Pulsating Brake Pedal

[Polecalex]

Hi All,

I recently changed my brake pads on my 2015 Cupra Leon MK3 for an MOT as a few of the inner pads were running quite low. As this was a rushed job I didn't change my discs or bleed the system as I just needed it to pass the MOT.

Since the change, the brake pedal has been pulsating no matter the speed I'm traveling at. It feels like my ABS is engaging however there are no lights on my dash and the wheels aren't locking up. It feels like something is pushing back like there is a high point on the disc?

I'm changing the discs and bleeding the system today but just wanted to ask if anyone else has seen something like this before? If it doesn't solve it, I'll be going to a garage but I'm hopeful it will.

In a side note, I've not bled the clutch on this car before so I'm not too certain where the clutch bleeder nipple is, has anyone got any pictures or a description before I go on an engine bay adventure.

 

[RUM4MO]

From your description of why you needed to replace the brake pads, it sounds a lot like the unseen inner face of some of the discs has progressively corroded and these new pads have still to get ripped down to "shape" to suit that - though, there could be the extra problem that the corroded probably outer, areas of a/some discs, are not generating much friction so the chances of these new pads ending up actually contacting the remaining, if there is any "clean" areas are low.

Sounds like new discs must be fitted to quickly solve this problem - and allow the new pads to survive and do their job, plus allowing for an MOT pass, at least as far as the brakes are concerned.

Edit:- I'd be willing to give the clutch fluid change a miss, and just change the brake section of the fluid lines.

 

[Polecalex]

From your description of why you needed to replace the brake pads, it sounds a lot like the unseen inner face of some of the discs has progressively corroded and these new pads have still to get ripped down to "shape" to suit that - though, there could be the extra problem that the corroded probably outer, areas of a/some discs, are not generating much friction so the chances of these new pads ending up actually contacting the remaining, if there is any "clean" areas are low.

Sounds like new discs must be fitted to quickly solve this problem - and allow the new pads to survive and do their job, plus allowing for an MOT pass, at least as far as the brakes are concerned.

Edit:- I'd be willing to give the clutch fluid change a miss, and just change the brake section of the fluid lines.

Thanks for your reply, that's what I thought might be the case. I've hardly driven it like this so the pads will not have worn into shape. I'm going to go ahead with changing the discs and bleeding the brakes.

I thought about missing the clutch however it's well overdue a brake fluid change anyway as it's pretty much black now and my clutch pedal is definitely degrading so I thought I'd give it ago and try solve two problems in one

 

[Mr Pig]

The simplest possibility as that some crap got caught behind the disk and it's not running true. If that was case I'd also expect to feel a slight vibration through the steering wheel at speed but you might not.

There is a valve on top of the clutch line. I'm not sure if it's for a fluid change but you'll get most of the fluid out if you bleed the line there. The little plastic restriction block is in there on the Cupra and if you remove it the clutch is a heck of a lot nicer!

 

[Polecalex]

The simplest possibility as that some crap got caught behind the disk and it's not running true. If that was case I'd also expect to feel a slight vibration through the steering wheel at speed but you might not.

There is a valve on top of the clutch line. I'm not sure if it's for a fluid change but you'll get most of the fluid out if you bleed the line there. The little plastic restriction block is in there on the Cupra and if you remove it the clutch is a heck of a lot nicer!

I've had the front discs off and there is a high point, changed over with the new discs and it's sorted the issue. Problem I'm having now is that the rear caliper bolt is seized so I can't get the new discs on

In regards to the clutch, when I bleed them I think I've found the bleed nipple, I'm assuming it's this in the picture?

 

[Mr Pig]

Yes, that's the valve. Be aware that it is plastic.

 

[SuperV8]

I've had the front discs off and there is a high point, changed over with the new discs and it's sorted the issue. Problem I'm having now is that the rear caliper bolt is seized so I can't get the new discs on

Which bolts are seized?
The large M12 triple square caliper carrier bolts? or the smaller caliper slider bolts?

If the triple square bolts - ensure you clear out all the junk/rust out of the centre and give the tool a tap with the hammer to ensure its fully seated - assuming you have the correct size triple square tool?
They are tight - 90nm + 90deg - so you would need a breaker bar to remove, which can be tricky to get access of a floor jack.

On some versions you can change the rear discs without removing the caliper carrier - you can just maneuver the disc under the carrier.

Whenever you are fitting new discs it is critical to ensure the hub is spotless. I use a small needle files to carefully scrape any rust away, and a rotary wire brush in my drill.