Hi folks
My ZX has always had what I consider to be excessive free travel on the brake pedal. I have made the following checks and observations:
Rear brake linings are OK and self adjusters work fine, leaving 10mm of thread to go on both sides.
The brake pedal moves completely freely for about 3 inches before I can feel it contact anything (master cyl piston, I presume)
I have bled the brakes after replacing rear pipe
Stopping power is excellent
According to the Haynes BOL, you adjust the clevis on the servo pushrod to give a certain projection, then adjust the end of the pushrod where it operates the m/cyl
<b>Questiom</b>
I do not really want to remove the m/cyl or servo, so can (and should) I adjust the clevis by taking out the pin that attaches it to the pedal, slackening the locknut and unscrewing it to take up some of the clearance? I appreciate that no free travel will cause brakes to bind!
Incidentally, other than Haynes, is there any decent literature available? Russek only seems to be for petrol models.
ZX master cyl/servo question
Moderator: RichardW
Mike,
Have we talked of this before? Drums at the rear and no ABS on yours??
Compared with your other Citroen's, and some other conventional cars, the ZX brakes can have a longish travel. Experience with lots of them is what tells you if it is just the norm or one that needs attention. Yours does sound a little excessive though. So...
110% sure all the air is out? Do you use a pressure bleeder?
This is so commonly rear shoes, I've said before here the rear shoes do not need to be worn thin to do this. It's odd but the difference in lining thickness between good and no good is very small. To be honest if I find this problem on a car with a mileage between 60K & 120K the rear shoes are often the originals...they look "OK" but replacing them does the trick nine times out of ten.
Also look at the drums. Many folks will curse a wear lip making them hard to get off and grind it away. If the lip is that bad then the drums are worn enough to lose quite a lot of the adjuster range.
Are you setting the auto adjuster up manually to get the shoes as close as possible to the drums when you're putting them back on. I've had adjusters that look OK but actually don't take up themselves at all.
What about the front discs? Excess runout here will push the pads back further than normal in the brake off condition and increase pedal travel a little.
Lastly the master cylinder. On possibly one in ten with this fault these days I've needed to replace the master cylinder. Like the shoes the master cylinder seals don't always look terrible but it sorts the problem.
In your situation I'd order a new set of shoes from GSF before thinking of anything else.
Oh and a little trick. If you get someone else to push the pedal very slowly while you have an ear to the rear drums you can often just hear the shoe movement while that "free play" is being taken up on the pedal. Usually you hear the return springs as they stretch. This will rather confirm where all the lost movement is.
David
Have we talked of this before? Drums at the rear and no ABS on yours??
Compared with your other Citroen's, and some other conventional cars, the ZX brakes can have a longish travel. Experience with lots of them is what tells you if it is just the norm or one that needs attention. Yours does sound a little excessive though. So...
110% sure all the air is out? Do you use a pressure bleeder?
This is so commonly rear shoes, I've said before here the rear shoes do not need to be worn thin to do this. It's odd but the difference in lining thickness between good and no good is very small. To be honest if I find this problem on a car with a mileage between 60K & 120K the rear shoes are often the originals...they look "OK" but replacing them does the trick nine times out of ten.
Also look at the drums. Many folks will curse a wear lip making them hard to get off and grind it away. If the lip is that bad then the drums are worn enough to lose quite a lot of the adjuster range.
Are you setting the auto adjuster up manually to get the shoes as close as possible to the drums when you're putting them back on. I've had adjusters that look OK but actually don't take up themselves at all.
What about the front discs? Excess runout here will push the pads back further than normal in the brake off condition and increase pedal travel a little.
Lastly the master cylinder. On possibly one in ten with this fault these days I've needed to replace the master cylinder. Like the shoes the master cylinder seals don't always look terrible but it sorts the problem.
In your situation I'd order a new set of shoes from GSF before thinking of anything else.
