Rear brake pedal frozen

[Derek]

A few months ago I was taking my s10 out for a ride and noticed that my ABS light came on. I shut the bike down and started it again and the light went off and stayed off. But a week or so later I noticed it came on again, but this time the rear brake pedal was hard a rock and wouldn't depress. I took it home to have a closer look, but wasn't able to do so immediately. Eventually after reading through the forum for similar problems the most common solution was to bleed the brakes, and flush the fluid, and cycle the ABS system.

However, no matter what I do, the rear caliper will not bleed and the pedal stays frozen. After going through the service manual, the only description I could find that might be helpful was that if water makes its way into the ABS unit that it can cause vapor lock. I thought to try bleeding the lines directly on the ABS unit itself. I found the line connected to the rear brake and bled just a little fluid out and it seemed that the pedal moved in response. But that didn't solve the problem.

I'm left with maybe removing the whole ABS unit, cleaning it out and reinstalling to see if that clears it up. I'm worried that the unit needs to be replaced and that's a pricey part. I've cycled the ABS at least a dozen times and get no feel through the pedal when the rear cycles. The front brake seems fine. Any thoughts?

 

[Derek]

By the way, just to rule out the rear master cylinder, I loosened the hose going from the top of it to the ABS unit and the master cylinder works and the pedal moves freely. So I'm fairly certain it's not the master cylinder. Also, when everything is connected the rear caliper never closes either, so the pressure keeping the pedal hard is clearly coming from the ABS unit.

 

[~TABASCO~]

Just a few suggestions to check......

The bolt holding the pedal to the frame, make sure that is lubed and attached properly..

Take the rear caliper off like you would be changing the pads. Take a large C clamp and push the piston in. Make sure the out side of the piston is clean. If it goes in smooth, then push the rear pedal and make sure the piston is then coming back out. If the piston is stuck, I would suggest pulling the piston and carefully looking at the two rubber seals. Make sure one has not "rolled over"..... (I had this happen to one of my front calipers on my 2012 when the bike was brand new, I found the issue, and Yamaha replaced the rubber seals)

If after all that is "good" and checks out perfect and you still have a problem, let me know.... We can go on to plan "D-E-F-G"


By the way, what year is your bike? How often do you change the fluid? When was the last time the fluid was changed?

 

[gunslinger_006]

Subscribed. This is interesting.

My advice is to bisect the problem as you have to try and test each part in isolation: master cylinder, abs, caliper+piston, lines.


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[Derek]

Tabasco,
I have a 2012. I bought it last year and have never done the fluids on it. So I don't know.

I took the rear caliper off and the piston was stuck all the way in. I took off the fluid line and put a screwdriver down in the hole and pushed the piston out enough to grab it and pull it out. It was essentially stuck. The rubber seals looked pristine. I worked the piston until it loosened a bit, filled it with fluid and put it back on. But trying to bleed the system still will not bleed. The pedal is still too hard and is not working the piston at all. This is why I suspected the vapor lock in the ABS unit.

 

[Derek]

gunslinger_006, that's essentially what I've been trying to do. Everything is pointing me to the ABS pump unit. Removing the top line from the master cylinder frees up everything from the master cylinder to the caliper. Loosening the line at the ABS also lets the pedal move. The ABS unit is the only thing left.

 

[~TABASCO~]

Tabasco,
I have a 2012. I bought it last year and have never done the fluids on it. So I don't know.

I took the rear caliper off and the piston was stuck all the way in. I took off the fluid line and put a screwdriver down in the hole and pushed the piston out enough to grab it and pull it out. It was essentially stuck. The rubber seals looked pristine. I worked the piston until it loosened a bit, filled it with fluid and put it back on. But trying to bleed the system still will not bleed. The pedal is still too hard and is not working the piston at all. This is why I suspected the vapor lock in the ABS unit.

I have more ideas, I can talk about them over the forum for others to learn. But we might cover a lot more ground over the phone. If you like PM your number.

I recently worked on a Tenere that was a 12 that had black brake fluid and a ton of water in the system.
You said the rear brake piston moves freely now in and out? And even with the caliper removed the brake pedal is not working ‘seized’? You have pulled the mounting bolt to make there is lube on this bolt. I recently removed one that when I removed it “smoke- dirt smoke” came from it. I could see as I pushed it down the spring was not strong enough to pull it all the way back. It was just jamming.

 

[gunslinger_006]

Man. That pic is terrible. I flush my brakes once a year but this makes me want to do it twice lol.


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[~TABASCO~]

Man. That pic is terrible. I flush my brakes once a year but this makes me want to do it twice lol.


