Master cylinder replacement

GEARS

2005 140WB standard roof
Greetings :cheers:

I need to replace the master cylinder on my 2005 316 Sprinter.

Anyone have any suggestions or tricks of the trade?

Jon
 

GEARS

2005 140WB standard roof
Why do you believe you need to replace it? Doktor A
Hi Doktor :cheers:

If I push on the brake pedal and hold it, the pedal will eventually sink to the floor.

On a side note the reservoir appears to be filled with some crazy thick brake fluid...:wtf:
 

ZED

Sprinter Newbie
That means the fluid is contaminated with water. It will get dark. In extreme cases it will get thick. COMPLETELY flush the brake system and you will likely be back in business.
 

abittenbinder

Doktor A (864-623-9110)
Hi Doktor :cheers:

If I push on the brake pedal and hold it, the pedal will eventually sink to the floor.

On a side note the reservoir appears to be filled with some crazy thick brake fluid...:wtf:
Try this first, here's a reprint of my spring '08 posting that may be helpful:

"I receive a lot of mail and phone calls on the subject of ('02-'06)
Sprinter brake pedal feel, especially a perceived "abnormal sinking
pedal".

Many first time Sprinter owners or those who drive other vehicles
(more often than their Sprinters) are alarmed by a brake pedal feel
that they are convinced is abnormal.

Here's how to tell if your Sprinter brake pedal action is "normal" OR
in need of immediate service attention:

Engine running, push lightly on the brake pedal. Mushy and sinking
seemingly endlessly toward floor? This may be NORMAL.

Engage Park and handbrake. Shut off the engine and then step on brake
pedal 4 or 5 times. This releases the vacuum from the booster servo
and reservoir-you should hear a loud hiss when pressing pedal each
time until the vacuum is expended.

Engine still OFF, ALL vacuum expended, now step on brake pedal and
exert a steady force. Pedal should move a relatively short distance
(compared to before) and stop hard without further sinking- REGARDLESS
of how long you exert foot pressure. This is the TRUE test of the
brake master cylinder. If pedal slowly sinks to floor during this
test- you have a problem.

Now step on pedal again and exert steady pressure while starting
engine. With engine now running- the pedal should begin sinking
steadily toward floor. This is NORMAL and indicates the engine's
vacuum pump and the brake servo are working properly.

Take foot off the brake pedal and run the engine for a few seconds at
1500 rpm to build vacuum. Go back to idle speed, step on the brake
pedal slowly-see the difference and the much greater sink distance
compared to engine "off" and vacuum released?

Still convinced it's excessive pedal travel? Try this test-Engine
running, move Sprinter to a downward sloping driveway, place in
neutral and SLOWLY creep down hill. Gently apply brake pedal pressure
and note how little pedal travel is needed to stop and hold the
vehicle-now push harder-see how much pedal travel remains?

This long, soft, pedal travel is a normal characteristic of the
Sprinters vacuum booster design when engine is running." Doktor A
 

GEARS

2005 140WB standard roof
That means the fluid is contaminated with water. It will get dark. In extreme cases it will get thick. COMPLETELY flush the brake system and you will likely be back in business.
Actually the fluid is clear, looks like water but flows like honey.
 

220629

Well-known member
Gears,
So all you heard was the chirping of crickets?

Were I you the first thing I would do is suck out the master cylinder and refill with the proper fluid. I believe that is DOT 4+, but verify that because my memory is somewhat lacking. If you were more motivated than I am, I suppose the better thing to do would be to MT the master cylinder, refill with proper fluid and then flush through the wheel cylinders to get all the old stuff out. Keep in mind that even doing that method of flush doesn't flush some of the anti-lock brake fluid components which need to be operated by a DRBIII dealer computer interface tool.

