Hi

2006 Fabia vRS

Had the master cylinder replaced a couple of weeks ago. Brakes much improved.

However, a couple of times since the brakes have stuck on. Apply brakes for example on approach to roundabout. Go to accelerate away from roundabout and car is held back. When you take your foot off the accelerator it feels like the brakes are on.

Pulled over when safe and you could smell hot brakes. All 4 wheels were hot so brakes definitely sticking.

Turned off, waited a few minutes then all ok again.

It's happened 3 times now.

Car going back to garage tomorrow but mechanic has said he's not come across this before. We've used same garage for several years now.

Any ideas?

Mark

Hi Mark. All four sticking at once, only after a few minutes of braking, and freeing off once it has cooled down, points at the master cylinder not letting fluid back to the reservoir rather than at the calipers. Four calipers don't all seize at the same time, and the timing (straight after the master cylinder job) is a strong clue.

How it works: when you let the pedal go, the piston in the master cylinder returns fully and uncovers a small return port to the reservoir. If the piston is held even slightly forward, that port stays covered. As the fluid warms up from braking it expands, has nowhere to go, and pushes all four brakes on. Leave it a few minutes, it cools and contracts, and everything is fine again. That matches what you're describing.

Things I'd ask the garage to check tomorrow:

1. Pedal return. With the engine off, make sure the pedal comes all the way back to its stop and isn't being held by the brake light switch, the trim or the carpet. If the brake lights stay faintly on or flicker with your foot off, the pedal isn't fully home.

2. Servo pushrod to master cylinder clearance. If the new master cylinder sits differently on the servo, or the pushrod is now pressing on the piston with no free play, you get exactly this. There should be a small amount of free play before the piston starts moving.

3. The part itself. Is it the correct master cylinder for the vRS, and is it new or reconditioned? A wrong-spec or faulty unit with a sticking piston can do the same thing.

4. Fluid. Make sure it was topped up with the correct DOT 4 type and nothing else went in.

A useful test if it happens again with the garage: when it's stuck, safely crack a bleed nipple open. If fluid spurts out under pressure and that wheel frees straight away, the pressure is being held upstream (master cylinder or servo side), which confirms it.

Please don't keep driving it like this, as dragging brakes overheat quickly and can fade. Hope it's an easy fix, let us know what they find.

Thanks - I'll be sure to mention these things to the garage tomorrow

Time to find a new garage I think 🤔

He was able to reproduce the problem which I guess is the only bit of good news.

His view is that for some reason the master cylinder is not releasing pressure when the pedal is released. Yep, don't need to be a genius to work that out.

When he changed the master cylinder he wasn't able to source an original so used a pattern part. He said previously he's only ever used original parts when changing master cylinders. His thought is that the new master cylinder is slightly out of tolerance and is not releasing pressure.

His advice is that I should try to source a second hand original part and he will fit it.

Don't want to do this as the second hand part could quite easily be no better than the original one that was on the car.

Quite disappointed with his attitude as have used his garage for a number of years.

Anyway, have got the car back home and booked into a local Skoda specialist. I explained what had happened and they were quite happy to have a look. Perhaps they'll have a new customer in the future.