Master Cylinder - Refurb or Replace?

M

Midlifecrisis

Member
Hi all,

As the title really, I found a pool of brake fluid under the pedal, it is running down from the master cylinder. A quick internet search shows that I can get a seal kit cheaply, but looking at a few posts on here suggests that the bores can suffer badly from pitting (talking to myself now, but I need to get it off and have a look at it0.

All things being equal, should I refurb it of just put a new one on?

Cheers,
Mike
 
I'd get the bore lined with a stainless insert, and then fit a seal kit to it. If you're in a hurry you could fit a new replacement, and then get your old one sleeved at your leisure, ready for next time.
 
Hi Mike,

It may have already been resleeved in stainless steel, seals still wear over time and will eventually leak. Once you remove it and look inside, all will be revealed.

Ron.
 
Just to update, tis scrap :(
Still, taking off the reservoir has revealed some surface rust which will be better attended to, and the reservoir itself could do with a good clean. A nice shiny new cylinder will look better too.

I am not looking forward to bleeding the system though, the rear bleed nipples look to be out of the way somewhat.
Mike
 
Midlifecrisis said:
I am not looking forward to bleeding the system though, the rear bleed nipples look to be out of the way somewhat.Mike
Click to expand...

You're in luck then. There's only one, though it's out of the way on the top of the diff'. :wink:
 
If you're lucky you may get away just bleeding the front brakes Air shouldn't have got into the pipework serving the rear brakes
 
If a job is worth doing, then it is worth doing properly. The rear calipers are at the highest point, so most of the air that enters the system can be released from there. The balance will come out through the fronts, finishing off with the R/H side, being closest to the master cylinder.

Once the cylinder has been resleeved, it will be good for the life of the car. The seal should last longer too as the bore will always be glass smooth.

Ron.
 
Well, on that subject, I once had a master cylinder re-sleeved in stainless (Austin A30) & it had a lovely glass smooth finish on it's return to me. But it didn't work properly, the pedal would sometimes start sinking under pressure. After a couple of seal kits had been fitted, one of the guys in the best local factor we had (Harvey knows who) looked at it & commented that he thought the finish might be too good & fluid might be squeezing past the rubber on the super-smooth surface. A quick call to the Lockheed technical dep't confirmed this was the case & that a glass-smooth finish is the last thing you want in a hydraulic cylinder for the reason surmised. A quick hone & another seal kit cured the problem.
 
DaveHerns said:
If you're lucky you may get away just bleeding the front brakes Air shouldn't have got into the pipework serving the rear brakes
Click to expand...

If it were my car I would bleed the rear calipers until the fluid comes through nice and clean. That way you know that you have new brake fluid their, not fluid with with moisture in it which will corrode up the cylinders. Having just done the rear (dunlop) brakes on my Rover 2000, I can tell you that bleeding them every couple of years to ensure that the life is maximised is better than having to mess with the rear brake pistons.

James.
 
All done, the new cylinder is fitted (I will keep the old, where would I get it sleeved so I can have it as a spare??).

I bled the brakes right through to replace all of the old fluid with nice new stuff. My 10 year old enjoyed pumping the pedal.

That rear bleed nipple was, just as I had thought, a real faff!! I needed a stubby spanner and could have done with my hands being a few sizes smaller. Having Adam help probably saved the neighbours from some fruity language. The reservoir looks much cleaner and I put on nice new bolts and a new hose and jubilee clips.

Just enjoyed a test drive and the brakes feel fab!
Thanks for all of the advice.
Mike
 
Hi Mike,

Sounds like a pleasing outcome :)

Just one question, the new hose that you installed between the reservoir and master cylinder. You didn't use fuel hose did you? Reason being, brake fluid will eat (best word to use) non brake fluid specific hose, leading to a rapid demise of the hose and air and moisture entering the system.

The hose for this job must be proper brake fluid resistant hose, and is generally only available from brake businesses, and even then not often. Reason being is that very few cars have their booster/master cylinder/reservoir separate, so the need for a length of brake hose to join items is not at all common, certainly not like it once may have been.

Ron.
 
SydneyRoverP6B said:
Hi Mike,

Sounds like a pleasing outcome :)

Just one question, the new hose that you installed between the reservoir and master cylinder. You didn't use fuel hose did you? Reason being, brake fluid will eat (best word to use) non brake fluid specific hose, leading to a rapid demise of the hose and air and moisture entering the system.

The hose for this job must be proper brake fluid resistant hose, and is generally only available from brake businesses, and even then not often. Reason being is that very few cars have their booster/master cylinder/reservoir separate, so the need for a length of brake hose to join items is not at all common, certainly not like it once may have been.

Ron.
Click to expand...

Hi Ron,

Thanks for the concern, I probably would have made that mistake but I did a bit of research on t'interweb before starting. I bought the right hose from Wins.

Mike
 
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