How hard is it really to change a master cylinder?

69 dodge coronet, already have the part from Napa

I know I need to bench bleed it first, but is there anything I need to know before I tear into this?

When I come to a stop (automatic) I push on the brake and it slooooowwwwllyy depresses all the way to the floor. It's getting more scarey and it's time to be changed!

thanks!

eight

Like you said bench bleed it, until the fluid runs clear. Also before you start make sure that you can loosen all of the wheel cylinder bleed screws. If the brakes haven't been done in some time the little bleed screws can break. Also a good time to check the rubber hoses for cracks.
Bleeding the brakes on the car is a two person job, unless you have the special tools for a one man bleed. Just make sure the person in the car pushes all the way to the floor, and HOLDS the pedal down until the bleed screw is tight again. Generally bleed the furthest away from the master cylinder first.

Yeah, if no brake fluid is leaking anywhere , your MC is bad. Really not a bad job; especially if its power brakes. Bolts to the booster under the hood. If they are manual, the worst part is reaching the bolts inside on the fire wall. It's easier with a helper. Otherwise, everything else is the same; Bench bleed, install, bleed rest of the system.

Bench bleed the new cylinder, attach it to the lines but do not tighten them.
Have a helper push the pedal down then snug up the lines..
Then you can bleed the system at the master culinder lines and avoid trying to break off all 4 bleeder screws...
Simply pump up pressure and loosen the line at the front or back line until no air escapes when you crack it open..Keep refilling the cylinder as needed.
Do one line at a time until you have a solid pedal.

Since no one else said it use some penetratibg oil on the lines to the master also.Lots of times the fittings wont turn and the lines will snap off.That and use a line wrench on them.Rocky

I bought a set of Speed Bleeders and they are GREAT,they make it a 1 man job.You remove your bleeders and install these,then you loosen 1 and I attached a clear hose to a plastic bottle and push the pedal.I pumped the pedal with the bleeder SLIGHTLY open and it allowa fluid out and when you release the internal check valve closes.I leaned over and watched and it wh\ould go clear....then you know it's bleed.THEY really do work,it makes it a 1 man job...

Try tightening the bleeder screws slightly before loosening them.
I wrap a little teflon tape around the bleeder screws so as to form an airtight seal around them. Then I use a mighty vac vacuum pump and bleed the brakes that way. Makes it a one-man job.
MAKE SURE you correctly install whatever type of push rod retainer is used for your application. Some use that little rubber piece that slips over the push rod and snaps into the back of the master; some use a screwed on retainer at the back of the master. Sucks when your push rod falls out of the master cylinder, especially when hitting the brakes at top end of a drag strip (DAMHIK! lol)

don't use teflon tape, it is a flared fitting. If it leakes, the threads won't help, and you have to check the face for cracks or something.

Some guys have used vacuum line as the pushrod retainer a big NO-NO as many times they are layered, and when you hit the brakes hard, that outter shell of the line just slides off the ones inside it..