Brake master cylinder replacement guide 4th gen
Posted: Mon Apr 22, 2013 10:51 pm
Just a quick quide to replacing the BMC, i know its an easy job but it might help someone, so here goes:
You will need a 10mm flare spanner for the brake lines. its worth paying £8 or whatever one costs to save the headache of possibly rounding off one of the nuts.
so the BMC is circled here in green. it connects to the brake booster (the big black circular shaped thing behind it) with 2 bolts.
First, remove as much of the brake fluid from the cylinder as possible, i used a turkey baster. Make sure you dispose of it properly and keep in mind it will strip paint. its nasty stuff. i recommend getting some old rags or towels down under the BMC as you will get some fluid leak when you remove the brake lines.
I had to undo my strut brace to get to it. as you can probably tell on mine by the cable ties, my clutch cylinder (circled in orange) is just tied to the strut brace fixing. on the lude i removed the BMC from there was a little attachment under where the strut brace bolts to the chassisthat holds the clutch cylinder, (circled in yellow) its just a case of undoing the 3 bolts and popping it all off.
Next i removed the bolt and unscrewed this connection on the fuse box and pulled it out by unclipping it at the back, there is still stuff attached, but you can move it enough to get to the bottom bolt on the BMC.
Once that is out the way, crack the 2 bolts holding the BMC in place (you cant really seem them with the pics, but they are easy enough to locate), and then crack the brake line nuts (circled in green). undo the bolts holding the BMC in place fully, so as soon as the brake lines are off you can pull it out, as brake fluid will start dripping from the BMC.
One thing to check for as i didnt notice it until i got a second master cylinder from ebay, is on the piston is a black ring that you can slide off, the BMC i removed from the car didnt have one and neither did the one i got from the scrap yard, im wondering if the absence of that part was what was causing my loss of pressure. circled here in green.
Then pop the new BMC on, screw in the brake lines, tighten it up, refill it, refit the fuse box reserve cylinder and strut brace and bleed the brakes. job done.
You will need a 10mm flare spanner for the brake lines. its worth paying £8 or whatever one costs to save the headache of possibly rounding off one of the nuts.
so the BMC is circled here in green. it connects to the brake booster (the big black circular shaped thing behind it) with 2 bolts.
First, remove as much of the brake fluid from the cylinder as possible, i used a turkey baster. Make sure you dispose of it properly and keep in mind it will strip paint. its nasty stuff. i recommend getting some old rags or towels down under the BMC as you will get some fluid leak when you remove the brake lines.
I had to undo my strut brace to get to it. as you can probably tell on mine by the cable ties, my clutch cylinder (circled in orange) is just tied to the strut brace fixing. on the lude i removed the BMC from there was a little attachment under where the strut brace bolts to the chassisthat holds the clutch cylinder, (circled in yellow) its just a case of undoing the 3 bolts and popping it all off.
Next i removed the bolt and unscrewed this connection on the fuse box and pulled it out by unclipping it at the back, there is still stuff attached, but you can move it enough to get to the bottom bolt on the BMC.
Once that is out the way, crack the 2 bolts holding the BMC in place (you cant really seem them with the pics, but they are easy enough to locate), and then crack the brake line nuts (circled in green). undo the bolts holding the BMC in place fully, so as soon as the brake lines are off you can pull it out, as brake fluid will start dripping from the BMC.
One thing to check for as i didnt notice it until i got a second master cylinder from ebay, is on the piston is a black ring that you can slide off, the BMC i removed from the car didnt have one and neither did the one i got from the scrap yard, im wondering if the absence of that part was what was causing my loss of pressure. circled here in green.
Then pop the new BMC on, screw in the brake lines, tighten it up, refill it, refit the fuse box reserve cylinder and strut brace and bleed the brakes. job done.
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