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        General >> Problems >> Rear Brakes 'Bleed or Not to Bleed'
        
(Message started by: gerryw on Jun 29^th, 2007, 5:01pm)

Title: Rear Brakes 'Bleed or Not to Bleed'
Post by gerryw on Jun 29^th, 2007, 5:01pm

Hi all,

I have just replaced the rear pads on my '97' Cossie and the brake pedal is very spongy (it travels a long way).

I carried out the renewal to the letter following the instructions of this website and it did not mention anything about bleeding the rear brakes. I did not open any brake pipes etc to the air so why is the brake pedal so spongy?

Any help would be gratefully accepted!

Regards
Gerryw

Title: Re: Rear Brakes 'Bleed or Not to Bleed'
Post by scorpio_man on Jun 29^th, 2007, 5:09pm

hi there

you may have got air in when screwing back the pistons. :-/ what's the level like now?

Title: Re: Rear Brakes 'Bleed or Not to Bleed'
Post by jonnycab on Jun 29^th, 2007, 5:37pm

May just be the pads wearing in :)

Title: Re: Rear Brakes 'Bleed or Not to Bleed'
Post by mr._floppy on Jun 29^th, 2007, 5:50pm

Did you ensure the little pimple on the back of the pads lined up with the recess on the piston face ?

Tut tut ;)

A real b****r I know, but it might be advantageous to re-check as your new pads and the disc will wear unevenly .

Title: Re: Rear Brakes 'Bleed or Not to Bleed'
Post by gerryw on Jun 29^th, 2007, 6:08pm

Hi all,

1st Scorpio_man: The brake fluid level is spot on but I did have to undu the piston fully out to get them to screw all the way back in. Could this let air in?

2nd jonnycab: There seems to be to much travel in the brake pedal to be just the new pads wearing in. The brake pedal near travels to the floor on braking?

3rd mr_floppy: The instructions I followed from this site did not mention anything about pimples on the rear of the pads lining up with the piston recesses. I did not even notice them. Will the pimples be on the back of the old brake pads?

Many thanks to you all for replying to my question. if any of you have any more inputs on my gbrake situation I would be grateful.

Regards
Gerryw

Title: Re: Rear Brakes 'Bleed or Not to Bleed'
Post by Highlander on Jun 29^th, 2007, 11:16pm

yep, unscrewing the pistons can let air, need to bleed them

Title: Re: Rear Brakes 'Bleed or Not to Bleed'
Post by mr._floppy on Jun 30^th, 2007, 2:19pm

Yep, check the old pads , the pimples stop the piston turning when the handbrake is operated.

Don't touch that bleed screw !

Difference of opinion here, as Jimmy Tarbuck used to say on that Tv game show which I've forgotten the name of, I can't see how turning the piston lets in air. ???

Title: Re: Rear Brakes 'Bleed or Not to Bleed'
Post by Highlander on Jun 30^th, 2007, 4:03pm

on 06/29/07 at 18:08:41, gerryw wrote:

I did have to undu the piston fully out to get them to screw all the way back in. Could this let air in?

He unscrewed them all the way out, air would have got in behind them at this point (and obviously has)

Even if the pads were not inserted correctly the brakes would not feel spongy and have excess travel, it must be air in the system

Title: Re: Rear Brakes 'Bleed or Not to Bleed'
Post by Spannerdemon on Jul 1^st, 2007, 10:08am

Can't see what you're worried about. Bleeding the brakes is such an easy job. Get a one man bleeding tube "Eazibleed" are excellent, for about £2.99, and a bottle of brake fluid, and an old jam jar, and you'll have it done in half an hour.

You'll probably be amazed at how much air is in the pipes, and there WILL be air in them because you've removed the piston.

One things for sure, you don't want to be driving around with anything but 100% perfect brakes. The difference between having them spongy, and working 100% is huge, and you don't want to find it out the hard way by ploughing into the back of somebody's car. ;)

Title: Re: Rear Brakes 'Bleed or Not to Bleed'
Post by mr._floppy on Jul 1^st, 2007, 11:15am

I agree with Spanner, , the Scorp has been the easiest Bleeder I've known.

But beware opening, or attempting to open, the bleed screws can be fraught with danger . Usually they've not been touched for years and the previous owner has tightened them with a lorry torque bar ( Please, everyone, finger tight then an eighth of a turn, that's all they need ).

So plenty penetrating fluid , and a 6 point ring spanner or socket will do it , open ended spanners are a no no. :-*

Title: Re: Rear Brakes 'Bleed or Not to Bleed'
Post by Spannerdemon on Jul 1^st, 2007, 9:11pm

Quote:

Please, everyone, finger tight then an eighth of a turn, that's all they need ).

