Front Brake issue?

[DLSSOJC]

   I have noticed lately on my 2000 Interstate with 23K miles that the front brake lever sometimes gets excessively hard to pull (very tight). This causes the calipers to put some pressure against the rotors and drag. I have already took apart and cleaned and made sure the front calipers are not sticking. It appears that when the brake fluid warms up after riding or sitting in the sun in this 100+ degree weather, the fluid maybe expanding some and either the mastercylinder is not letting the pressure off, or the inside of the brake lines are collapsing?  I have not taken the mastercylinder apart yet to look closely at the insides, but this may be my next step.

I got on it today after it had been sitting out in the sun for a couple of hours and the lever was very tight, and pressure in the front lines seemed to be causing the pads to drag against the rotors some. After riding a few miles and not trying to use the front brake at all, I checked the lever and it was back to normal with the normal slack in the lever and not dragging the pads.

Has anyone experienced these symptoms before? I read one place where someone said the vent in their mastercylinder was clogged up one time causing similar symptoms?

Thanks for any help. 

[bentwrench]

It sounds like the piston in the m/cyl. isn't returning all the way.next time the lever feels hard open a bleeder screw and see if the problem stops.If the piston doesn't come back far enough to expose the little return port pressure will remain in the lines.It's most likely some gunk or corrosion in piston bore.
bw

[DLSSOJC]

That's what I am leaning towards. I am going to take the mastercylinder apart and see what I can find.

[sandy]

Try removing all the fluid with a Mity Vac. Refill with alcohol and flush all of it out again. Then refill with DOT 4 and bleed the system. This will get rid of all the moisture in the system. It could be moisture is expanding when it heats up.

[DLSSOJC]

I have already removed all the fluid with the Mityvac and replaced with new fluid. I didn't flush with alcohol though.

[Ricky-D]

I do not subscribe to the practice of introducing alcohol into the brake fluid system.

Reasons being that alcohol is water (based) and is a contaminant.

You cannot get all the "contaminant" out regardless of how much work you may do.

so the fresh brake fluid that you refill with is going to be contaminated from the git-go.

***

[Former BMW Guy]

I agree.
Never introduce anything but approved brake fluid into a braking system.
If you are going to flush...use brake fluid; its cheap enough.

JP

[salty1]

For the record, alcohol is not water based. Its an organic substance. However, it is a hygroscopic substance and water is quite miscible with alcohol. I agree that using alcohol in the brake system is probably not a good thing. FWIW. 

[salty1]

Is it possible that your reservoir is overfilled?   

[DLSSOJC]

Is it possible that your reservoir is overfilled?   

I don't think so. I reflushed the system out and added new brake fluid to the specified level. I think the vent in my mastercylinder may be clogged. I am going to take it apart and see what it looks like inside.

[RP#62]

I do not subscribe to the practice of introducing alcohol into the brake fluid system.

Reasons being that alcohol is water (based) and is a contaminant.

You cannot get all the "contaminant" out regardless of how much work you may do.

so the fresh brake fluid that you refill with is going to be contaminated from the git-go.

***

That's generally good advise unless you're trying to remove contamination.  Flushing with clean fluid will not do that.  Short of replacing the lines, about the only way to remove contamination is with a denatured alcohol flush followed by blowing the lines out with dry compressed air.  Folks have been doing that for years with good results.

-RP

[DLSSOJC]

I took the front mastercylinder off today and took everything apart. Everything actually looked pretty good in there, with just some minor debris, so I cleaned everything up. All the rubber boots and parts looked very good. I reinstalled and bled the brakes and everything felt normal. I took for a test ride and about 8 miles down the road the brake lever started getting very tight again and the calipers started putting pressure on the rotors again. So I pulled over and opened up the front right bleeder screw for a second to let the pressure off and everything went back to normal again. I rode back home with no problems and brakes felt fine again. I wonder if the problem may be in the front brake lines with the internal walls breaking down or trying to collapse? I have heard of others having these same symptoms with a brake line problem? Anybody else ever have this happen to them?   

[Hoser]

I had a car that did that, replaced the rubber portion and fixed it.  Sounds like a new brake line will fix you up.  Hoser 

[sugerbear]

if you can, spring for the braided lines. better feel and better control over braking.