6th. Gen front brake locking up

So im cruising down the highway the other day when i notice im running low on power....... twisting the throttle really has no effect. As i pull to the shoulder, the front end is shaking pretty good. Front brake lever is rock solid, and will only pull back about 1/8"

Turns out the engine is of course just fine, the front end shake and lack of power was caused by the front brake being stuck on.

Popping out the tool kit i crack open the bleed valve on the right front caliper and get a nice shot of brake fluid coming out. After that, the lever returns to normal, and the bike will once again roll. I ride to my destination and back without issue. A total of about 20 more miles.

Anyone care to explain this ? The bike is all stock. 2003.

I suppose my next move will be to bleed the brakes. OH JOY. Linked brake bleeding....

 

Sounds like your front master cyl is not releasing. I don't think that bleeding is the answer, unless flushing old gunky fluid out frees up the m/c.

 

i hear what your saying, but i dont think its caused by the master siezing. It wasn't just the hard lever, it was also actuating the caliper. Almost like the fluid is crap and was boiling, causing it to expand in both directions......

 

Boiling fluid will cause the lever to move freely, as if there were no fluid in it. I've seen this before. Everyone tried to tell me that I had a bad caliper, but no, it was the master cyl not allowing fluid to return to the reservoir when the lever is released. To test this, squeese the lever several times and see if it does it again. Then, crack the line at the m/c (do NOT let fluid get on the paint!!). If the m/c is bad, it will release the brake and a squirt of fluid. If it won't do it again, it may have already cleared the obstruction.

 

It's about time to bleed them anyway, if that makes it easier... Did you check the level in the master cylinder reservoir when you got home? If it is high, the brake fluid has probably absorbed water and expanded, which it is prone to do in a damp environment (Grover Beach is by Grover City / Pismo Beach?). If so, your comment about the fluid boiling/expanding is somewhat accurate. Brake fluid expands as it gets hot, which is why there should always be some air space in the reservoir when it is topped off, i.e. avoid overfilling. It is probably worth taking a good look at the reservoir seal and surfaces. It doesn't take much for them to get leaky enough to become problematic.

Eddie VT makes a good point, too. I would still flush out the old fluid, though.

 

http://www.jsautorepairs.co.uk/BrakeFluid
Here is a little info on how water acts on brake fluid and how the lever would feel if your fluid was boiling. Yeah, this is mostly about cars, but your system is virtually the same. Hope this helps.

 

Thanks guys for your thoughts. I really dont think the fluid was boiling, that was only my rationalization of what could have caused it. Anyway,..... it is time to flush fluids anyway.... the problem has dissappeared for now, so i may never really know the exact cause.

 

Oh no you don't! One more link to support a theory;

http://wiki.answers.com/Q/Why_would..._and_the_brakes_lock_up_after_driving_4_miles

 

Sounds interesting about the brakes. I had my back brake being a little touchy once in awhile. Ended up changing the fluid and works much better. Never really messed with the linked brakes, might look into doing some stainless lines and getting rid of the linked brakes. Good luck resolving the issue.

 

I have some serious reservations concerning the possibility of boiling the brake fluid. Unlikely that water in the brake fluid caused the issue. There are some additional factors involved with "power" automobile braking systems that are different from the closed system of the VFR....just thinking out loud.......

 

Stuck caliper piston causing drag OR stuck proportioning valve

 

After re-reading (is that a word?) this thread and my first post, I feel compelled to clarify my original comments. I wasn’t very clear on what led me to my conclusions. Forgive the somewhat structured and tutorial-like approach, but I am sad to say that I actually do think this way.

Assuming that Tori has ridden the bike more than once, and he assured us that he had, this has never happened before, nor had he changed anything such as fluid levels since the last time he rode. After he relieved the pressure in the system, it did not reoccur.

Hydraulic fluid in a closed system expanded to the point of pressurizing the system. Heat was the cause of expansion.

The pressure build-up had to be either between the calipers and the master cylinder, or it was system-wide.