Based upon your comments to date, I wouldn't replace the master cylinder yet unless it seems stopping is a safety issue. Hope this does some good. AP/vic
 

DGMorrisSF

New member
Not sure if this thread is still active but I am having intermittent brake problems on a hill where the brakes work and then unexpectedly fail in that the pedal goes close to the floor and the vehicle starts to drift. I am able to stop with full pedal or engaging the parking brake. I suspect the master cylinder. Any other thoughts before I undertake the replacement? Other than this symptom is there anything else I should test? Fluid is fine. No obvious leaks.
 

lindenengineering

Well-known member
Well here' s some tips from the trade and being trade there will be some that disagree with these tips.
That stated first buy NEW M/Cylinder either factory or something like Napa's premium product .
Remove the reservoir from the existing M/cylinder , drain it and fit it to the doner.
Lightly mount the donor in a vice and fill the reservoir with NEW fluid DOT4 plus 1 (MB fluid) .

Since the M'cyl is provided with plastic blank plugs remove the plug furthest away from the plunger .
Pump the dry master cylinder with a suitable rod, like a big Philips screwdriver until it squirts fluid out of that delivery port .
Now plug the port with your finger and pump the plunger some more until fluid squirts out the the back port
.Now plug the ports with the plastic plugs provided to prevent fluid from escaping.

Remove your old m/cylinder and install the new one ensuring the servo rod engages with the plunger and that the O ring sealing the master cylinder to the the servo casing is replaced (read important)
Connect the bundy pipes up, but leave them 1 turn loose.

With an assistant have he or she slowly depress the brake pedal as fluid squirts out of loose sleeve nuts , then snug them up BEFORE releasing the pedal .
At this stage the brake should have some "feel" to it and then pump up the brake ,then open in turn after each pump, the lose bundy pipe nut bleeding any remnants of air out of the master cylinder and before it gets introduced into the ABS brick.
Now leave it for a few hours and any small air bubbles will propagate up and self vent through the M/Cyl and reservoir.

Get this technique "right" and shouldn't need to bleed the entire system
Dennis
 
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DGMorrisSF

New member
THANK YOU DICK AND DENNIS. YOU'RE BOTH AMAZING!!! I'll let you know how it goes.. My Sprinter is a 2004 2500



What year Sprinter?

The brakes are covered in both the service manuals and possibly in the Body or Chassis manuals.
For various years, they're available at http://diysprinter.co.uk/reference/
For example, the 2006 manual is http://diysprinter.co.uk/reference/2006-VA-SM.pdf
The 2003 manuals are in http://www.diysprinter.co.uk/reference/2003SprinterManuals.zip

--dick
Well here' s some tips from the trade and being trade there will be some that disagree with these tips.
That stated first buy NEW M/Cylinder either factory or something like Napa's premium product .
Remove the reservoir from the existing M/cylinder , drain it and fit it to the doner.
Lightly mount the donor in a vice and fill the reservoir with NEW fluid DOT4 plus 1 (MB fluid) .

Since the M'cyl is provided with plastic blank plugs remove the plug furthest away from the plunger .
Pump the dry master cylinder with a suitable rod, like a big Philips screwdriver until it squirts fluid out of that delivery port .
Now plug the port with your finger and pump the plunger some more until fluid squirts out the the back port
.Now plug the ports with the plastic plugs provided to prevent fluid from escaping.

Remove your old m/cylinder and install the new one ensuring the servo rod engages with the plunger and that the O ring sealing the master cylinder to the the servo casing is replaced (read important)
Connect the bundy pipes up, but leave them 1 turn loose.

With an assistant have he or she slowly depress the brake pedal as fluid squirts out of loose sleeve nuts , then snug them up BEFORE releasing the pedal .
At this stage the brake should have some "feel" to it and then pump up the brake ,then open in turn after each pump, the osse bundy pipe nut bleeding any remnants of air out of the master cylinder and before it gets introduced into the ABS brick.

Get this technique "right" and shouldn't need to bleed the entire system
Dennis
 

lindenengineering

Well-known member
Brought to you from a Citroen dealership technique where I did my exchange student apprenticeship so many moons ago (1971) in France
Dalle Frères, Citroen Renault concessionnaires, Rue de Billemont, Roncq Nord 59.
La Belle France.:thumbup:
Dennis
 

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