2007 Caddy excessive brake travel

[BenT]

Hi all,

Well, it only took 3 months after I sold my Caddy before I got another one . This time being an SDI-flavour one. Ironically, it's got a braking issue...

If I brake hard enough for the ABS to activate (and the problem only occurs if the ABS activates, no matter how hard or gently I brake), the next time I push the brake pedal it travels a very long way before anything happens! The brakes work just as well as normal when they do engage though. I thought I'd fixed it when I replaced the unevenly worn front discs and pads and bled the hydraulic system, but apparently not. The brakes are normally very fierce and work well, it goes in a straight line under hard braking and the handbrake's working fine. No grabbing, either. None of the calipers are sticking and it's sailed through its MOT like it (I wasn't aware of the problem at the time).

After parking the van up for a while, or pushing the brake pedal a lot, it goes back to normal (until the ABS kicks in again). I haven't tried bleeding the ABS unit itself yet.

Has anyone encountered this before?

Thanks in advance

[BenT]

Oh, by the way!

It's not leaking fluid anywhere (the fluid level isn't dropping, anyway), no signs of any bulges on the brake hoses and the pedal doesn't sink to the floor on continuous depression. Thanks!

[STP]

It sounds like the abs block does have air in it and needs bled properly. There's an abs bleed function on most good diagnostic tools and VCDS can do it I'm sure but don't know the exact adaptation channel.

When the abs intervenes, it prevents you applying too much brake force by pushing back on the pedal and also reducing the pressure applied to the calipers of course but maybe your abs pump is pushing air into the line from the pedal to the block and that's what's making the pedal travel further.

[BenT]

Thanks for your reply! I think this is the most likely culprit so I'll give it a go. It looks like VCDS just activates the ABS system, then all you have to do is pump the brake pedal to dispel the fluid/air. The tricky bit is bleeding diagonally opposing calipers simultaneously without a ramp..

[BenT]

Update - the issue now appears to be resolved

I bit the bullet and bled the ABS unit with VCDS. Apparently it's not necessary to bleed the rear brakes as part of the process, and VCDS guides you through what you have to do. All very straightforward. I did the front brakes one at a time and it seems to have worked fine.

Having carried out a few emergency stops with the ABS kicking in, the problem hasn't recurred.

Hope this helps anyone with the same issue!