I've been having a few braking issues recently and trying to track down the issue. Over the last year (yes, its been gradual!) I've noticed the ABS become much more sensitive to starting, braking on any slight undulation seems to cause it to kick in, and that's where the problem starts:

Whilst the ABS is on, the braking capacity is REDUCED compared to cadence/threshold braking. But if I have pushed harder on the pedal whilst the ABS is on, then come off the pedal and back on again to try and brake without ABS, the pedal is much closer to the floor, and needs a lot more force for braking. This has only happened once or maybe twice this year, so wasn't really traceable to a problem rather than a one-off/freak chance.
But today it got serious, heading down a slip road to a roundabout, braked and then caught the tiniest of bumps and the ABS came on, NO brakes, came of the pedal and back on, still barely anything. Thankfully there was a nice grass patch with a gravel drainage ditch I could drive onto to slow down, if not it was going to be rear-ending a queue of cars at about 40 or 50mph .

Strange thing is there are no warning lights for ABS/brake issues. If there is anyone in the Norwich/Norfolk area who is able to do a VCDS scan for me to see if anything pops up itd be appreciated.
I'm hoping its not the ABS pump, purely because I don't have the money for a new one, or the turnaround time available for a repair kit! Might have to take chances on one from a scrappy.

One thing I do notice when the ABS does kick in, the rear is very loose, almost like its ever so slightly locked, whereas the front are at about half pressure or less. Not sure if that gives any clues either....

You could take out the fuse for the ABS for now to see if everything comes back to normal.

 

Then you know its something to do with the ABS system whether it be the pump/control module or possibly one of the sensors giving a dodgy reading maybe.

 

VCDS is a good shout to see if there are any codes and you can even monitor the sensors to see if something strange is going on

Happy to do a scan to see if there is anything obvious.

 

It sounds like the abs pump is just letting fluid through but if be surprised if this didn't cause a warning light or two...

 

What age is the car and has it had the fluid changed in the last two years?

Thanks for the ideas both!
@langers2k yeah it sounds that way but Id have expected some kind of warning too, maybe its just starting and I managed to 'push' it somehow
Fluid was changed about 2 years ago, though its barely ever used (I don't brake anywhere near as much as most people seem to ) and the car is an '55 plate with 217k on the clock Whereabouts are you Langers for a VCDS scan?feel free to PM rather than post out on here.. Drove the car again yesterday (glutton for punishment and danger!) and it seemed ok, but I was making sure I went very steady.
 

Sorry to jump on, but I've been having brake issues lately too.  Not quite as you describe in that the ABS is being too eager to kick in, but similar brake 'fade' issues.  If anything, I've thought that ABS isn't working as effectively as it should when test braking.

 

At first the problem was extremely intermittent, but when braked hard or pumped, brakes came back to normal and behaved for multiple long and short journeys.  Recently however it's been a permanent issue, where there is no feel to the pedal but when cadence braking stopping is fine.  Servo is definitely working, but it felt more like a master cylinder problem in terms of pedal feel and fade.

 

No obvious fault codes that I can find with Carista+OBD adapter.

 

My local indy mechanic has had a look at it today, checked the MC and says it's fine.  He's checking for vacuum leaks and VCDS faults, but if none what else could be at fault here?  Is this a sign of a faulty ABS pump?

 

Thanks!

Edited 6 December, 20187 yr by mrhappy

Right, dragging this one up from the dead
Life has been a bit crazy and busy so I haven't got any further with this, but now it is getting very bad. I'm now at the point where if the ABS kicks in, if I want any braking force, I have to pretty much kung-fu kick the brake pedal as hard as possible till I override the ABS and lock up a wheel, only THEN do the other brakes start to slow .
It seems replacement ABS pumps are silly money from skoda, but refurbs (IE: the cheap option I can afford) have a 2 week turnaround....but I need the car daily without letup. Would swapping it over to a 2nd hand one work? Or do they need to be specific models or coded to the car?

1 minute ago, robt100 said:

Right, dragging this one up from the dead
Life has been a bit crazy and busy so I haven't got any further with this, but now it is getting very bad. I'm now at the point where if the ABS kicks in, if I want any braking force, I have to pretty much kung-fu kick the brake pedal as hard as possible till I override the ABS and lock up a wheel, only THEN do the other brakes start to slow .
It seems replacement ABS pumps are silly money from skoda, but refurbs (IE: the cheap option I can afford) have a 2 week turnaround....but I need the car daily without letup. Would swapping it over to a 2nd hand one work? Or do they need to be specific models or coded to the car?

where are you located?

Before you replace anything get a scan done so you know what your coding is and what one you should look for

 

I fitted a used one from ebay without any issue (upgrade, not due to failure)

1 minute ago, Eddie-NL said:

where are you located?

Before you replace anything get a scan done so you know what your coding is and what one you should look for

 

I fitted a used one from ebay without any issue (upgrade, not due to failure)

I'm about 30mins west of you Eddie.... You've worked on the car before . About 5 miles south of Norwich..... Would you be available for a scan?? (I mean, to scan the car, not me scan you)

There are no ABS/brake warning lights popping up at all, so it THINKS its working ok. But I'm getting to the point where I'm scared to brake on any undulating surface, as it seems to go off on the slightest bump or hint that there might be stones/gravel within 100 yards

Right, bit of an update. I've been to see Eddie-NL and everything checks out ok with the ABS pump and speed sensors on VCDS. I've also recently had new discs and pads fitted which has made the pedal a little firmer and more 'bite'.

What I did notice the other day though with the cold mornings we have had the last couple of days, is that for the first pedal press the pedal is firm and as it should be, but as the heatsoak from the engine starts the pedal goes soft again. With a higher ambient temperature (15-20degrees) the pedal is soft, but not below 10....

Could this maybe be a seal in the M/C? And with the minor heat expansion of the metal is letting fluid past the piston? Or something totally different and just a strange coincidence?