If it was between the calipers and the master cylinder, fluid could not flow past the piston in the master cylinder reservoir. The cause would be either blockage of the fluid return orifice by a contaminant, or the master cylinder piston not being able to return to its static/non-actuating position, most likely by the same condition (contaminant of some kind).

If the master cylinder return orifice was not obstructed, then the problem was a lack of air volume for the fluid to compress as it expanded. Where could the volume of air have gotten to? It was either gone, or compressed more than it had been up to that point in time.

Given the fact that DOT3 and DOT4 brake fluid is hygroscopic by nature, as in it readily and happily absorbs water around seals and through rubber hoses, it is possible that enough water had been absorbed over time to eliminate the air volume necessary for system expansion. Kind of the straw that broke the camel’s back, in this case.

The fluid would not have to boil to create the problem, just expand to the point of causing pressure to build. As eddieVT pointed out, water boiling would create vapor pockets, and things would get spongy instead of firm.

It is hard to imagine that brake pad wear would not offset any fluid volume gains, but screwy things happen sometimes. My viewpoint says that eddieVT’s original guess at the piston being in the wrong place/orifice being blocked is probably more likely. The only thing left, if that was not the case, is too much fluid/not enough air. What supports that argument is the fact that the brake lever could not be moved.

As an additional thought, if brake pads are changed at some point with the original fluid undisturbed, water absorption could become a key factor, particularly if the new pads are a bit thicker than stock.

There. That’s better.

 

I'm with Kia001 on this one, sorry LGN001, nice tech paper though....

 

Well, I can see that it is a complete waste of time trying to change YOUR mind... :biggrin: :smile:

I forgot about the linked brakes/proportioning valve, but I don't think that a sticking caliper would raise the system pressure...

In any event, technical problems are good for the mind, but not necessarily the ego.

 

I am willing to listen and if the information is viable, I would be more than happy to change my position - I'm always looking for good new ideas. I could be way off base too, hard to say when you are just basing your ideas on past experience. BTW - I rode a bike 10 miles through the desert with a locked front wheel due to a stuck caliper, after having bled almost all of the fluid out of the system during an unsuccessful, and unplanned, midrace pitstop......the problem was definately not fluid related :biggrin:

 

Yeah, me too. I can't tell you how many times I have been convinced what a problem might be caused by, and find out that I wasn't even close...

 

boiling brake fluid??:wacko: man sounds like a serious 24 hour roadrace..:mod: if that happened were your rotors smoking?? could warp them you know if you did outta balance pulls that side.sounds like your piston in the brake caliber was stuck out maybe rock dirt what ever you stopped bleed it took pressure off then it worked if i were you:attention: id clean the calibers check the pads and change your (boiling fluid) just to be safe :attention: are your levers damaged pushing in on the master cylinder?? you know the adjustment inbetween settings pushes it did you adjust on the fly?? thats a seriuos issue could get you hurt do you have the abs model if so take to shop f that thing..hope you find what it was maybe you can get rotor protectors off the dirt bikes so no more debrie gets in there :mod: good luck man that sounds really scarey haveing involuntary front brake siezeing on you man....im gonna have bad dreams..

 

Christ,...... can i get a do-over on the whole "boiling" thing.

Thanks for all the thoughts guys....... i'll let you know if i find a cause.

 

If he had a stuck caliper, cracking the bleeder would have had no effect, he still would have a stuck brake. But, when he did crack the bleeder, the brake released. When my old '83 did the same thing, EVERYONE told me I had a stuck caliper, but I was sure they were wrong for the reasons I just mentioned. I rebuilt the master cyl, and problem gone. When the lever is released, the fluid has to be allowed to return to the M/C reservoir. If not, the brake will remain applied. Bleeding might flush out the M/C enough for it to work, but I had to rebuild mine before it would allow the brake to release. I can't wait to find out what fixes it.

 

I think your theory is the most correct eddie. I can certainly see things going exactly as you described. Hence it was a sporadic problem, and has not reoccured "yet". I will bleed it an see what happens.

on a side note: the fluid level was between the lower mark and the full mark. Fluid is browning, but no contaminents could be seen in resevoir.