Brake Master Cylinder - Replace and bleed method

[mtriple]

Greetings everyone,

So my Brake MC is shot.  I already ordered a new one along with the plastic elbows from reservoir.  I plan to tackle this along with my son who will be the brake pedal pusher in this case.

I looked everywhere and most of the posts here talk about replacing the entire system and no specific steps regarding the MC actual in car bleeding simple method (dare I say)?

 

Here is what I intend to do.  my current setup is a tii booster with standard MC (to clear the Vstacks) please feel free to correct me.

1) Cover area underneath with towels and protect paint..etc.

2) Remove the reservoir hoses from MC and block them somehow while I am replacing the elbows.  Perhapd lift the 2 hoses up and clamp them? 

3) Unscrew the brake lines from the MC 

4) Disconnect the MC from Booster and inspect/remove any brake fluid from booster and dry with brake cleaner. 

5) Attach but not tighten all brake lines to booster

6) Screw the MC back onto booster (align pushrod inside of course prior)

7) Plug back 2 reservoir lines to top of MC

 

Here is what I am not 100% clear : The bleeding part.  What I gather is while the brake lines not fully screwed in to MC, I push the brake pedal and keep it down firmly, THEN tighten the 5 lines into the MC followed by releasing the brake pedal.  Afterwards, I loosen the brake lines, then push the brake pedal, keep down, then tighten the lines and release the brake pedal.. I am under the impression that I need to do this 5 - 7 times maybe?

1) Is this method correct and 2) does the bleeding process need to involve all 5 brake lines loosen/tighten or specific ones would be suffecient? if so which ones?

 

I must mention that I had a full brake flush at the shop last year and there is no visible loss of fluid or leaks at any caliper.

 

Sorry about the long post.  I just think its a good little project to do with my son over the weekend.  I appreciate all the help!

 

Thanks

Hamada 

[2002iii]

I like to use an old turkey baster to suck up most of the brake fluid out of the reservoir.

 

After you install the new master cylinder you just fill the reservoir with fluid and bleed the brakes as normal from the caliper bleeder screws.

 

I've never heard of this method:

45 minutes ago, mtriple said:

The bleeding part.  What I gather is while the brake lines not fully screwed in to MC, I push the brake pedal and keep it down firmly, THEN tighten the 5 lines into the MC followed by releasing the brake pedal.  Afterwards, I loosen the brake lines, then push the brake pedal, keep down, then tighten the lines and release the brake pedal.. I am under the impression that I need to do this 5 - 7 times maybe?

1) Is this method correct and 2) does the bleeding process need to involve all 5 brake lines loosen/tighten or specific ones would be suffecient? if so which ones?

 Sound like you would spray brake fluid all over the engine bay.

[Leucadian]

Seconded, seems a bit complicated.

 

If you are planning on removing the brake fluid from the reservoir, and replacing with new, you'll need to bleed the slave cylinder, as well as the brakes.  If not, just make sure the brake fluid level doesn't fall below the clutch line inlet. 

 

Good luck!  

[Hans]

You need to bleed the whole system. Do you have the correct order? How old are brake hoses?

May be a bit late, but it may be easier to replace hoses from res to cyl in order to get elbows installed.

Edited March 15 by Hans

[mtriple]

Thank you all for chiming in.  Will bleed the whole system then.  Hans, the SS brake lines are just a few years old.  they're in good shape.

 

have a great weekend!

[mtriple]

2 hours ago, Hans said:

You need to bleed the whole system. Do you have the correct order? How old are brake hoses?

May be a bit late, but it may be easier to replace hoses from res to cyl in order to get elbows installed.

where can I pickup the hose from res to MC? is it online only?

[HobieDog]

22 hours ago, Leucadian said:

Seconded, seems a bit complicated.

 

If you are planning on removing the brake fluid from the reservoir, and replacing with new, you'll need to bleed the slave cylinder, as well as the brakes.  If not, just make sure the brake fluid level doesn't fall below the clutch line inlet. 

 

Good luck!  

Not sure the slave would need to be bled if clutch isn’t touched during the process.  I’m replacing my reservoir in a week or so and wasn’t planning on it…just sucking out the fluid from reservoir, clamping the line and putting in a new reservoir, then reconnecting.  Air bubbles won’t travel down the line and if the clutch isn’t depressed it should be good…right?  
 

Maybe a few taps on the line after it’s all connected to help move fluid into the line if some spilled out.  
 

happy to be wrong, that’s my thought process. 

[Son of Marty]

If your wife won't let you use the turkey baster to suck the reservoir dry (their funny that way) take a bit of plastic wrap and  place it under the cap to slow leakage then when you get the feed hoses off use a small container to drain the fluid when you open the cap. Yeah if you don't touch the clutch there's no need to bleed the clutch unless you want to.

 

PS. your going to spill some brake fluid anyway you do it so be ready with some rags.

Edited March 15 by Son of Marty

[2002iii]

1 minute ago, Son of Marty said:

If your wife won't let you use the turkey baster to suck the reservoir dry (their funny that way) take a bit of plastic wrap and  place it under the cap to slow leakage then when you get the feed hoses off use a small container to drain the fluid when you open the cap. Yeah if you don't touch the clutch there's no need to bleed the clutch unless you want to.

Notice I said old turkey baster. I wouldn't want to eat any turkey that has been basted with brake fluid!

[Son of Marty]

That's silly, just clean it with some brake clean😄.

[tzei]

Why loose exciting dressing?

[Hans]

6 hours ago, mtriple said:

where can I pickup the hose from res to MC? is it online only?

Google Continental brake hose. Maybe big box auto stores. Dealer in a pinch. Easier to put elbows in new hose, wiggle elbows into master, attach hose to res. Put some brake fluid in hose end.

[tech71]

8 hours ago, mtriple said:

where can I pickup the hose from res to MC? is it online only?

You can probably  a chunk of hose that will work at an auto parts store.

If you want the OE lookin fabric cover stuff may have to go online like here:

OEM Brake Hose - BelMetric

BELMETRIC.COM

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Bel-Metric sells metric hardware & specialty automotive supplies nationwide. Visit our website to purchase metric fasteners, nuts, bolts, Time-Sert kits & more.

 

[tech71]

On 3/14/2024 at 11:38 AM, mtriple said:

Here is what I am not 100% clear : The bleeding part.  What I gather is while the brake lines not fully screwed in to MC, I push the brake pedal and keep it down firmly, THEN tighten the 5 lines into the MC followed by releasing the brake pedal.  Afterwards, I loosen the brake lines, then push the brake pedal, keep down, then tighten the lines and release the brake pedal..

I dont think thats really necessary and seems a bit over complex , I get the concept and employ a similar process sometimes on brake calipers mainly because I am usually working solo. But you have a dedicated pedal pumper, there's no need.

I would fully install the MC and just bleed the brakes., clutch too, why not? Just keep the MC topped up.

Start at  passenger rear, bleed through the ports, push all the old fluid out even if it is only a year old. Brake fluid absorbs moisture, moisture reduces the boiling point of the fluid quite a bit, makes rust too. BMW recommends replacing brake fluid yearly.

 

Edited March 16 by tech71

[Son of Marty]

Or you could spend 50 bucks and get one of these baby's.