Help - creeping JK CRD brake pedal mystery. 2010 CRD JK

[rob8888]

Hi there

Had my JK CRD since new. I remember the brake pedal sunk a litlle way from new but brakes worked fine.

My jeep is now failing its annual certification as this pedal creep has become significant for them.

Now here's the odd stuff;
1) Lines have bleed several times - no air in system - certain.
2) When the engine is off the pedal is rock solid - pushing with 2 feet hard. Zero felt creep.
3) with engine running, the brakes are effective, but the pedal will slowly lower nearly to the floor. But pull vacuum hose off and pedal goes hard.
4) my highly experienced mechanic mate is scratching his head.
5) We checked inside the vacuum chamber - dry - no leaking brake fluid.
6) Spoke to an long experienced brake specialist and he said that the diesels have a problem with the vacuum pump being too strong and causes this. A google search suggests other people think this too, and infact someone reckons it's supposed to be like this for CRD's http://www.wranglerforum.com/f202/jk...r-1475569.html and http://www.lostjeeps.com/forum/phpBB...ca95f3#p238180
9. My problem is, that if it is an inherent issue, I'm going to have a hell of a job convincing the certifier.

So I've just ordered a new master cylinder as this seems like it can be the only problem (unless it has air somehow in the ABS - ABS triggers fine on gravel etc btw), and will switch it out when it arrives, but I suspect it ain't the issue.

Any collective knowledge here about the issue?

Many thanks in advance
Rob

[mick666]

My 07 CRD does the same thing. Stand on it as hard as you can and it slowly goes down most of the way but it does not hit the floor.
Has never been an issue in real time driving under any circumstance, mine is an auto. Find a different certifier!! Please post your end result when you replace all those parts!!
Cheers, Mick

[Classic Boy]

Have a look at the flexible brake hoses they may be ballooning under high pedal effort.

[Hoasco]

Same issue on my '07 CRD. Has no noticeable effect on brake performance driving or stationary. Pedal never hits the floor, always stops a bit up.

[RLT]

They all do it ... nothing wrong
Get your certification done at a Jeep dealership

[Johnboy]

My 09 rubi does the same thing but has gotten worse after a weekend of rocky climbs, spent almost 20 mins with all my strength holding on a 60 degree climb that went pearshaped till i could inch back and get nose back uphill without rolling after that went through several deep muddy crossings on way home stuff all brakes. stripped it today discs glazed and pads no better used orbital with 36 grit paper to remove burnt on mud and get back to bare steel again brandnew pads front and rear, brakes are much better but pedal feel mushy bled several times no air pulls up ok but wont lock up suspect that master is bypassing as can push through stroke till nearly hits floor.
Anyone had this experience?

[rob8888]

The outcome of this was that the certifying garage reluctantly approved it after I showed them comments from here, and was also backed up by a local brake specialist who said same, it's normal for the CRD's to have brake creep while not moving. They want me to get a written check from the aforementioned brake specialist before next year though. Sigh. Anyway, thanks for all your advice.