Front brake lever keeps going soft around 3days after bleeding. no leaks visable, lines and pads looks ok. trying to figure how to troubleshoot master cylinder isssues. or of it a problem with the master diaphragm. any help would be greatly appreciated. just trying to avoid taking into a dealer if its something simple that i can do myself. Fluid comes out clear without any bubbles when its bled.

 

Getting air into the line somewhere. Is the reservoir seal in good shape; no small cracks? Caliper pistons/seals clean and lubed? Good seal on your bleeder screws? How old are the brake lines; what type, OE or s/s?

 

as mentioned by Jeff above, and have you flushed the system and placed new fluids in? Contaminated brake fluid is a bear to deal with and the system should be flushed yearly.

Welcome to KF

 

bike brake lines are still all stock. i did have some brake fluid i had on the shelf that i opened last yr that i used to top off when i bled the brakes this yr. Maybe i'll get some new fluid and a vac. bleeder and repeat bleeding steps again and see what happens. do u all know how to troubleshoot a faulty master cylinder? If i can just find out if thats the issue, i will get a kit and rebuild it, if thats not the issue, i will replace the brake lines/fluid. thanks for responding.

 

just a thought. when your brake fluid (in the bike) has been there awhile, the moisture tends to condense behind the caliper piston. You also get very small traces of black rubber which come from the inside of the OE lines and congregate in the caliper. When you have bled the lines, how MUCH did you bleed them? I would recommend getting a fresh bottle of Castrol LME brake fluid, and pumping it through your lines (from "top down" not from the caliper up) to completely purge any contaminated fluid and/or rubber deposit. Go through about 2 complete fills on your master cylinder and flush the lines. Make sure you get only clean fluid (no bubbles) coming out the bleeder catch tube. (Seriously; bleed them till you're sick of it.) I'm not convinced your master needs a rebuild. They WILL go bad if you leave them empty and dry--and the seals rot, but tend to live long if fluid is kept in them.
If that still doesn't work, double-check your banjo connections on the brake lines and/or replace the sealing washers, if you're on a budget (hey, we all are) and not up for spending bucks to convert to stainless lines.
Keep us posted, OK?

 

Brake fluid is hygroscopic, so you have to use it or lose it. It will absorb moisture once opened. The moisture causes all kinds of brake issues and soft brake feel is just one of them.

 

Thanks jeff and dragone for the tips. I definitly had black fluid come out after I bled the brakes for the 1st time. So I'm going to get some new brake fluid and bleed the dog crack out of those lines lol.. Hopefully that will do it, I'll keep U all posted. What will be the symptoms of a faulty master cylinder? If this does not work!! Thanks again guys.

 

[QUOTE=I'm not convinced your master needs a rebuild. They WILL go bad if you leave them empty and dry--and the seals rot, but tend to live long if fluid is kept in them.
QUOTE]

How long is too long? I pulled my front caliper off (08 KX250F) because there was something dragging. I let the brake line hang over a bucket with the reservoir cap and bladder just sitting on the reservoir not screwed down. I went to work the next day to disassemble the caliper (no air at the house) and clean it up. After getting home the reservoir was empty. I reassembled it all and bled until no more air out came of the bleed on the caliper. Held the brake lever to the bar, cracked the relief briefly and closed. Lever is still mushy.

Having no fluid in the reservoir overnight is not long enough to dry out the seals is it? It probably never got over 40 degrees in the garage while working.

Thanks.

Jeff

 

You'll need to keep bleeding it until you get the last of the air out. Overnight isn't enough for the seals to perish, but you will definitely have air in the system. Use fresh fluid, of the right grade (DO NOT MIX GRADES) and keep going.

 

Thanks Dark Angel,

I have reading a lot about this situation and I wish I would have let the reservoir cover on screwed down so to create a vacuum. I think tonight I will try tie rapping the lever to the handlebars and leave that for a while. Sounds like people have had success doing that. Plus it is full moon and we are going to go for a ski!

Jeff