Newbie Question: Changing Brake Master Cylinder?

Hello Moparters,

Thanks much for your help this week on my water pump question. I'm ready to tackle that one this weekend.

I would also like to attempt replacing my brake master cylinder. This doesn't look too hard, but wanted to check with those who have done it to confirm. If not, I'll bring the car in to have it done.

My car has a power booster, but that is working fine for now. I know the master cylinder is going, since I can see the traces of brake fluid it has dripped.

Will I need any special tools for this job? Do I just basically unbolt it from the booster and remove the two brake lines?

And then for re-install, the reverse, but need to bleed out the cylinder first? Are there any other adjustments or steps I'm missing?

Do I need to do anything with the piece (push rod?) that goes into the booster?

Thanks again for any tips or pitfall advice. I really appreciate the help for a newbie to this stuff. Hopefully I'll be up to speed soon!

--Stan

simple swap and bleed the master before hooking up the lines. Most new cylinders come with a bleeder kit. Two hoses and a pair of adapters.

Ok, Thanks.

So, I should bleed the Master Cylinder before installing (bench bleed?) and then bolt on and bleed at brake lines?

Will I need to bleed at the Brake Wheel Cylinders as well with a Master Cylinder swap ?

Also, I saw instructions that said to stick a dowel in the back of the master cylinder while bleeding it. How does that work?

Thanks much for any advice. Learning....

--Stan

You use the dowel to push on the piston while bench bleeding(I've always used a phillips screw driver).After you install the master cylinder have a helper push the brake pedal and crack the lines open until the pedal reaches the floor,then tighten the lines BEFORE your helper lets the pedal off the floor.Do this a couple times and thats usually all the bleeding needed.If after this the pedal feels spongy bleed at the wheels.

Ok, great info. Thank you.

Do I need to seal off the brake lines in some way when I remove the old master cylinder? Will air get in the lines otherwise?

And do you generally just use a regular open ended wrench to loose the lines? I've seen an article that says to use only a special brake "line wrench", but I am not sure if they are referring to more modern cars.

Thanks again!

--Stan

No need to seal the lines. A line wrench is just a heavy duty boxend with a slot cut in it to slide over the line. It isn't necessary.

Great info! Thanks for the help! I'll try this tomorrow.

So, looks like I won't need to bleed the brakes at the wheels unless something doesn't feel right after the master cylinder is back on, correct?

And if I don't bleed at the wheels, about how much old brake fluid remains in the lines/wheel cylinders? Is most of the fluid in the master cylinder itself?

thanks again!

--Stan