Rebuild dual line brake master cylinder

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T

ThomasLRNL

Member
Posts
53
Hi all,

I have a weird brake issue. Brakes worked fine for atleast half a year. Suddenly, the pressure is inconsistent. Hard, then i drive a minute without having to brake; soft as a napkin. can pump them up again to come to a standstill.

Someone able to explain this inconsistenty to a certain part/problem? I wouldnt say air in the line, since how would it have gotten there? Im running these brakes for a long time. Anyways, if nothing comes up ill rebleed them again, but wanted to know some experiences before i went and did it.

Cheers!
 
As said they do not auto adjust, so you need to adjust them.

If any wheel takes more to adjust then that wheel brake might have an issue.
 
Hi all, checked the shoe adjustment; which was not it.
the problem got worse overtime, and suddenly i could clearly hear fluid gushing through seals when i pressed the pedal. So, master brake cylinder. I have a 109 dual line system. Where one fitting is larger than the other. See photo.

I am trying to open it to see which rebuild kit is available for it, since a new one is very costly. However i am stuck at a large hex type fastner, which needs a large allen key. its located in the part where the reservoir attaches to the metal part. Its very stuck, but most of all. Ive never seen anything like it online. Anyone has an idea? i also have no serial numbers or anything of the sort.

IMG20241009184802.jpg
 
Symptoms you have are of failed seals in master, it will be worth doing slave as well because bits of master seals will have found their way down the system. Scotts classic car Spares have a range of seal repair kits, find on the flebay. A bit of heat can help free the Allen, just some boiling water if you are worried about using a flame.
 
I checked scots classic car spares, but they dont have what i need.

Also, the rebuild kit from paddock only comes with two rubber seals. Are there not more inside the unit itsself? i took the old one apart but cannot get the plunger out to check. In other words, is the paddock spares kit complete? See link below!

www.paddockspares.com

Seal kit for 90577520

607726 Seal kit for 90577720
www.paddockspares.com www.paddockspares.com

i would love to hear experiences of people who rebuild their master cylinder, i can find very little info about my specific one.
 
If it is an odd one and will not come apart with ease I suggest you bite the bullet and look up John Craddock as the have a good range of series parts
 
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