The last couple of rides iv been on my front brake has been giving a bit of trouble, wondering if anyone can enlighten me on the subject. Its on an 08 TXC450, after awhile riding (around a half hour or so), the front brake seems to start coming on by itself, right to the point (after about 5 minutes) of locking up completely.The brake lever is also solid at this point, cannot even pull it in. I then leave it for a while to cool down and it releases again back to normal, well until it gets hot a again and locks up. Iv tried bleeding the system, replaced the fluid but it still seems to do it. Anyone got any ideas? Would be much appreciated
It could be a damaged or internally collapsed brake hose that is acting like a check valve and will pump up the brake just like you described.
Are you making sure that the level isn't too high in the reservoir? I've had front brakes lock up and dump me after changing out brake pads and not adjusting the level of the fluid after putting the thicker pads in. If you are bleeding out fluid out on the trail after each incident, to get your brakes back and that still doesn't help, then it is something else.
Yea, have been playing round with the lever freeplay to no effect. resevoir level iv tried at the max mark and at the mininmum mark and still does it. Is it a fairly common occurance for the hose to fail internaly? It is 3 years old now, do the deteriorate over time? Have just had the caliper off and checked all the slides and pins, all seem clean and everything is sliding alright
Next time the brake pumps up crack the bleeder screw and see if it relieves the pressure. If it does it's most likely the hose, if it's still locked and there was no pressure at the bleeder the problem is in the caliper. The hose could get damaged from catching or hitting something in the woods, it does not have to be an age related failure.
contamination of fluid- liquid or solid. #1 cause of swelling shut brakes. and as DD pointed out someone may have added fluid before new pads were installed. so- when the pucks are pushed back in the level goes up. then, there's no room for it to expand, so, the pressure has to go somewhere. also- on some m/c's there's a "high" and "low" indicator. that tells you how much pad life you have left. never add fluid. just replace the pads, the fluid will come back up when you do same. if you have to add fluid you have a leak and it's shop time. change the fluid only, never top-off during the normal course of service/inspection. if the fluid ever gets low you need pads or have a leak. wash the bike and get the brakes spotless. then, remove and tear down the system- everything, and get a new line and blow it out then flush it with fluid, and clean it all in the intended fluid you want to use. use several seperate stations for outer stuff and inner stuff. be surgical. once you get it right you can forget about it and get back on with life. brakes are something i wont even begin to skimp on- safety freakin first! they are often the most neglected, punished and butt simple thing on the bike. if they start acting up on a customers bike i remove them. the whole system. and, attack it 100%, new hoses, seals, everything. no screwing around and no magic bullets. they get a complete overhaul. esp if it's a kids bike. if the owner is looking for a shortcut i direct them down the road, etc. nothing is more important than bullet proof brakes. the current brembo's i've seen over the past several years are just incredible!
I do not recommend pushing old fluid back into the master cylinder by squeezing brake pads back. This method will send any trash or corrosion that has accumulated in the caliper into the master cylinder. The better method is to open the bleeder before pushing the caliper piston back and force the old nasty fluid out on the ground and then put new fluid in the reservoir at the correct level when you are done.
if there is anything other than fresh, matching fluid in the system it needs to be overhauled. completely. bleeder is for air only. if the system has an 'immaculate clamping' issue it's time to red-tag the bike and get the system torn down and overhauled.
Are you saying that if a brake hose is damaged and causing the caliper to drag the entire system needs overhauled? If so I disagree. However if the system has been contaminated by oil and rubber parts are spongey then yes an overhaul is the answer but this was not mentioned. Bleeder is for air only... Really? What do you mean by that?
if im taking a line off? i'm going all in. esp if there was any damage. makes no sense not too. wont cost but another half hour or so to at least pull off the caliper and master and really hose it out, if not, replace all seals during a teardown. esp if it's a kids bike. may not be how everyone else does stuff but, it's how i do it. again, brakes i take extremely serious. if there is contamination in the system the system should be completely torn down and serviced P.A.N. period. the bleeder's primary function is for purging aireated fliud, not contaminants. at a min. all fluids shold be replaced per the OM. sooner if they been boiled. again- this is my approach to things and may not be how everyone else sees it and i respect others POV so...i wont say my way or the hiway. but that's how we do stuff at the motopad...sorry if i sounded too stringent.
The caliper seal is square lipped..and is designed to pull the caliper piston back slightly when the lever is released.... could be contamination...if it was me I would pop the pistons out clean them off real good....replace the seal and refill with fresh fluid you might also get away with just a good cleaning and some fresh fluid...your looking for dirt in and around the seal lip area dont sand the pistons off...they are coated KTM seal kits work if you cant find one for Husky..if you need parts
