W123 brake Master Cylinder shot or not?. (Pictures) - Page 2 - PeachParts Mercedes-Benz Forum

leathermang · #16 03-04-2010, 09:58 AM

IF a master cylinder needs to be bench bled... it needs to be bench bled... then when on the car the power bleeder can be used in conjunction with bleeding the rest of the system...
The bench bleeding kit with multiple size fittings to fit most any MC can be found at Napa and lots of other auto parts stores... there are several good threads in the archives about this stuff..
Don't wind up having to take off the MC because you thought it could be bled in the car if the instructions call for it being bench bled... I have tried that... that extra time to take it back off the car and do it correctly is time you will never get back. And you will feel foolish all during that time...

Diesel911 · #17 03-05-2010, 08:47 PM

The last 2 rebuilt Master Cylinders I bought came with the Bench Bleeding Kit already in the box from the rebuilder.
You could just check inside of the box before you leave the store to see if it is in there.

leathermang · #18 03-06-2010, 01:19 AM

That would have totally saved me a trip to Austin and stopping at four auto parts houses..

tfernandez · #19 03-06-2010, 03:44 AM

a friend and myself replaced my master cylinder not but 4 days ago. for the bench bleeding process we just used our fingers to plug the holes. it's a little tough by yourself though, but i wouldn't rush out and buy a bleeding kit if the MS doesn't come with one.

t walgamuth · #20 03-06-2010, 05:11 AM

I tried to bench bleed a mc once and wound up with brake fluid dripping from my ceiling.

Now I just put it on and crack the brake lines and bleed them one by one.

toomany MBZ · #21 03-06-2010, 08:42 AM

Quote:

Originally Posted by leathermang

IF a master cylinder needs to be bench bled... it needs to be bench bled... then when on the car the power bleeder can be used in conjunction with bleeding the rest of the system...
The bench bleeding kit with multiple size fittings to fit most any MC can be found at Napa and lots of other auto parts stores... there are several good threads in the archives about this stuff..
Don't wind up having to take off the MC because you thought it could be bled in the car if the instructions call for it being bench bled... I have tried that... that extra time to take it back off the car and do it correctly is time you will never get back. And you will feel foolish all during that time...

I agree, if it (master cylinder) needs to be bled, bleed it.
Yet with two people it can be bled in car, same procedure as caliper bleeding and while you have a helper, do the entire system.

vwnate1 · #22 03-06-2010, 10:40 AM

Master cylinders never ' need ' bench bleeding , it's a time saving device for flat rate dealer or high production Mechanics .

The entire system requires bleeding every time you open it , yes I know how to change a caliper etc. and only bleed that part of the circuit , that's wrong and short cutting the job , I don't work that way .

Bench bleeders are easy to make : go to any junkyard and look for a smasher , carry your flare nut wrenches to suit the car you're working on & when you find one with the same size fittings , cut them off leaving 12" or so of pipe , unscrew them and take home , bend in a more or less 'C' shape so when you screw them into the new master cylinder they dump back into the resivoir and have at it .

Remember to only support the master cylinder by clamping the flange . never,
EVER anywhere else as you'll distort the bore , even of a cast iron cylinder .

Lastly , I feel that rebuilt master cylinders are Penny Wise And Dollar Foolish as you didn't do the rebuilding and most ' rebuilders hire minimum wage earners and teach each one to do one specific part of the job , this is poor practice .

lietuviai · #23 03-06-2010, 11:44 AM

Looks like I have the same problem Fred, the thread starter has. The paint on the booster is gone too. Mine's been this way since I bought and resurrected my car. It's been that way for at least two years or so but I haven't experienced any braking issues. I've only had to add a little brake fluid in that time once. I sort of wonder if it was fixed by the PO sometime back since I've never seen any dampness on either the MC or the booster.

Diesel911 · #24 03-06-2010, 12:06 PM

Quote:

Originally Posted by toomany MBZ

I agree, if it (master cylinder) needs to be bled, bleed it.
Yet with two people it can be bled in car, same procedure as caliper bleeding and while you have a helper, do the entire system.

