Long story short, I was having issues with braking on my mk1 fabia VRS, pedal sometimes went to the floor with no breaking at all, if you let off and pumped the pedal, normal breaking continued. The master cylinder was replaced and a new fault has shown up, both front calipers are sticking badly, after 15 minutes of driving the brakes are fully on and it wont drive.

 

Has anyone seen this before or have replaced a master cylinder on one of these and have any advice? from what I gather the new master cylinder is not releasing any pressure on the front wheels, is it possible the new one is faulty or not the correct one?

 

Many thanks

Pop the vacuum off the servo and see what it does. The none return valve in the vac system can go faulty and jam the brakes on like you said. 

 

If you take the hose off altogether, you should be able to blow through it one way but not the other.b

tried that, seems to be working as intended, still having the same issue!

Something to be aware of. I had this problem many years ago on an old Vauxhall, and symptoms sound similar. Seals on the master cylinder were suspect, meaning that every time you applied brakes, fluid bypassed rear seals on master and fluid ended up in servo. Then drawn into engine and result was clout of white smoke. Test- apply brakes with vigour, then accelerate away checking for a white cloud in mirror.

On 11/08/2022 at 22:54, VWD said:

Something to be aware of. I had this problem many years ago on an old Vauxhall, and symptoms sound similar. Seals on the master cylinder were suspect, meaning that every time you applied brakes, fluid bypassed rear seals on master and fluid ended up in servo. Then drawn into engine and result was clout of white smoke. Test- apply brakes with vigour, then accelerate away checking for a white cloud in mirror.

Yes, I've had that in the past, too.

 

What can also happen is that the master cylinder seals/valving malfunction and stop letting fluid back through the cylinder and into the reservoir, stopping the fluid from returning from the caliper and holding the brakes on - giving the appearance of two sticking calipers.  It's not impossible that a brand new cylinder would have this defect straight out of the box.

 

I also had this happen on an old Fireblade I had, and the rubber gasket on the underside of the reservoir lid had became detached and traveled down the reservoir as the pedal was pushed and the fluid level dropped.  It, then, stopped the fluid level rising again, when the brake lever was pulled and the lever stayed at the bar and the front brake stayed on.  

100% it will be caused by the new master cylinder and/or its pushrod being outside of the manufacturers limits, basically the pushrod is too long and not allowing the piston to return once it warms up.

 

It may possibly be adjustable for length on your vehicle, if so then do that, otherwise try slackening the retaining bolts and inserting some C washers and resecuring, if that doesn't work then it could be a failed internal spring or pedal return spring (so much for my 100%) but I don't know the set up on your vehicle.

Do you know for sure that its only the front brakes that are remaining applied?

One other thing to look out for on cars that have adjustable servo rods is that some previous owner has "adjusted" the link, and the servo comes-in and holds on. After I had problems on the Vauxhall with a leaky master cylinder, I found I then had a linkage problem. In truth this was because someone had replaced the servo + master cylinder on a Victor 2000 with the servo and master cylinder from a Victor etc larger engine vehicle. But once I'd sorted out the servo problems ,this 2000 model stopped very well .

4 minutes ago, VWD said:

One other thing to look out for on cars that have adjustable servo rods is that some previous owner has "adjusted" the link, and the servo comes-in and holds on. After I had problems on the Vauxhall with a leaky master cylinder, I found I then had a linkage problem. In truth this was because someone had replaced the servo + master cylinder on a Victor 2000 with the servo and master cylinder from a Victor etc larger engine vehicle. But once I'd sorted out the servo problems ,this 2000 model stopped very well .

 

For readers under 60, the 2000 in this post is referring to the cubic capacity of the car, not its year of manufacture...😆

 

 

ETA - I'd forgotten how low down the filler flap was...

Edited 16 August, 20223 yr by gsmdo

gsmdo- the Vauxhall as in photo came in three flavors.One was a mild mannered 1600cc model. Then there was the 2000 cc model and last was the Ventura at possibly 3litre/3.5 litre. I owned a 2litre model, which had had the servo + master cylinder replaced from a Ventura. First problem was brake fluid leaking into servo from master cylinder seals. ( cue- white smoke from exhaust on braking, and loss of brake fluid ).

Next problem was "mal adjustment" of the servo linkage, which after replacement of master cylinder caused brakes to hold on.

On of the other problems on this last version of the Bedford power unit was the distributor ,which was mounted on top of the oil pump. Bad seals on the distributor /oil pump meant that the distributor could get oil flooded and cause ignition problems.

15 minutes ago, VWD said:

last was the Ventura at possibly 3litre/3.5 litre.

Actually 3.3l straight 6 on the FD.

Ventora.

 

In the nicest possible way suggestions for problems with modern vehicles from experiences with vehicles produced over 50 years ago are not particularly relevant, things like adjustable servo rods dissapeared 4 decades ago for cost savings, servos have been direct acting and integral with the master cylinder since then.

KEN/JR long time since I played /had to play with servo outputs. And again, I never actually had a Ventura of FD class, and Haynes Victor FD manual only mentioned 1600/2000 so my recollections are from lots of years ago. I only know of the Ventura AS  one previous owner could not tell the difference between the engine size./ car spec and fitted a few Ventura parts to the Victor. But a Victor 2000 married to a 1600 gearbox was something to worry the boy racers, but not good on fuel.

41 minutes ago, VWD said:

Haynes Victor FD manual only mentioned 1600/2000

Yeah, for FA through FD the Ventora was technically a different car to the Victor (inc 4/90).

Ken, pity one of previous owners did not know this, although an FD2000 fitted with a ventura servo+ master cylinder)properly adjusted)  and fitted with larger tread tyres stopped remarkably fast. And the performance in snow (with large tread tyres,and an arch or two full of snow) made it a remarkable vehicle. Like a tractor, with the engine power. Main problem on older models was the oil pump, mounted under the distributor where if the seals were poor, could mean a distributor with oil in/on points. I solved this with  a new oil pump and  a home built electronic ignition system, along with an engine rebuild.