dialog helped out a bit. Good luck with the job.
Be well,
SJW