weird braking problem

[troyhamilton]

My Jackal will come to a stop normaly then i have to break the front brake  line lose at the caliper to release  the brake. Is it the master cyl? rubber brake line or my caliper? previous owner told me of this happening to him. any ideas would be appreciated,

[normzone]

I'm not a brakes expert, and I don't even play one on television.

But one will be here shortly, so until they get here I will offer my opinion.

It's either the master cylinder or the caliper - you figured that out already.

You say you " break the front brake line loose at the caliper " - if I understand you correctly by doing so you're letting air into the system, and releasing the pressure the master cylinder built up.

I vote the caliper is sticking. But if I had brakes that treated me like that I'd rebuild / replace both parts, and you may as well do the hose while you're there.

There you have it - wisdom from the mouth of babes.  No, don't thank me, just diagnose my tail light / turn signals issue, and we can call it even.

 

[pete roper]

For whatever reason the piston in the master cylinder isn't able to return fully so the priming port to the reservoir isn't open. This means the braking system is effectively closed when the brake is released.

As the caliper heats up the fluid in the system expands. Since it can't escape back into the reservoir it's only choice is to push the pistons in the caliper out thus locking on the brake.

Find out why the piston can't return fully and fix it. There may be a small plunger from a barrel on the lever that is adjustable. I'll have to go and look at the one on my shitbox Cali to confirm.

Pete

[troyhamilton]

it done it when i rolled it out of the shop, maybe 10 ft back. no heat there. it hadnt been ridden all day, 65 degrees out side.

[pete roper]

It'll still be the return port. The fact releasing the pressure by cracking the bleed nipple or banjo bolt pretty much confirms it.

[Old Jock]

Well of course Pete is right

If you release the line and vent the pressure and the brakes loosen off, then its not the caliper, that is beahviing as it should

The fact you can brake at all, more or less tells you that the lines are fine that leaves the master holding the pressure on the system, so either the ports or the spring or a jammed seal I reckon

But my money is on the master

Go with Pete's idea first of course I'm an amateur and a not very competent one at that

John

[troyhamilton]

yep new fluid and maybe a new master cyl then.

[Huzo]

yep new fluid and maybe a new master cyl then.

Maybe the fluid hasn’t been changed since Christ died and has contaminated the bore of the m/c.
This could very well be contributing to the reluctance of the piston to fully retract and uncover the port.
The system cannot depressurise unless that port communicates between the reservoir and the piston.

[pete roper]

Troy, not necessarily. It may simply be an adjustment problem. I have to admit I can't remember what the actuation mechanism is, or even the M/C Setup on the Cali's. I see few of them nowadays as my work is almost exclusively CARC/8V.

I am though rebuilding my sidecar tug which will have the same, (Or very similar.) master cylinder. Let me have a Squizz at it and see if I can see what may be the issue. It maybe, really, very simple.(A bit like me.)

Pete

[troyhamilton]

thanks, i may get some brake cleaner and new fluid in the old beast.

[pete roper]

Don't think brake cleaner will fix it. Do you understand how a brake master cylinder works?

Pete

[troyhamilton]

kind of pete, ive never took one apart to be honest.

[Mike Tashjian]

The fluid is not returning and the Caliper releases when you crack the line.  Obvious it not the Caliper. The master cylinder piston gets pushed by the brake handle. If the brakes stay on either the M/C piston is not returning (stuck, bad return spring handle and not returning all the way) or the rubber hose has swelled from age and is blocking the return of fluid to the M/C.  I would remove the hose at the caliper and note how hard it is to move the brake handle. Fluid should drain out quite easily with almost no effort.  Mike

[troyhamilton]

brake handle works as normal.

[troyhamilton]

and it doest do it every time. just ocaisionaly. irritating in traffic to say the least. and it dont lock up all at once

[s1120]

So if it was a car....  I would say its the brake line. Ive seen them often on older cars..  The rubber breaks down and falls away from the outer cover and works like a one way check valve. Fluid under pressure goes down fine, but the rubber makes a flap that stops it from going back up after pressure is released..  Granted Ive not seen that often on motorcycles, and the master seems to be the much more common problem spot. Caliper is fine its releasing when you remove pressure.

[troyhamilton]

thats what my brother thought. his ford truck done this. gonna order a hose.

[s1120]

thats what my brother thought. his ford truck done this. gonna order a hose.

And really... it can never hurt to replace a hose.. they do go bad, and the bike is not a spring chicken any more...   

[troyhamilton]

nope not a spring chicken but i have a rubber chicken zip tied to the bike. the bike sat in a barn for 10 plus years...but was doing this before it was parked.

[Craig in Alabama]

Hi Folks,

This happened to me about 1/2 mile from the sellers house when I picked up my '98 V11EV. I released the pressure on that caliper with the bleed nipple and rode home using only the rear brake. Turned out to be a piece of crud in the master cylinder. A brake fluid flush solved the problem. I  was going to do that as a matter of course, so no big deal. Also on that ride home the left rear turn signal broke off and the charge system wasn't working. Glad I rescued the poor bike from the PO.

Cheers!
Craig

[johnk]

It could be an aftermarket/badly adjusted brake lever. If there's not enough free play it might not be allowing the master cylinder piston to clear the relief valve.

[D Knaus]

I have had this happen on pickup trucks, and once on the rear brake on my Norton (1975 Mk III with disc rear brake.)
It was the rubber brake line that had come apart on the inside and would not let the pressure off the caliper.
Try shaking the brake line when the brake is locked up, if it comes free it is probably the hose.
YMMV
-Dale