Brake problem - MVAgusta.net
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post #1 of 27 (permalink) Old 03-11-2012, 10:25 AM Thread Starter
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Brake problem

Hi,

I have a serious problem with my brakes. I have a 2005 F4 1000S.

Today I went for a short ride after winter hibernation. Meaning that I haven't ridden the bike for almost 6 months.

The bike start up normally and everything felt normal. But then after aprox 3 miles the front brakes started to behave weird. When I used the brakes the brakes would let go after I had stopped breaking. Causing a total lock-up of the front wheel.

The master break cylinder was completely jammed. Meaning the break lever was in the most outward position and I couldn't squeeze them even for a tinny bit.

So there I was in the middle of the road and I couldn't even move my bike. I called my friend to bring me some tools. By the time she got to me (10-15min) the brakes let go a bit (they were still grabbing a little bit) so I at least could drag the bike away from the middle of the road.

Then I wanted to release the pressure inside the brakes by unscrewing the bleeding nipples on the calipers. A few drops of brake fluid came out.

Then I drove the bike without using my brakes back home. Now the bike is in my garage and I don't know what to do?

By now the calipers have completely let go and the wheel is free to move.

I am not an expert when it comes to brakes and mechanical stuff. But in my opinion the master brake cylinder jammed up and after squeezing the lever and it didn't release the pressure in the hoses as it should.

So any thoughts? Advice? Anyone also had problems with their master cylinders ?

Thanks

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post #2 of 27 (permalink) Old 03-11-2012, 11:21 AM
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This is a new one on me...

Have you changed the fluid??

5.1 brake fluids good to use and should ideally be changed each year anyway

Flush the system, replace with new fluid and see how that goes-

While your at it check the prisons in the calipers too, just incase they're binding- its my guess they'll be fine and the issues some damp in the lines / fluid and it's contaminated your fluid which could of got extremely hot under use, expanded and locked the pressure up-

Let us hear the results- ideally you'll see some milky fluid in the lines when flushing then it's problem sorted

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post #3 of 27 (permalink) Old 03-11-2012, 11:31 AM
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James may be on to it as water in the lines will boil under pressure and expand in the lines forcing the pads onto the discs...

But I would service the brakes thoroughly. Check your brake pads for wear. If they are worn down then the pistons may be coming out a long way when you apply the lever. If then you have dirt / corrosion on the exposed areas of the caliper pistons then your brakes may not back off after applying pressure as you would want them too.

So I would take off the calipers, check the brake pad wear, clean the caliper pistons where they are exposed and then massage them in and out using common sense and a bit of plywood or similar to prevent the pistons popping out of their bores.

I would then fit new pads if needed and push the pistons back. I'd then refit the calipers and bleed the system to fill with fresh fluid.

If you still have a problem you need to check the master cylinder for correct operation.

My instincts point to the calipers..or as James says water/contamination in the hydraulic fluid.

I hope you sort it out ,

joe

Last edited by gotojoe; 03-11-2012 at 11:34 AM.
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post #4 of 27 (permalink) Old 03-11-2012, 11:34 AM Thread Starter
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Hi James,

thx on the input.

I've changed the Break fluid exactly 1 year ago. I do that each year.

I'm scheduled to do maintenance on my bike this week, so I'll fully investigate what you've just mentioned.

But I didn't noticed any extra heat on the brakes at all. I checked by hand when it happend.

Is there a way the reason for the malfunction is the seal system in the master cylinder? I haven't seen the inside of a one.

I'm afraid that a similar malfunction occurs again. When it comes to brakes I want to be 100% sure.

So little time, so much to do. (Churchill)

Don't forget to live your dreams !!!
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post #5 of 27 (permalink) Old 03-11-2012, 11:38 AM Thread Starter
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Thanks Joe,

I've just bought a new set of brake pads. So I planed to change them anyway.

But the pads are not worn too much. They still have around 40% left in them. And the bike has 18.000 km ...

So little time, so much to do. (Churchill)

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post #6 of 27 (permalink) Old 03-11-2012, 11:42 AM
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Water.
He said he had not ridden it for 6mths. B fluid is highly absorbent and some water may have been absorbed into his system during the inactivity.
He said after he rode a little, Lock up happened. The water heated up and expanded.
Then he said after he left it for a while he was able to move the lever a little. The water cooled and condensed again.
The reason I dont believe it is a stuck caliper is because he says it releases after being left alone.
Recommendation, full flush of the system.

That is what I belive and what I would do, but you may wanna check with Knurl, he would problaby have more knowledge on this......... and he's old. Old guys know alot of stuff :-) hahahah

Tree
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post #7 of 27 (permalink) Old 03-11-2012, 11:49 AM
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Well ..He needs to fully service his front brake system as whatever is causing it is what it is ...

If the pads were jamming onto the disc then the heat would cause expansion down there and then back off as the disc and pads cool..Who knows..He needs to get the wrenches out and have a look see.

Tree is right on the brake fluid tho and a point to bear in mind with Dot 5.1 is that it has a higher WBP but is also more hygroscopic than Dot 4.0. So therefore James is on the the button with his policy if changing it once a year.

I think the race guys change it out much more frequently !

joe

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post #8 of 27 (permalink) Old 03-11-2012, 12:29 PM
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Have never had it happen on a bike but have had these exact symptoms in cars and pickups when there was air in the system.

Toby

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post #9 of 27 (permalink) Old 03-11-2012, 02:16 PM
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Thumbs down locked?

its the piston in the M/C, something isn't letting it return to the at rest position and opening the return port allowing the pistons to retract.
moisture/water won't do it, but a piece of dirt could in theory block the return port

make sure the brake switch is correctly mounted
check the adjustment of the brake lever adjuster. is it ALL the way out? (for you guys with big hands)
mine will just start to move the piston when adjusted all the way out

people have this trouble all the time with the rears

when playing with the push rod or changing footpegs/levers

Brembo radial front M/Cs have an adjustable pushrod that will cause the problem too

flush the system 1st

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post #10 of 27 (permalink) Old 03-11-2012, 02:33 PM
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[quote=MvMerito;510570]

While your at it check the prisons in the calipers too,

Prisons allways have lockups. lol


Someone once asked me if I was "out of my mind". To which I replied "of course I am, as its dark & scary in their".
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