Oh and a little trick. If you get someone else to push the pedal very slowly while you have an ear to the rear drums you can often just hear the shoe movement while that "free play" is being taken up on the pedal. Usually you hear the return springs as they stretch. This will rather confirm where all the lost movement is.
David
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uhn113x
- Posts: 1161
- Joined: 06 Jan 2004, 22:06
- Location: Near Leeds, United Kingdom
- My Cars: 1981 Dyane - on road all year round.
1982 GSA Pallas - on road April - September.
1997 ZX 1.9D Dimension. - x 1
Hi David
Thanks for your response - I was hoping you would come on this one. I did raise it before; that was before I had a look at the rears. It looks as if the shoes have been replaced fairly recently, and as noted, there is quite a bit of thread left on the adjusters - that after backing them right off and pumping the pedal to activate them.
Yes, no ABS
There is hardly any wear lip on the drums
I only bled them in the conventional way, and feel fairly confident that all air is out because the pedal feels fairly solid with the engine not running.
I will try presetting the adjusters, although I can only just get the drum off when they have set themselves.
I am fairly certain that all the play occurs before the master cylinder plunger is contacted by the pushrod, hence me wondering if adjustment here was advisable, otherwise it may be the 1 in 10 that need a master cylinder; if it comes to this I will measure the projection of the rod when I remove it - doesn't look like too bad a job, but presume intercooler will have to come off as per BOL?
Thanks for your response - I was hoping you would come on this one. I did raise it before; that was before I had a look at the rears. It looks as if the shoes have been replaced fairly recently, and as noted, there is quite a bit of thread left on the adjusters - that after backing them right off and pumping the pedal to activate them.
Yes, no ABS
There is hardly any wear lip on the drums
I only bled them in the conventional way, and feel fairly confident that all air is out because the pedal feels fairly solid with the engine not running.
I will try presetting the adjusters, although I can only just get the drum off when they have set themselves.
I am fairly certain that all the play occurs before the master cylinder plunger is contacted by the pushrod, hence me wondering if adjustment here was advisable, otherwise it may be the 1 in 10 that need a master cylinder; if it comes to this I will measure the projection of the rod when I remove it - doesn't look like too bad a job, but presume intercooler will have to come off as per BOL?
Hi Mike, I had a prob with my ZX brakes when I swopped them for Volcane brakes. My brakes too had a very long travel at times but worked fine.
On my car the travel varied from one application to the next though they always worked, it was cured by fitting a new master cylinder.. My brakes are very very good now. [:)]
*Aside* Shame you couldn't make the meeting, I was looking foreword to a ride in your DS [8)] [:D] [:o)] [^]
On my car the travel varied from one application to the next though they always worked, it was cured by fitting a new master cylinder.. My brakes are very very good now. [:)]
*Aside* Shame you couldn't make the meeting, I was looking foreword to a ride in your DS [8)] [:D] [:o)] [^]
You should be able to eliminate back brake adjustment by applyig a little pressure on the handbrake and seeing if there is any difference on the SECOND application. Be very careful as these cars have a diagonally split system and if the rear brakes get very hot they can boil the fluid - leading to a (generally) temporary failure of a circuit. As with the handbrake you are heating both that means total failure! (had one do this on a Renault 21 with a very similar system)
I had handbrake problems with the Renault and dismantled and cleaned it etc and assembled dry as haynes didn't say anything about lubrication and I wasn't sure if it would cause more problems by attracting dirt. It was still not adjusting properly so next time I carefully greased the screw and nut of the adjuster and it worked properly.
Jeremy
I had handbrake problems with the Renault and dismantled and cleaned it etc and assembled dry as haynes didn't say anything about lubrication and I wasn't sure if it would cause more problems by attracting dirt. It was still not adjusting properly so next time I carefully greased the screw and nut of the adjuster and it worked properly.
Jeremy
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uhn113x
- Posts: 1161
- Joined: 06 Jan 2004, 22:06
- Location: Near Leeds, United Kingdom
- My Cars: 1981 Dyane - on road all year round.
