Signs of Brake Master Cylinder Failing.....

[Kedge]

Just after some as advise regarding what I think might be a failing brake master cylinder. It's the only part of the system that hasn't been replaced in the process of upgrading to WMS brake and a Clio servo.

On the way to the MOT the other week it felt like the brakes were starting to bind a little but we're then fine for the MOT and since, in that regard. Then last week on the way back from having the wheel alignment done I started to get somekind of knocking feel through the pedal.

I'd not had chance to look it over until yesterday, when I found a puddle under the car, felt very much like brake fluids so I got under the car to try and see where it was coming from. I found a couple of runs off the gearbox but clutch save was fine, I then found runs off the bottom of the servo but nothing down the face of it from where the master cylinder mounts to the face of the servo so it looks like it's leaked out from the servo.


So would consensus be that the master cylinder is dying?

Cheers
Dave

[daimlerman]

It's a very fine balance to get the spacer correct between the master cylinder and the Clio servo.
I seem to remember that I buggered at least one master before I got it right...
Fortunately my local GSF were very understanding regarding the buggered master!

If the spacer is too long,the brakes will bind,the fluid overheats and locks the brakes on,slacking off the m/s mounting bolts to the servo will get you home,then you need to fiddle about making a shorter spacer.

[Kedge]

Il they only felt like they were binding once and that was only for a couple of miles, has done quite a few miles since without the binding.

My question is does all the above sounds like the MC is on the way out?

[daimlerman]

Il they only felt like they were binding once and that was only for a couple of miles, has done quite a few miles since without the binding.

My question is does all the above sounds like the MC is on the way out?

If the spacer is not just right,it will cause m/c failure...

Hence my post!

[Kos]

I had binding brake dramas on the e24, we changed everything including the linkage bushes and it was found to be a sticking MS

The MS is always overlooked and most are at the point where they probably will need changing

[Kedge]

I see what you're saying Malc, but it was only a very mild bind for a few mins that hasn't returned, my understanding from others than have had spacer issues its left their cars with the brakes stuck solid, especially with the WMS brakes.

I'm thinking the fact the cars only done a few miles in the last 5 and a bit years and it's an '86 car the seals may well be perished, afterall the same has happened with two fuel pumps before buying new.

Would the strange pedal feel point to a MC issue though?

[Demlotcrew]

I would wipe whats there, take it for a drive, or with the engine idling press hard on the brake pedal for a few minutes and check again. Its highly unlikely its leaking internally and coming out the servo join.

[Kedge]

Cheers Andrew, I'll girve that a go. Just got off the phone to Matt at ECP and it looks like it might be hardwork to source a new one anyway any idea what could cause the strange pedal bump feel and knocking feel?

What's the difference between an ABS and non-ABS MC?

[Brianmoooore]

What's the difference between an ABS and non-ABS MC?

Nothing internally. The non ABS cylinder has two ports for the front brakes, while the ABS cylinder has just one port, with the second being blanked off either by a screwed plug or by simply not being drilled and machined.

[daimlerman]

M/C is the same between ABS and non ABS IIRC,it's the way it's piped that is different.

Non-ABS cars use the port on the underside,ABS cars have this one blanked off.

I bought my last one from GSF,but it was three or four years back,now.

[Bristol_Jer]

My local GSF had one in stock last month, cost me about £60 I think it was. I put a Clio servo on mine same time as the new master cylinder and made my spacer too long, had to trim it off and been fine since. I'm running WMS brakes too.

In my opinion, if you've any doubt about the master cylinder then change it, it's not a lot of money for piece of mind.

[Kedge]

What's the difference between an ABS and non-ABS MC?

Nothing internally. The non ABS cylinder has two ports for the front brakes, while the ABS cylinder has just one port, with the second being blanked off either by a screwed plug or by simply not being drilled and machined.

Awesome, cheers Brian.

[Kedge]

Had a short drive today, cleaned up everything underneath and covered it all in talc and there's been no sign of leaks. However you can hear air in the system when I press the pedal and the pedal is spongy.

[BenHar]

Hiss of air is normal. That's the servo working.

Spongy implies that the brakes need bleeding.

Ben

[Kedge]

spongy pedal has only just happened since last being driven, since it's lost the fluid mentioned earlier in the thread.