Bleeding brake, air in system

[JeremyT]

Hi all

I have started work on the brakes of my Morris which have not been used for sixteen years.

I've sought advice from the forum before and replaced all the relevant parts that needed changing, so pretty much all of it.

The only part not changed is the master cylinder which I thought I'd give the benefit of the doubt.

But after three separate bleeding attempts there is still air in the system. The brake pedal appears to have some compression but then it does not.

Can I put this down to the master cylinder which is probably the original? And should I just replace it?

Or could there be another issue?

Many thanks

Jeremy

[SteveClem]

If the mc hasn't been used in all that time it could be dodgy. And they're not that easy to get to..

[kennatt]

what normally happens with age/long layup is that the water in the fluid sits in the bottom of the m/c and causes corrosion of the bore,so on use the corrosion damages the rubber seals as they travel down the bore.This can cause air to enter the system and ,more normally,. leakage from the m/c. Even with a system that is ok,if you need to bleed the system,because of the pumping the pedal procedure,the rubbers are made to travel down the bore past their normal travel point and...onto the rough area of the bore and .......as above. I would change the m/c ,,if it was mine

[IslipMinor]

Jeremy,

'Fraid so, new master cylinder is required, but even then they can be a real pig to bleed.

[philthehill]

It helps the bleeding process if you can get the front or rear as high off the ground as possible as air will go to the highest point in the system/pipework.
Once had to get a Minor nearly vertical so as to get all the air out of the rear brakes.

[JeremyT]

Hi all

Many thanks for all advice, mc change it is.

Jeremy

[JOWETTJAVELIN]

Just to add to the good advice, start bleeding at the wheel furthest from the master cylinder and work around. Certainly a full brake overhaul is in order in this case. You might want to consider using silicone brake fluid if you do renew the entire system.

[Declan_Burns]

The repro M/C's can be a tad too wide for the chassis and need to be ground back to fit.
Regards
Declan