1982 GSA Pallas - on road April - September.
1997 ZX 1.9D Dimension. - x 1
James
You would have been welcome to a ride in the DS!
I am convinced that the free travel is before the pushrod contacts the master cylinder - there is virtually no resistance except the pedal spring. Never had a ZX m/cyl to bits, but others I have done usually have a circlip to limit the rearward travel of the piston, so maybe the problem can be cured by adjusting the pushrod - I wonder if the pedal or pedal box is distorted or something?
Jeremy
I think rear brakes are OK; if you put the handbrake on 2 clicks, they drag severely, so, to me, that means the rear shoes have the minimum clearance. If you slacken the adjusters off, put the drums back, pump pedal to adjust, you can just get the drums back off.
I think I am going to adjust the pushrod and see what happens...
You would have been welcome to a ride in the DS!
I am convinced that the free travel is before the pushrod contacts the master cylinder - there is virtually no resistance except the pedal spring. Never had a ZX m/cyl to bits, but others I have done usually have a circlip to limit the rearward travel of the piston, so maybe the problem can be cured by adjusting the pushrod - I wonder if the pedal or pedal box is distorted or something?
Jeremy
I think rear brakes are OK; if you put the handbrake on 2 clicks, they drag severely, so, to me, that means the rear shoes have the minimum clearance. If you slacken the adjusters off, put the drums back, pump pedal to adjust, you can just get the drums back off.
I think I am going to adjust the pushrod and see what happens...
yes sounds as though the back brakes are ok. I seem to remember in the mists of time finding a master cylinder on some vehicle with a worn pushrod! - end hadn't been hardened properly or something.
I have had this problem of a cylinder not re-filling properly - on a Marina clutch - and the return spring had failed. I could get a proper action if i bled it with compressed airon the reservoir but as soon as that was removed it sank again. Master cylinders don't seem to be hideously expensive.
If you adjust the pushrod you must be very careful to ensure the piston returns properly to allow the seals to clear the recuperation holes which allow floud into the cylinder. your problems could be due to the pistons not returning propery - which would give an apparently slack pushrod.
jeremy
I have had this problem of a cylinder not re-filling properly - on a Marina clutch - and the return spring had failed. I could get a proper action if i bled it with compressed airon the reservoir but as soon as that was removed it sank again. Master cylinders don't seem to be hideously expensive.
If you adjust the pushrod you must be very careful to ensure the piston returns properly to allow the seals to clear the recuperation holes which allow floud into the cylinder. your problems could be due to the pistons not returning propery - which would give an apparently slack pushrod.
jeremy
-
uhn113x
- Posts: 1161
- Joined: 06 Jan 2004, 22:06
- Location: Near Leeds, United Kingdom
- My Cars: 1981 Dyane - on road all year round.
1982 GSA Pallas - on road April - September.
1997 ZX 1.9D Dimension. - x 1
Jeremy opined:<blockquote id="quote"><font size="1" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote">If you adjust the pushrod you must be very careful to ensure the piston returns properly to allow the seals to clear the recuperation holes which allow floud into the cylinder. your problems could be due to the pistons not returning propery - which would give an apparently slack pushrod.<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">
Yep - I am OK with that - I would only adjust by a fairly small amount, anyhow.
I think I will have a look and see if the clevis can be removed from the pedal to adjust it - hate working on pedal gear [:(] OK if you are 4ft 6 and have arms like Mr Tickle.
Failing that, I think it will be master cylinder off, check piston is coming right back, and look at pushrod projection. Has anyone noticed anything strange about the two measurements given in Haynes? Surely they are transposed?
Yep - I am OK with that - I would only adjust by a fairly small amount, anyhow.
I think I will have a look and see if the clevis can be removed from the pedal to adjust it - hate working on pedal gear [:(] OK if you are 4ft 6 and have arms like Mr Tickle.
Failing that, I think it will be master cylinder off, check piston is coming right back, and look at pushrod projection. Has anyone noticed anything strange about the two measurements given in Haynes? Surely they are transposed?