Front brake concern

[yhet43]

I've just recently changed my stock front brake lines to the steel braided ones and i used a new type of fluid...the DOT-5.1 type. It indicates that it mixes well with dot-3 & 4 fluids.. but i drained the old fluid just the same before filling her with the dot-5.1. My front brakes were excellent in terms of stopping power! Braided hoses really are the best way to upgrade your front brakes.

There is one concern i have...it seems that my front brake master cylinder piston is not depressing or should i say, returning to it's extended position whenever i squeeze my brakes, for like just a few millimeters or so...so, what happens is, my rear brake light stays on and goes out only when the piston depresses or returns to it's standby position fully extended, and that's for...oh, like about a minute and a half. I'm not sure if it's the same when i'm running.  I raised my front wheel to see if it's locking my brakes, and it doesn't seem like it, cause she still turns freely...

Could it be the fluid being of a different grade? has anyone had the same problem? Hope you can give me tips on what to do... I was thinking of draining the new fluid and using the usual dot3 or 4 and see if it changes...

[guntherrex]

I think it has a spring return, your master cylinder might be sticking, maybe the rubber seal is stuck in there or the spring has perished. better have a look inside

[rigwit]

Are you sure its DOT 5.1 or silicon synthetic?

 When brake fluid i.e. DOT 3, 4 or 5.1 is exposed to the atmosphere it absorbs water; this lowers the fluid boiling point which can have dire consequences. The other problem is when fluid is absorbing water it also forms a gooey crud that can block master cylinder return parts, causing rusting and seizure of pistons; costly items to repair and put right. DOT5/ Dot 5 silicone high boiling point, non hygroscopic, kind to paint work....but But-big BUT. Shake it up and it holds air bubbles (very small bubbles but they are there) and it takes days to get rid of them, also being silicone based, it's not a good lubricant and doesn't help piston return in your master cylinder. Bottom-line...Most machines come with DOT 4 brake fluid in brake systems, it is not a “sealed set it and forget it system”, it needs maintenance. changing every year is a must for the paltry cost of fluid and if done right piece of mind.

[91cb-1]

I agree with above quote and would add that instead of draining the fluid and replacing it bleed straight through, your calliper is a complicated piece of equipment and air can get trapped in it, if you drain your fluid you're filling your line and calliper with air and then filling the same with fluid trapping air in the system which you then have to bleed the whole system but i would stick to dot 4 fluid. you have a 21 year old bike designed with dot 4 fluid brake system, newer brake systems designed for dot 4 might be suitable for 5.1 but ours is not i would say

[yhet43]

Thanks for the replies guys... I'll seriously consider your suggestions. I'll try putting back a dot4 fluid and hopefully see if she goes back to the way her brakes were working. Hopefully it'll do, i didn't have a problem with it before i changed the brake line and the fluid. If that doesn't work, then i'll have to open her up.
 

[rigwit]

I agree with above quote and would add that instead of draining the fluid and replacing it bleed straight through, your calliper is a complicated piece of equipment and air can get trapped in it, if you drain your fluid you're filling your line and calliper with air and then filling the same with fluid trapping air in the system which you then have to bleed the whole system but i would stick to dot 4 fluid. you have a 21 year old bike designed with dot 4 fluid brake system, newer brake systems designed for dot 4 might be suitable for 5.1 but ours is not i would say

I would personally break the master cyl joint to pipe and drain master cyl resi and clean grunge thataccumilates at lower internal casting points,the assy joint leave just cracked fill master and gravity will allow fluid to flow, just make shure you have a rag or receptical to catch drips-dog up joint, then fully purge out the old fluid knowing no old or crud is gonna be forced in.

[yhet43]

I agree with above quote and would add that instead of draining the fluid and replacing it bleed straight through, your calliper is a complicated piece of equipment and air can get trapped in it, if you drain your fluid you're filling your line and calliper with air and then filling the same with fluid trapping air in the system which you then have to bleed the whole system but i would stick to dot 4 fluid. you have a 21 year old bike designed with dot 4 fluid brake system, newer brake systems designed for dot 4 might be suitable for 5.1 but ours is not i would say

I would personally break the master cyl joint to pipe and drain master cyl resi and clean grunge thataccumilates at lower internal casting points,the assy joint leave just cracked fill master and gravity will allow fluid to flow, just make shure you have a rag or receptical to catch drips-dog up joint, then fully purge out the old fluid knowing no old or crud is gonna be forced in.

Thanks for the tip!

[guntherrex]

5.1 is not recommended for dot 4 systems, might eat away the seals. haven't tried yet though. better replace

[yhet43]

Okay. will do. Thanks