Jeep Ch'kee; poor/no brakes for first few seconds

[furoner]

Jeep Cherokee TD Auto. Brakes have been spongy for the last few months, if I pump the pedal really hard I can (it seems) bottom it, like metal on metal but it's all fine in normal driving conditions and situations.

Took it to a large franchise tyre/repair garage here (in Spain) but the guy who test drove it said there was nothing amiss.

Today I started the engine, out it into Drive, started forward down the track, braked and realised there was very little braking effect, more a gradual slowing down ! After a while of pumping, starting and braking, all returned to normal and I continued my journey. So what's happening? Hyrdo fluid res is full. Is this a failing servo - i.e a delay in the vacuum reaching required level? Or is this master cylinder rubbers failing? If it is the m/cylinder are replacement parts a DIY matter ? Pointers to a suppkier would be useful anyway. I have newish discs and shoes in the front and new shoes on the back.

I suppose my first course is to try another garage/work shop but would appreciate any input from anyone with experience. Cheers.

 

[Burnerman]

If fluid levels are ok then either the rear brakes are massively out of adjustment (drums only) or more likely the master cylinder is allowing fluid to pass back.
I can't recommend resealing these things, even if parts are available - a new dealer or pattern part is needed.
John

 

[Burnerman]

I should also have said - if you have had new rear brake shoes fitted recently, these MUST be adjusted right up to the drum. If they're not, the first push of the pedal moves the shoes into contact, and the next push actually does the braking.
The adjusters may be automatic (which seldom work as well as they should) or manual. I adjust the automatic types manually anyway after renewal - if that makes any sense!
John

 

[jctilingservices]

can you pump your pedal a few times and it gets hard ?

I am thinking that possibly the fluid is being pushed past the seal in the master cylinder as john mentioned

 

[furoner]

well......with engine off, the brake pedal is firm with some travel. With engine on and a long steady pressure, pedal eventually and slowly bottoms; if it is then pumped there is a wheezing sound with each pump and, again with each pump, the pedal works its way up in firmness to the top of its travel. Then again with a steady pressure it falls off....what smaybe termed 'creeps' I think.

Should a brake pedal creep in a diesel ?? Why?

 

[merlin50]

sounds like master cylinder is letting fluid pass back

 

[jctilingservices]

not a mechanic mate but heres a little tip i learned, get someone to pump the brake pedal up, clamp all 4 flexis ( 2 front and 2 back) see if pedal then drops, if not release the clamps 1 at a time, when pedal falls thats he wheel at which your problem lies.
If when all clamped the pedal drops its your master cylinder

 

[Burnerman]

As sure as eggs are little apples (?) this is a master cylinder fault.....happens from time to time, no difference between petrol or diesel.
If you're handy with the spanners you can bleed these from the top, where the brake pipes screw in.
John

 

[merlin50]

as its not loosing fluid it will be the master cylinder

 

[jctilingservices]

As sure as eggs are little apples (?) this is a master cylinder fault.....happens from time to time, no difference between petrol or diesel.
If you're handy with the spanners you can bleed these from the top, where the brake pipes screw in.
John

you talking about old fashioned back bleeding John ?

 

[jctilingservices]

as its not loosing fluid it will be the master cylinder

99% agree with you, but there is another option, that a flexi has colapsed

 

[Burnerman]

as its not loosing fluid it will be the master cylinder

99% agree with you, but there is another option, that a flexi has colapsed

Yep thats a good point...treading on the brake pedal while a marra feels for a swelling flexy
John

 

[Burnerman]

As sure as eggs are little apples (?) this is a master cylinder fault.....happens from time to time, no difference between petrol or diesel.
If you're handy with the spanners you can bleed these from the top, where the brake pipes screw in.
John

you talking about old fashioned back bleeding John ?

Aye, after years trying to fix old knackered Transits where the bleed nipples have long since snapped off, its worth risking the odd eyeful of fluid doing it this way.....also pushing back the pistons in the caliper when you think all is done just helps things along
John