Replacing Master Cylinder... who can help??
Thread Starter
Navigator
Joined: Jul 2005
Posts: 9
Likes: 0
Replacing Master Cylinder... who can help??
Ahhhhh.... what to do?!?!?! I need to replace the master cylinder on my 77 vette because it appears that the rear hydraulic system failed... I am getting no assistance from the rear breaks when breaking
I was told it was due to a leak in the master cylinder.Replacing the master cylinder itself looks pretty straight forward. However, I do have some questions about how to refill the cylinder with fluid and how to bleed the brakes.
Questions:
Do I need to bench bleed the master cylinder? If so, can anyone explain the process and steps involved.
If not, how do I go about filling the mater cylinder reservoirs so I can bleed the lines?
-Thanks in advance!
Former Vendor
Joined: Nov 2005
Posts: 683
Likes: 1
From: Mounds View Minnesota
It's not too hard to replace the MC.
Yes you do need to bench bleed it;
There is probably a good article on wiki.corvettefaq.com about it.
But it goes kinda like this...
Clamp it in a vice by the ears that you mount it with.
get a bench bleeding kit from your local hardware store, either that or you have to make up som hard lines...
The lines ( bought or made ) screw into the master clyinder where the brake line is supposed to, then that tube goes up into the MC and is submerged in the fluid.
This is done for both front and rear.
Then you take a big screwdriver and push the MC's plunger all the way in, this will force air out of the MC piston. then release
Keep pumping the piston untill you don't think there is any air left, then do it that long again ( really)
Don't remove the bleed lines yet!
Then unbolt the old MC from the car, and bolt the new one on, then one at a time connect the brake lines to the new MC.
Then bleed the car's brakes.
Yes it's a lot of work!
But possible
Yes you do need to bench bleed it;
There is probably a good article on wiki.corvettefaq.com about it.
But it goes kinda like this...
Clamp it in a vice by the ears that you mount it with.
get a bench bleeding kit from your local hardware store, either that or you have to make up som hard lines...
The lines ( bought or made ) screw into the master clyinder where the brake line is supposed to, then that tube goes up into the MC and is submerged in the fluid.
This is done for both front and rear.
Then you take a big screwdriver and push the MC's plunger all the way in, this will force air out of the MC piston. then release
Keep pumping the piston untill you don't think there is any air left, then do it that long again ( really)
Don't remove the bleed lines yet!
Then unbolt the old MC from the car, and bolt the new one on, then one at a time connect the brake lines to the new MC.
Then bleed the car's brakes.
Yes it's a lot of work!
But possible
Instructor
Joined: Jun 2005
Posts: 248
Likes: 1
From: Apopka Florida
I'm not a pro at it but it was one of the first things I did on my project car. Getting the master in is easy. Connect the 2 lines then fill the master withing a 1/4 of the top. This is a lot eaiser with 2 people. If I'm not mistaken start with the drivers side front, then the passengers side front, drivers side rear and passengers side rear. Leave the top off the master while doing this because you will need to refill it as you bleed. Don't let the master go dry. Have your partner open the bleeding valve as you floor the brake several times to get the air out and close it before letting off the brake. Once the air is out continue onto the the next brake. your helper will not be happy with the mess just so you know. Make sure you refill the master after completion within a 1/4 of the top. You can do this with the tires on but it is a lot easier with them off. Good luck
Instructor
Joined: Jun 2004
Posts: 162
Likes: 1
From: Johnsburg IL
I read that sometimes after brake work or line replacement the distribution block needs to be reset (brass block mounted to frame). This is done by going 30 to 40 MPH and applying a hard brake a couple of times. Don't no the tech reasons why this.
Burning Brakes
Joined: Aug 2005
Posts: 1,126
Likes: 0
From: Hudson Falls, N.Y. 76 Vette Modified L-48
Originally Posted by 77fromHeaven
I was told it was due to a leak in the master cylinder.
Instructor
Joined: Jun 2005
Posts: 248
Likes: 1
From: Apopka Florida
Originally Posted by kb2fzq
Before you go thru the whole "swap out the M/C"..."who" told you it was bad?...and I assume you bleed the back brakes?...just to make sure you didn't have air back there?...would seem bleeding or re-bleeding would be the first step..
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Heel & Toe
Joined: Oct 2005
Posts: 22
Likes: 0
I ran into a similar problem w/the back brakes not working...coincidentally it was after locking up my brakes after some braniac pulled out in front of me while I was going 45mph. I found that the proportional valve was stuck. I could not free it up via hammer and ended up replacing the proportional valve. FYI just in case the problem persists.
Thread Starter
Navigator
Joined: Jul 2005
Posts: 9
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Before you go thru the whole "swap out the M/C"..."who" told you it was bad?...
I ordered the new ac delco MC and was planning on just putting it in and see what happens. Are there any quick things I should do first to get a better idea of if its necessary.
Thanks!
Racer
Joined: Oct 2005
Posts: 427
Likes: 0
From: Cary Illinois
If you've got the MC ordered and on the way, might as well drop it in I just did it a few weeks ago and it is really no big deal. You might want to switch out the proportioning valve while you're in there just to be safe.
Make sure you bench bleed the MC like everyone else has said. Buy a vacuum bleeder kit for $25.00 and bleed the lines all by yourself - I think it was a four hour (and eight beer) project
I just did it a few weeks ago and it is really no big deal. You might want to switch out the proportioning valve while you're in there just to be safe.Make sure you bench bleed the MC like everyone else has said. Buy a vacuum bleeder kit for $25.00 and bleed the lines all by yourself - I think it was a four hour (and eight beer) project
Burning Brakes
Joined: Aug 2005
Posts: 1,126
Likes: 0
From: Hudson Falls, N.Y. 76 Vette Modified L-48
Originally Posted by 77fromHeaven
.....Also the car sat for a month, while I was waiting to install the new MC....
Le Mans Master
Joined: Jul 2004
Posts: 6,248
Likes: 4
From: Lancaster PA
I don't know what you did with your old one but don't give it back as part of your core charge. The new replacement I got wasn't the same as the original. I went to the junk yard and got a master cylinder to return and kept my original MC in case I want to rebuild and return to original.
Racer
Joined: Jul 2002
Posts: 254
Likes: 0
From: Crofton MD
Leaking MC
A leaking MC means that the brake fluid is getting past the plunger, not that fluid is leaking out of the body. You can not build up pressure is the fluid gets aroung the seal. For my 77, I went to the local Auto Parts and picked up a rebuilt MC. It turned out to be indentical to the one in the car. It came with little plastic plugs for bench bleeding which is very simple. When I put the rebuilt one in and connected the lines, I checked the pedal and it was firm. I drove the car and it seemed fine so I did not bleed the lines. It wasn't until about a year later that I bleed the brakes when I flushed the lines. Probably not the recommended procedure, but it worked for me
