hand brake controls leaking

[shawn449]

I have a 2004 Mastiff..I swapped out my stock polished master cylinder controls for a set of Chromed controls they are also OEM Big Dog but in chrome.
Here is my problem they leak brake fluid, looks like from the vent holes. On mostly hot or humid days. I will go in my garage on a humid day and have brake fluid all over everything...Does anyone else have this issue and how can I fix it. I never had the issue with stock polished set...also at the same time I went to chrome master cylinder I also went with a new set of mirrors that has more style then function but it also required me to change the angle of the mirrors to see..I played around with adjusting the angle of the master cylinder on the bars so I could use the mirrors...could it also be the angle of the vent hole now? how should they sit on the bike vent hole higher or lower>??? any info will help..thanks

 

[Staffy]

Welcome, not certain if the ’04 controls are similar to the later models but here is what I would look at:
• Do try and find the source of the leak
• While sitting on the bike and the handle bar straight – I would like to have the top of controls parallel to the ground
• I would open the top cover to check the rubber seal – ensure it is installed properly, there is a groove around the lip, make sure it sits in there and also that you have the seal on correctly. Not sure if I can describe it correctly but….”bubble” side up. (Also on a side note: depending on how you bleed your brake line you could have "squisshed" the seal - always a good idea to open the top and check once you are done bleeding the line. I prefer to you to use a syringe and shoot brake fluid from the bottom caliper nipple into the master cylinder – when full put the seal on, pump a few times and there you have it).
• Brake fluid and paint don’t do very well together. So while figuring this our make sure you protect your tank or any other paint surfaces from getting in contact with the brake fluid.
• Also did you bleed the brake line correctly
Hope this helps and once again welcome
Staffy

 

[mobsta]

over filled?

 

[shawn449]

So far everything checks out the way you explained it..also its not overfilled and onlys seems to happen on humid/hot days?????

 

[Little-Boo]

When I replaced my control with chrome as you did, I had a slight leak coming from the Master Cylinder. I got me some speed bleeders and bleed the system over and over till I got all the air out. I also replaced that master cylinder cover seal. That was several years ago and have not had a problem since. Make sure that when you put the seal on there that no brake fluid is present on the seal before you put the cover on. If there is then you have over filled it. Hope that helps

Carlos

 

[Can-Dog1]

Shawn,

Some of the new BDM Master Cylinder covers are not true and will leak when it gets hot and humid. Best thing buy a replacement.

 

[PA Chopper]

Shawn,

Some of the new BDM Master Cylinder covers are not true and will leak when it gets hot and humid. Best thing buy a replacement.

This is what I ran into...a warped lid. I took the lid off and laid it on a flat surface and could see that the edges of the lid touched the surface but the center wasn't. I ran it across some sand paper in hopes of removing some of the chrome around the edges. Well I sanded and sanded and it wasn't enough to get the lid flat enough to stop the fluid from leaking. Finally contacted my dealer and got a replacement. He actually sent me the whole assembly which I installed and it has been fine ever since.