how do you bench bleed a mc???

[dentmasters01]

I'm switching over to manual brakes and I've tried 3 different mc, including a new reman from autozone and this is what I get. I've got the mc on my work bench and I've got small brake lines running over into two cans of brake fluid. I fill up the mc and start pumping the plunger. the rear port (closest to the firewall) fills the can up. The front port (going to rear brakes) the level doesn't change??? Both mc's from the jkyd did this so i got the reman'd one and the same thing happens. what is going on?? am I missing something?

 

[Preston87GN]

well im not sure if this will work for you but when I put in a vacuum assisted brake Master Cylinder I put it in a vise and hold it genlty.then I plug off the line holes of the mc and fill the resevoir and then pump the plunger until it gets hard to push.

 

[BlackMetal]

I'm curious too, I've been reading your threads about having problems getting these junkyard MCs to bleed but it sounds like you are doing it right, not sure what the problem is.

 

[Nick Micale]

well im not sure if this will work for you but when I put in a vacuum assisted brake Master Cylinder I put it in a vise and hold it genlty.then I plug off the line holes of the mc and fill the resevoir and then pump the plunger until it gets hard to push.

This is the correct answer.

However, how this is done is important. My procedure is to slowly push the plunger in [with a screwdriver or ?] until it stops, hold it a few seconds and release. WAIT at least 30 seconds before pushing again. This may take 5 or 20 pumps?

Once this is done and the piston will move only 1/4-1/2", you are ready to install the MC.

If you are only changing the MC and have not disturbed the brake lines or wheel cylinders, you can do the install w/o having to bleed the brakes - assuming you had a good pedal to start.

First, bolt up the MC with the plastic plugs still installed in the ports. Remove the plus one at a time and screw in the line immediately after removing the plug. LEAVE THE LINE NUT HAND TIGHT ONLY.

You can have a rag under the lines to catch the fluid dripping out. After about 5 minutes, tighten the nuts with a wrench. MAKE SURE PLENTY OF FLUID IS IN THE RESERVOIR.

Have your "assistant" [usually your wife or kid!] get in the seat. Have her [or him] push the pedal and NOT release it until you give the word. Then open each line nut until fluid is released. It may be necessary to do this twice if air is also expelled with the fluid.

I have used this procedure for many years and it has always worked for MC changed or when converting from PM to vac.

A common problem when changing a MC is NOT bleeding it properly, or completely before install. It then will PUSH air into the lines and make a big problem for the less experienced.

Hope this make your job easier.

 

[dentmasters01]

ok, if the above procedure is correct, how does the air excape the mc if you "plug off" the ports and just pump the cylinder? the ports are where the air is supposed to be expelled. All other procedures I read last night on line said to run two tubes from the ports over into the reserv. and pump it that way or into another cup or can with the tubes submerged in brake fluid.

 

[Nick Micale]

Why do I even spend time typing [with 2 fingers!] try to help with a procedure that I have done for over 30 years and get a reply, "how does it work".

Does it matter how the hell it works?

Go check with your local parts counter "expert" and ask him for help and "how it works".

 

[dentmasters01]

ok, so when you first got into cars and wanted to know how something works did you ask question or did a little chinese man magically apear and tell you certain things??? I just wanted to know how things work, is that too much to ask?? If you don't want to help, or want to go to the trouble of explaining things you know about and how they work then don't respond !! Someone else will help out those of us who want to learn more about "how things work" compaired to "just do this" and wonder why you do it. I was asking because EVERY ARTICLE I READ LAST NIGHT WAS DIFFERENT THAN WHAT YOU TOLD ME ! thanks for being a d!ck in your response. Its no wonder the buick world is so united and friendly

 

[Preston87GN]

well to add to your question were does the air go...it will go to the only place left it can go and thats in the reservoir.As you pump the plunger back and forth it pulls fluid in then pushes the air into the reservoir.I hope you get it working

 

[Nick Micale]

ok, so when you first got into cars and wanted to know how something works did you ask question or did a little chinese man magically apear and tell you certain things??? I just wanted to know how things work, is that too much to ask?? If you don't want to help, or want to go to the trouble of explaining things you know about and how they work then don't respond !! Someone else will help out those of us who want to learn more about "how things work" compaired to "just do this" and wonder why you do it. I was asking because EVERY ARTICLE I READ LAST NIGHT WAS DIFFERENT THAN WHAT YOU TOLD ME ! thanks for being a d!ck in your response. Its no wonder the buick world is so united and friendly

You ask a question, I answer it in DETAIL, and you call me a "dick"? Typical punk response. Your lack of knowledge is only exceeded by your lack of mechanical ability, or maybe reading skills?

Your attitude is exactally why many qualified and experienced people very seldom or never post because some "kid" has to question their abilities. I am also very well aware that there can be more than one method or procedure to solve a problem, not just a right or wrong way.

No I did not have a "magic chinese man tell me certain things", I watched, listened and skinned lots of knuckles to learn my trade, probably before you were born.

Computers, TV's, remote controls and other "tech advances" have left a big generation gap? I wonder where you are going to find skilled craftsmen when we are gone? I am not a part of the "instant gratification" generation.

Maybe if you had a little more patience and understanding you could have figured out, like someone else did, that the fluid replaces the air?

 

[dvernst]

Chill out! just because your way works, or is the right way how is he going to learn if he doesnt understand why it works that way. Maybe he wanted to ask more before he got back to his garage? Seems like a simple harmless question to me. It sure doesnt seem like he's questioning your knowlege or ability. Like he said. If his response bothers you. DON'T ANSWER!!!!!

 

[dentmasters01]

You ask a question, I answer it in DETAIL, and you call me a "dick"? Typical punk response. Your lack of knowledge is only exceeded by your lack of mechanical ability, or maybe reading skills?