[]. Plenty of WD40 on the bleed screws 24 hours before you do them, and you shouldn't have any problem. Undo them GENTLY a bit at a time. Any resistance, take them clockwise again, and then anti clockwise until they give up and see it your way!! ;D

Why in God's name people feel that they have to do the Godzilla bit on delicate bleed screws escapes me. ;)

Title: Re: Rear Brakes 'Bleed or Not to Bleed'
Post by Highlander on Jul 1^st, 2007, 10:05pm

on 06/30/07 at 14:19:25, mr._floppy wrote:

Don't touch that bleed screw !

Difference of opinion here, as Jimmy Tarbuck used to say on that Tv game show which I've forgotten the name of, I can't see how turning the piston lets in air. ???

Winner takes all, what did I win?? ;D

Title: Re: Rear Brakes 'Bleed or Not to Bleed'
Post by gerryw on Jul 2^nd, 2007, 1:31am

Hi again,

First of all mr_floppy, you were right about the pads and the pimples. I stripped and rebuilt the brakes resetting the brake pads and also stationed the pistons in the correct position to let the 'pimple' situate itself in the slot where the brake tool fits. Its not easy to make sure the pads are located correctly, I had to squeeze under the wheel hub with a torch to make sure that the pads were indeed flat against the Disks!

The brakes pedal is still spongy although not as bad as before so I am thinking that air must of got in somehow so Monday Im going to bleed the rear brakes with a little help from a friend & WD 40...

I will let you know how it goes.

Thanks to all who replied to my query and hopefully tomorrow will see the completion of what was initially a 1 hour job (silly me for thinking that it would be so easy)

Regards
Gerryw

Title: Re: Rear Brakes 'Bleed or Not to Bleed'
Post by sector-9 on Jul 2^nd, 2007, 5:17pm

Be careful with the bleed nipples - the back one rounded off on mine trying to undo it, whereas the front one sheared in half! I'm going to try getting a 2nd hand front caliper, but replace both back ones with recons as the handbrake mechanism has seized on one of them already (the one with the rounded nipple) but the other probably isn't much better. Good news is around £45. ex. VAT each for rear calipers from local auto spares shop.

Darren

Title: Re: Rear Brakes 'Bleed or Not to Bleed'
Post by gerryw on Jul 3^rd, 2007, 3:48pm

Hi all,

Well Ive done it,

Took off both rear wheels and applied liberal amounts of WD 40, left it for approx 30 mins then went back and started the 'Bleedin' thing (ha ha).

But seriously, I found the bleed screws quite easy to undo, I used a ring spanner and held it at the bleed screw end with my left hand and just used the heel of my right hand to gently prod the spanner from about 50mm and the bleed screws gently eased off.

Had my girlfriend do the honors on pressing the brake pedal (well its allowed, isnt it)? while I opened and closed the bleed screw to get rid of the air.

There is one thing that I did which I overlooked previously, If you install new brake pads as normal and bleed them you will get a wrong brake pressure signal if you dont start your engine to bring the brake pressure up. I didnt the 1st time and I thought 'Great' the brake pressure was nice and firm, job done, but when I went to take my car for a run to test the brakes the brake pedal went to the floor (bottle went) so lesson learnt!

Anyway back to the job, bled all the air from the rear brakes with the engine running and on completion the brake pedal was just right (within tolerances regards to the new pads bedding in (about 50/100 miles?).

So, thanks again for all your input and I have really learnt alot from all your replies, cheers.

Regards
Gerryw

p.s I have some corrosion to the underbody, have any of you any remedies regarding this?

Title: Re: Rear Brakes 'Bleed or Not to Bleed'
Post by mr._floppy on Jul 4^th, 2007, 12:34am

Congrats , a job well done, and saved yourself a small fortune by not taking it to your local garage and learned something in the process :-*#

As to the rust, if its just surface , try some rust inhibitor, if it's structural and rotting then it's a job for the welder I'm afraid.

Title: Re: Rear Brakes 'Bleed or Not to Bleed'
Post by pat on Jul 4^th, 2007, 1:21am

My wife swears by aloe vera and it cleared hers }{ }{

Title: Re: Rear Brakes 'Bleed or Not to Bleed'
Post by pat on Jul 4^th, 2007, 1:46am

Hi Gerry.
Sorry-didn't mean to be facetious. Depends how advanced the corrosion is. If it has gone through or the area is weak, then it needs welding. If it is just surface rust, then painting it with old engine oil or Waxoyl should keep it at bay.

Title: Re: Rear Brakes 'Bleed or Not to Bleed'
Post by Spannerdemon on Jul 4^th, 2007, 8:16am

Well done for tackling the job yourself.