Yep, that is what I do. I do not use the supplied tube kit. I just put some rags under the Master Cylinder Outlets that have the Brake Line screwed in loosely (like bleeding the air frim Injectors).
My Wife pushes on the Brake Pedal and holds it while I tighten the Line Connectors. She releases the Brake; afterwhich I loosen the Line Connectors. She pushes and holds the Brake Pedal again and I repeat the above until the air is out of the Master Cylinder.
If you are careful doing that you normally do not need to bleed the complete system.
However, a test drive will quickly tell you if you have Air in your system and it needs further bleeding.

Diesel911 · #25 03-06-2010, 12:14 PM

Quote:

Originally Posted by vwnate1

Master cylinders never ' need ' bench bleeding , it's a time saving device for flat rate dealer or high production Mechanics .

The entire system requires bleeding every time you open it , yes I know how to change a caliper etc. and only bleed that part of the circuit , that's wrong and short cutting the job , I don't work that way .

Bench bleeders are easy to make : go to any junkyard and look for a smasher , carry your flare nut wrenches to suit the car you're working on & when you find one with the same size fittings , cut them off leaving 12" or so of pipe , unscrew them and take home , bend in a more or less 'C' shape so when you screw them into the new master cylinder they dump back into the resivoir and have at it .

Remember to only support the master cylinder by clamping the flange . never,
EVER anywhere else as you'll distort the bore , even of a cast iron cylinder .

Lastly , I feel that rebuilt master cylinders are Penny Wise And Dollar Foolish as you didn't do the rebuilding and most ' rebuilders hire minimum wage earners and teach each one to do one specific part of the job , this is poor practice .

One of the ways to grip tender parts in a Vice is to use Wood between the Vice Jaws and the parts. That would be good enough to grip a Master Cylinder for Bench Bleeding.

For tighter grips get or make sone Aluminum or Copper jaw covers for your Vice (for those who do not like Vice marks on their Injectors when they rebuild them).

leathermang · #26 03-06-2010, 12:57 PM

LOL, some of you are youngsters at mechanicing who have not had a chance to experience the variety of different situations for which your proposed absolute and blanket statements would prove unsuitable and ineffective.... and sometimes dangerous.

I am sure those instructions citing the need for bench bleeding were just an effort to sell the bleeding kits or harass the DIY mechanic.
And I am not even a conspiracy theorist....

Diesel911 · #27 03-06-2010, 04:03 PM

At 58 years old I do not know if I qualify as a youngster. But, if something does not work for me I stop doing that and go on to something else.

If I say this is the way I do something; it is up to the person reading the comments to decide if they want to try that or not.

As an example some members have said they have peened the rivets on their replacement Timing Chains with a Ball Peen Hammer and something heavy on the otheside of the Chain to back it up.
The did it and it evidently worked for them. But, after reading that I decided it is beyond my level of risk taking, luck and even skill to pull something like that off unless there was no other choice. So that is advice I am not going to take.

As far as the Master Cylinder Bleeding kits Go; my Father never had one (I used to push the Pedal for him) and I never did either untill one came Free in the box with a Rebuilt Mastercylinder. In between the times of helping my Father and getting the Free Mastercylinder Bench Bleeding Kit I had long gotton used to doing the job without one.

None of the above is a recommendation not to use a Master Cylinder Bench Bleeding Kit.

vwnate1 · #28 03-07-2010, 01:29 AM

Quote:

Originally Posted by leathermang

LOL, some of you are youngsters at mechanicing who have not had a chance to experience the variety of different situations for which your proposed absolute and blanket statements would prove unsuitable and ineffective.... and sometimes dangerous.

I am sure those instructions citing the need for bench bleeding were just an effort to sell the bleeding kits or harass the DIY mechanic.
And I am not even a conspiracy theorist....

I hope you weren't referring to [I][U]me[U][I] there.....

Diesel911 · #29 03-07-2010, 12:54 PM

Back in the past commonly rebuilt parts came with no instructions in the Box at all unless there was some special installation proceedure and people often installed them without having or reading any repair manual.

My Father had some advantage as after WW2 he used his GI Bill to go to Trade School to be a Mechanic. Only to find that he did not like it and never worked as a Mechanic.

He in fact never liked working on his own Cars but did it because he knew how and to save money and to not get cheated by the Real Mechanics.

leathermang · #30 03-07-2010, 03:54 PM

Diesel911, I HEAR THAT !!!!!!! I only LIKE to work on small engines that I can pick up by hand and move around in the shop...