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Bleeding brake, air in system
Posted: Mon Oct 24, 2016 6:15 pm
by 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
Re: Bleeding brake, air in system
Posted: Mon Oct 24, 2016 7:25 pm
by 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..
Re: Bleeding brake, air in system
Posted: Tue Oct 25, 2016 9:01 am
by 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
Re: Bleeding brake, air in system
Posted: Tue Oct 25, 2016 9:26 am
by IslipMinor
Jeremy,
'Fraid so, new master cylinder is required, but even then they can be a real pig to bleed.
Re: Bleeding brake, air in system
Posted: Tue Oct 25, 2016 5:05 pm
by 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.
Re: Bleeding brake, air in system
Posted: Tue Oct 25, 2016 5:19 pm
by JeremyT
Hi all
Many thanks for all advice, mc change it is.
Jeremy
Re: Bleeding brake, air in system
Posted: Wed Oct 26, 2016 11:38 am
by 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.
Re: Bleeding brake, air in system
Posted: Wed Oct 26, 2016 4:17 pm
by 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