# Master brake cylinder malfunction



## ladybirdmt (Jan 11, 2008)

The problem I posted in August re: losing power on highway as front brakes locking may be the master brake cylinder. Problem has been repeating at odd times. We stop, turn motor off, wait a minute, and restart- brakes release. Today on highway it happened again, and near shop where I had brakes/rotors replaced in April- what luck. We pulled in and mechanic checked front wheels, yes, indeed brakes locked up. Calipers were not seized. Very probably master brake cylinder malfunction. Has anyone else had MBCylinder need replacing on a 2005 XTrail? And... where can we buy a used cylinder? The mechanic called to check price, and was told 'must buy from a Nissan Dealer'. thanks for any help,


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## jdg (Aug 27, 2009)

Doesn't sound like a master cylinder to me, unless the vacuum booster is built into it as an integrated unit.
Sounds like it's time for a new vacuum booster (and a maybe new mechanic) since you say the front brakes release after shutting off the engine, thereby letting the stored vacuum bleed out of the booster.
Does this happen after you apply the brakes or 'by itself'?


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## ladybirdmt (Jan 11, 2008)

thanks for the reply. the xt is AT, so sometimes when put in 'D', the brake is at top (hard), other times,


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## ladybirdmt (Jan 11, 2008)

sorry, don't know why message was sent! Just now, I started xt, brake pedal was normal (allowed my foot pressure when depressed). other times, by the time I'm at end of driveway, brake pedal is hard (at top). the experience yesterday was: freewheeling down hwy at 90km, suddenly feel brakes on front wheels, xt deccelerates, then we stop engine, wait a min, start it up again, and sometimes, but not always, the brakes have released. If problem is possibly what you suggest, how do we determine whether the vacuum booster is integrated into MBcylinder, or separate? we don't have an estimate on cost of repair yet, so are just researching least costly way to repair. thanks, jeannie


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## jdg (Aug 27, 2009)

I'm guessing. I don't own an XTrail. The master cylinder will be bolted to the vacuum booster (big round tank).
Any decent mechanic should be able to tell you if the problem is the master cylinder or the booster.
If, as you say, the brakes apply themselves, without you touching the brake pedal, then I would say that the vacuum booster is the problem. A master cylinder just doesn't move by itself.
Unless you've got anti-lock brakes (and/or traction control) on that vehicle.
That opens up other possibilities too. Again, a decent mechanic should be able to figure it out straight away.


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## yorkie051 (Aug 16, 2014)

Try Ebay, I have just had a quick look and loads on there at reasonable price, £30 -£40, good luck.


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