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IMOP- once a year minimum !
I see so much crazy crap that just a little TLC would have prevented !

 

[Sierra1]

My kid told me last year that his brake pedal wasn't working. He brought it over. . . . nothing wrong, but a bolt that looked like that. No lube, and plenty of crud. After some blood, sweat, and tears, pedal worked perfectly. You're right. . . . minor things can turn into major things if you're not careful.

 

[Don in Lodi]

Exactly my issue. I bypassed the rear brake circuit of the abs unit. I have rear brakes again, no muscle memory for it though, 90,000 miles of linked brakes and all. Still have the abs light though. I can't figure out our code stuff. Way to many numbers come up on my screen, I have no idea what I'm seeing, let alone clearing them. I'm bummed. I can't afford the replacement costs to make it all right again. You know, abs units are not supposed to fail with a disabled brake scenario, fail, sure, but not making the vehicle unsafe. Pisses me off a bit.

 

[yoyo]

I had a similar issue with the pedal mounting bolt, it wasn't seized but I had a look and it was completely dry, trouble I had was thinking if the bolt is like that what are the suspension pivots like, 2hrs later the swing arm was off and the drive shaft out. Feel better for doing it though.

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[patrickg450]

Exactly my issue. I bypassed the rear brake circuit of the abs unit. I have rear brakes again, no muscle memory for it though, 90,000 miles of linked brakes and all. Still have the abs light though. I can't figure out our code stuff. Way to many numbers come up on my screen, I have no idea what I'm seeing, let alone clearing them. I'm bummed. I can't afford the replacement costs to make it all right again. You know, abs units are not supposed to fail with a disabled brake scenario, fail, sure, but not making the vehicle unsafe. Pisses me off a bit.

report that shit, YNA will NEVER address the issue if no one complains. I made the purchase of a new ABS unit for my piece of mind and I dont see the need to buy a new ST.

Report that shit, ask Uncle Bob about it.

 

[WJBertrand]

This thread had me checking my brake lever pivot. I’ve lubed the shifter pivot a couple times but never looked the brake pedal until today. It seemed to be working alright but it’s been 78K miles of road, rain, dirt, dust and mud after all.
There was not a lot of crud in there but what looked like some black aluminum dust. The wearing surfaces looked scored too. Clearly wear debris and no evidence of any kind of lubrication at all. Dry as a bone. I cleaned it all up and liberally applied some wheel bearing grease. I made sure to fill the grooves on the pivot pin which I believe are intended as grease reservoirs if you will. Feels nice and smooth now.


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[gunslinger_006]

This thread had me checking my brake lever pivot. I’ve lubed the shifter pivot a couple times but never looked the brake pedal until today. It seemed to be working alright but it’s been 78K miles of road, rain, dirt, dust and mud after all.
There was not a lot of crud in there but what looked like some black aluminum dust. The wearing surfaces looked scored too. Clearly wear debris and no evidence of any kind of lubrication at all. Dry as a bone. I cleaned it all up and liberally applied some wheel bearing grease. I made sure to fill the grooves on the pivot pin which I believe are intended as grease reservoirs if you will. Feels nice and smooth now.


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I am going to do the same tonight.

Ill post pics of what i find.


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[Edbo1960]

Lithium grease do the trick?

 

[WJBertrand]

Lithium grease do the trick?

Should be fine. Anything would be better than what I found, or more accurately, did not find.


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[gunslinger_006]

I pulled both sides apart, to find the shift side had ages old grease that had solidified. The brake side had a wisp of old grease, not even enough to harden.

I cleaned and greased everything fully and reassembled both sides. Feels great now (felt good before).

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[Derek]

Sorry for the delay in getting back to this, but I was kept pretty busy over the holiday. So I finally got back to checking the pivot, and my bike is fairly pristine. The previous owner said he never took it offroad and it was garage kept and it looks it. I've pretty much done the same so far. I've been on a couple camping trips down some dirt roads, but nothing muddy. As you can see from the pics everything is clean enough to eat off of.

I was very skeptical that this would be the problem, since releasing the upper hose of the master cylinder released the pressure in the line and the brake pedal would move freely. So it was not bound at all. But when I put the pivot back in I pressed the pedal and it was hard still. But then I pressed it again and something broke loose and now it depresses all the way. I'm stumped. I have no explanation.

But my battery is low so I can't cycle the ABS. I put it on a charger and will try to cycle it and finish bleeding it later. Hopefully this is all good now. Thanks everyone for the input.

 

[Nikolajsen]

Fingers crossed