Your attitude is exactally why many qualified and experienced people very seldom or never post because some "kid" has to question their abilities. I am also very well aware that there can be more than one method or procedure to solve a problem, not just a right or wrong way.

No I did not have a "magic chinese man tell me certain things", I watched, listened and skinned lots of knuckles to learn my trade, probably before you were born.

Computers, TV's, remote controls and other "tech advances" have left a big generation gap? I wonder where you are going to find skilled craftsmen when we are gone? I am not a part of the "instant gratification" generation.

Maybe if you had a little more patience and understanding you could have figured out, like someone else did, that the fluid replaces the air?

ok, first of all just for the record you didn't asnwer my question. May be YOU need to learn to read. I labeled the thread with a "general" question and then I asked about a "specific" problem during the bleeding procedure in the first post. no fluid was coming out of the 2nd port during bleeding. Please go back and read the first post to refresh your memory. You answered in detail but said Nothing that would lead anyone to a diagnosis of what was happening with my mc. Matter of fact, if we use your procedure, and plug up the ports, how do you know if there is something wrong with one of the two pistons inside the mc ???? The plunger will still go back and forth, but how do you know its not just pushing one of the two pistons instead of both??? And if you plug the ports, the piston reaches the "compression" and just where does the air have to go??? OUT THE PORT. If your method works, then why not just bolt it to the car, attach the lines and pump it a few times?? both are a "closed" system and should work the same.....but it doesn't. here's a good diagram of a mc if you didn't already know with all your great knowledge. once the piston goes past the fluid intake and return port there is no where else the air can go except out the port? and when you release the pressure, how do you know the trapped air would flow out the fluid intake? still didn't tell me why no fluid was coming out the port....PART 5 - How the Master Cylinder works

I never questioned your "abilities", I only wanted to know HOW it worked. I'm sure your a great engine builder, I wanted to know "how", if you close off the only way for air to get out of a pressurized system, it could be "blead" ? lets reread the post's....YOUR attitude came out and tried to belittle me for asking "why" FIRST. As far as you assuming you know me by the punk and kid remarks........ nothing has been Instant gratification as you put it. I moved 700 miles away from my family at age 25 to start my own business. I'm 36 now, and make over 100k a year because I get up and pour blood and sweat into it to make it work...as I assume you do as well, You may be older than me but what the hell does that prove?? Wheels were once made of wood too, that doesn't mean they are better.

all I wanted to know is "how" it worked.....
sorry if this has gotten out of hand.

 

[BlackMetal]

You ask a question, I answer it in DETAIL, and you call me a "dick"? Typical punk response. Your lack of knowledge is only exceeded by your lack of mechanical ability, or maybe reading skills?

Your attitude is exactally why many qualified and experienced people very seldom or never post because some "kid" has to question their abilities. I am also very well aware that there can be more than one method or procedure to solve a problem, not just a right or wrong way.

No I did not have a "magic chinese man tell me certain things", I watched, listened and skinned lots of knuckles to learn my trade, probably before you were born.

Computers, TV's, remote controls and other "tech advances" have left a big generation gap? I wonder where you are going to find skilled craftsmen when we are gone? I am not a part of the "instant gratification" generation.

Maybe if you had a little more patience and understanding you could have figured out, like someone else did, that the fluid replaces the air?

You are completely out of line here, he didn't question your abilities, you told him HOW to fix the problem and he simply wanted to increase his own personal knowledge by asking WHY that method would solve the problem, because he didn't understand it. There is nothing wrong with that. Many people do not learn just from being told what to do, they want to understand the process and theory behind it.

If answering questions as a favor to someone with less knowledge is such a hassle to you, then why the hell come to a message forum and offer to answer questions? Go sit in a corner somewhere and stroke your ego, knowing that you're the last generation of "skilled craftsmen".

Maybe if YOU had a little more patience and understanding, you wouldn't puff out your chest and act like a moron just because someone asks a follow-up question. We are all here to help each other out and nobody else has an attitude like that "I just did you a favor, don't question me". Like I said, log off and don't share your vast knowledge with us anymore, if it's such a pain in your ass.

 

[turbo87regal]

Derek, Just take lines you have hooked up to the ports on the side and loop them back into the reservoir and fill it with fluid and make sure the lines are submerged in the fluid then pump the master slowly until you get as much air out of it as possible and once you install it bleed the whole car because you never get all the air out of the system by bench bleeding.


As far as the procedure Preston87GN posted goes
I've been ASE certified and doing brakes for a living for 14 years now and never heard of pluging off the ports to bleed a master cylinder I guess you learn something new everyday but I will stick to the standard method

You can also use the method Nick Micale posted witch I dont think was the one you were questioning in the first place so I dont know why he got all bent out of shape Its just a little more complicated and easier to screw up for someone that has never done it before.

 

[dentmasters01]

I bled the mc on the bench with the loop method. I installed it on the car and I've bled the lines till my leg is tired .....pedel still fills mushy. I was hoping to get better back brakes out of this. the car is still on stands and as soon as I push the on the gas with the brakes held as tight as possible the rears just start spinning. I'm borrowing a buddies pressure bleeding system tomorrow and I'll try that.

 

[Preston87GN]

well turbo Ive been at it for 20 years...I just installed a MC Friday doing it the way I posted and it worked fine. I just posted to try and help out and yes a good mechanic/technician will always learn something new(and 14 years I would say you have learned a few things)....goodluck dentmaster I told you what I can.

 

[dentmasters01]

well turbo Ive been at it for 20 years...I just installed a MC Friday doing it the way I posted and it worked fine. I just posted to try and help out and yes a good mechanic/technician will always learn something new(and 14 years I would say you have learned a few things)....goodluck dentmaster I told you what I can.

no prob. I appreciate your responses.