Mercedes Sprinter master cylinder removal...

[gerrymoore]

Campervan failed MOT on brakes and the master cylinder is faulty as pedal, under pressure, goes slowly right down to the floor. It's not ABS so should (I thought) be an easy fix...not! Van is 2003 and I cannot budge the brake pipe nuts. I've tried WD40 and will leave overnight but last thing I want to do is damage the brake pipes!! As I'm putting a new cylinder on, would I be OK trying some heat from a blowlamp to loosen the brake pipes?? Anyone any bright ideas? Thanks Gerry

 

[dobbslc]

A hot air gun might be safer, have you got a proper spanner?

 

[Wildefalcon]

Freeze spray on the MC. Followed by gentle heat on the nut. And plusgas the night before.

 

[bricol]

Proper flare nut spanners help to void rounding off the tube nuts.

I'd be warming the cylinder and freezing the tube nut - trying not to set the whole thing on fire as brake fluid does burn rather well. - in an attempt to expand the cylinder away from the cooled nut. Tightening them first and wriggling back and forward.

However, if the nut is rusted seized in the cylinder, and it uses steel pipes, don't be surprised when the tube simply twists up in a nice decorative spiral as you undo the nut . . .

 

[gerrymoore]

No havent got the proper spanner...but i can buy one ... i have got a heat gun but no freeze spray or plus gas... but i can buy some .... anything to avoid damaging 18 year old brake pipes thanks for info guys ... long time since I did this sort of job ( 1967 mark one escort I think) ....God I am old

 

[johnik]

use the proper spanner or you wil round off your nuts

 

[rtcosic]

... I've tried WD40 and will leave overnight but last thing I want to do is damage the brake pipes!! ...

Using a release agent or penetrating fluid like PlusGas will be much more effective than using a Water Dispersant.

Treat yourself to the proper spanners - you will appreciate it!

 

[gerrymoore]

Ok .... halfrauds have the spanner and screwfix have the freeze/penetrating stuff ... ill get these tomorrow and attack with much gusto, the heat gun, and freeze spray .... watch this space

 

[The_Yellow_Ardvark]

They are a real pain.

Crack a bleed nipple on each corner, this takes out any residue pressure. Should not be any, but I have had it.

Wrap a towel round the master cylinder and pour 4 kettles worth or boiling water over the body, avoiding getting any into fluid.

Get a pipe brake spanner, double check the size, my duff memory tells me they are 11mm or 12mm.

First tighten then up a wee bit. You are looking for a movement in the fitting, not to much. Just a hint that they are shifting.
Then undo them. If they start to bind tighten up and rock back. Brake fluid at this stage will help to lubricate the thread.

Learn and use a few cuss words.

Lower down you will see the brake pipe clips.
Hope they are not riveted on, undo them and that will allow the pipes to moved out of the way.

The 2 nuts holding the cylinder on should be 13mm, 6 sided socket.
Should be.

Oh yes, pop out the vaccum pipe as well.

Remove and refit the new one.
Refitt pipes, bleed the master and then bleed the brakes.

I will not help you.
It is a pain.

The 8mm bleed nipples will be tight.

 

[Matchless]

on my last sprinter the master held the brakes on, I had to grind the operating rod inside the servo down a bit, when I bought it the brakes had beeen on fire, I replaced the callipers, pads, discs and hoses but the master was new, took 10 thou off the rod and all was well!

 

[roofman]

Crack the bleed nipple and plenty of localized heat right on the pipe nut (MAP gas is best)..forget sprays as useless they are.

 

[Barking Mat]

Brake pipe spanners...

Life savers.

 

[piman]

He;llo Gerrymoore,

I wouldn't have ythou8ght it's too big a job to replace the brake lines anyway? Maybe lesss of a job than trying to undo the nuts without damaging the lines?

Alec

 

[arther dailey]

is there enough spare length in the pipes to cut them off at the back of the nut , put new nut on reflare and refit ? when trying to undo the nut watch the pipe for twisting with the nut ..

 

[gerrymoore]

I've just got the flare spanner and freeze spray but 'going out' for lunch today with family for 1st time in a year so brakes can wait 'til tomorrow!! Good idea of Arthurs (assuming you can buy new nuts) as I have a flaring kit. A lot of stuff is out of stock...the MOT noticed a caliper bolt missing (arrggghhh) but when I rang Mercedes they are 'not available' at the moment??

 

[CompoSimmonite]

When unions are that bad I expect to replace brake pipes as well.

 

[KTMart]

I had a 2000 reg sprinter and that did the same, pedal would slowly sink to floor over a minute or so of moderate pressure, brakes worked absolutely fine on the road and queried it at mot time as I was concerned I had a problem, mot guy said don't worry they all do that!

 

[Wildefalcon]

The Volvo is the same, disconcerting.

 

[Moose McAlpine]

They're only short pipes down to the ABS pump, i'd just replace them.

I'm on my 4th Sprinter, can't beat them.

 

[arther dailey]

that makes sence