If more people did this, they would realise what absolute rip-off prices garages charge to do basic maintenance. ;)

Title: Re: Rear Brakes 'Bleed or Not to Bleed'
Post by sector-9 on Jul 7^th, 2007, 8:40pm

Well today I replaced my rear discs, pads and calipers and I have similar problems to the OP - pressing the pedal with the engine off it is nice and firm, but with it switched on it is quite soft, and worryingly, will slowly sink to the floor. Now I don't think it's a problem with the master cylinder as it all worked fine this morning until I replaced the calipers, so it's probably trapped air somewhere. Thing is, I used one of those pressure bleeding kits and at first loads of bubbles came out of each new caliper, but now it's just new brake fluid whenever I slacken the bleed nipples. Rear brakes do work fine however, though I had to cut the handbrake cable to remove the old caliper as the plastic end had stuck in the casting and it snapped off trying to remove it.

Is it possible air has got into the front circuits (shouldn't as they are separate) and causing this? I hope not because one of them has a snapped nipple so I can't bleed that one, though I am intending to replace it within the next week. I also ran out of brake fluid - used about 500ml bleeding the rear calipers - so I'll need to get some more of that too.

Finally, the new rear caliper on the passenger side seems to be binding - the wheel is very hot and you can smell the brake burning when near it. Because I only fitted these today, is it possible the caliper is faulty, or is there something I may have done wrong?

Basically, these brakes are p****** me off as I've already spent £140 on the rear and it looks like spending that again to do the front, and I've a holiday coming up in two weeks... >:(

Darren

Title: Re: Rear Brakes 'Bleed or Not to Bleed'
Post by petehull on Jul 7^th, 2007, 9:06pm

Is it possible that the hanbrake needs adjusting on the caliper? Are the pistons screwed right back into the cylinders, jack up and spin the wheels to determine any binding.

Pete

Title: Re: Rear Brakes 'Bleed or Not to Bleed'
Post by sector-9 on Jul 7^th, 2007, 10:34pm

Handbrake cable is disconnected from both calipers as I had to cut through it to remove one of the old ones! When I assembled the calipers and pads, neither wheel was binding. The rear right one isn't either (gets warm from normal braking, but no more than any other wheel), however the rear left one is definitely getting hot. I haven't jacked up the car again since because I've spent all afternoon on the brakes and made a mess of my dad's driveway (which he won't forget in a hurry). In any case, without fresh DOT 4 I can't continue bleeding the system, and I'm not sure that'll I bother until I can replace the front discs, pads and calipers later in the week. Pretty certain that with the new calipers on the front I'll be able to bleed the whole system and get rid of the spongy pedal. However, I'm wondering whether to take the 'new' rear right caliper back and get that swapped as I can't think of a reason why it would bind when the other side is free and all the components are new...

Darren

Title: Re: Rear Brakes 'Bleed or Not to Bleed'
Post by mr._floppy on Jul 7^th, 2007, 11:14pm

Are the " new " rear calipers new, reconditioned or from a reputable scrappy ( a debateable phrase, but that's a whole other discussion :-* ) ? if they're from a scrappy it could be a sticking piston or maybe rusty guide pins .

Ditch the pressure bleeding kit and try the " One man Kit " £6 from Halfords or the old tube and jam jar method, remember with new calipers there's a fair amount of empty space in the piston voids to fill with fluid before you can be sure all air has been removed.

Remember, and other posters may be appalled, as long as it's clean , you can save the expelled brake fluid and use it again if it requires extended bleeding . At a £5 for 250ml, why waste it ?

Title: Re: Rear Brakes 'Bleed or Not to Bleed'
Post by sector-9 on Jul 8^th, 2007, 11:18pm

The calipers are reconditioned from local auto factors (basically s/hand but have been painted silver and had overall kit fitted - but for the price of the kit and labour it's not worth doing myself).

I've now ordered another £170 worth of brake parts - complete everything for the front, plus the handbrake cable I had to cut through, and new engine oil and filter. Hoping I can fit it all next weekend. A lot of money spent, with no guarantee that it won't fail the MOT on something else, but at least the brakes should be 100% and not need touching again whilst I've got the car, especially as I'm planning on running it into the ground unless I give in to temptation and buy a Disco...

Think the binding back brake is sorted now: dismantled both rear brakes again but this time I scraped all the crud off the surfaces of the caliper carrier that the pads contact, and applied copper grease to the backs of the pads, the carrier and the caliper contact point. I've also greased the slide pins, though they weren't sticking. Finally I smeared some grease on the disc itself. All of the above seems to have done the trick and after a 75 mile trip it seems to be no warmer than the others.

Darren

P.S.

I've bought another 2ltrs of brake fluid as the new front calipers will need a fair bit to fill them, and I'll bleed the whole system front to back.