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[2cvandy]

"The brake fluid has expanded and put the brake on"

What ?? !!

As has already been said ;

there are two possibilities ;

1. The pistons have become stuck and not retracted, in which case you need to strip and clean the caliper (unlikely IMHO on a relatively new bike unless it's been out in some particularly foul weather). or 2. the pads have rusted to the disc through moisture in the atmosphere or the disc being wet when the bike was parked. In which case a whack with a lump wood or an application of throttle should free them.

[2cvandy]

"The brake fluid has expanded and put the brake on"

What ?? !!

As has already been said ;

there are two possibilities ;

1. The pistons have become stuck and not retracted, in which case you need to strip and clean the caliper (unlikely IMHO on a relatively new bike unless it's been out in some particularly foul weather). or 2. the pads have rusted to the disc through moisture in the atmosphere or the disc being wet when the bike was parked. In which case a whack with a lump wood or an application of throttle should free them.

[2cvandy]

"The brake fluid has expanded and put the brake on"

What ?? !!

As has already been said ;

there are two possibilities ;

1. The pistons have become stuck and not retracted, in which case you need to strip and clean the caliper (unlikely IMHO on a relatively new bike unless it's been out in some particularly foul weather). or 2. the pads have rusted to the disc through moisture in the atmosphere or the disc being wet when the bike was parked. In which case a whack with a lump wood or an application of throttle should free them.

[2cvandy]

"The brake fluid has expanded and put the brake on"

What ?? !!

As has already been said ;

there are two possibilities ;

1. The pistons have become stuck and not retracted, in which case you need to strip and clean the caliper (unlikely IMHO on a relatively new bike unless it's been out in some particularly foul weather). or 2. the pads have rusted to the disc through moisture in the atmosphere or the disc being wet when the bike was parked. In which case a whack with a lump wood or an application of throttle should free them.

[2cvandy]

Apologies for the repeated posts, no idea what happened there, except t'internet went off and recovered as I was posting,,,,, perhaps it has a stutter?

[jefrs]

I've had the fluid expand more than enough times on vehicles to know that this happens, especially if the machine has been left standing. The brakes come on hard, very hard, and the only way to free them off is to bleed some fluid out. Then the caliper can retract the pads and the brakes free off. The roadside fix is simply to let some fluid out. There may be air in the system and the fluid can squirt out with some force. Bashing the caliper is a good way to break it. Easy does it, relieve the pressure in the pistons first.


Bottle of new DOT.4, Phillips screwdriver, 8mm spanner, some clear tubing and a jam-jar, and the time it takes to drink a cup of tea, if that. I also use a 35ml plastic syringe, because it's less messy filling the reservoir than spilling brake fluid over the tank.

[Dennis C]

IF the fluid were to expand it would just go up the pipe into the resovoir as it does when it expands due to heat otherwise the brake would become it's own master, Either the pads have corroded to the disk or the calliper pistons are corroded and stuck.

[Scalyback]

2CVAndy, there you are. you still on the bikers club france forum?

[2cvandy]

oui, bien sur,,,,,,,,,

[PeteF]

There would need to be something very wrong with the master cylinder to allow any expansion of the fluid to affect the slave cylinder. When the actuation lever is released the fluid if free to return to the reservoir. If that wasn't the case then the pressure would be permanently in the system and the brakes would be on all the time. I suppose this could happen if the reservoir vent were blocked but.......
The real danger of using old water-contaminated brake fluid is that it lowers the boiling point of the fluid which can render the brake useless under hard braking.