bigandy
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| posted on 1/3/07 at 06:18 PM |
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Pesky brake bleeding....
Evening all,
I'm having a few minor issues getting the brakes on my car to the point where I am happy with the pedal feel. I filled the brand new system
(all parts either new, or remanufactured) with Motul RBF600 fluid a while back now, and bled them then and got rid of what I thought was all the air
(using an Easibleed kit hooked up to my compressor @ 15psi).
Today I have spent a good couple of hours going round the calipers rebleeding them, and I now seem to be getting clean clear fluid from all bleed
nipples. However, the pedal still feels a bit soft, almost spongy, which would suggest there is still a load of air in there somewhere.
I have two wilwood master cylinders, and Sierra calipers. There are NO leaks anywhere, and I have been round and nipped up all the connections today
to make sure there is no air getting in at a joint.
I have played around a bit, and it seems that the front circuit is reasonable, there is a bit of softness. The rear circuit seems to be very soft
though.
Has anyone got any ideas as to how I can sort this out?
Cheers
Andy
Dammit! Too many decisions....
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RazMan
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| posted on 1/3/07 at 06:29 PM |
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Have you got the rear calipers mounted upside down? If so then you need to remove them (to get the nipples upward )to bleed them.
Cheers,
Raz
When thinking outside the box doesn't work any more, it's time to build a new box
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scottc
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| posted on 1/3/07 at 06:39 PM |
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clamp the hose at the rear caliper and see if the pedal is firmer.
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bigandy
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| posted on 1/3/07 at 06:41 PM |
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The Sierra rear calipers are mounted so that the bleed nipple is pointing roughly upwards (if you look at a side/plan view of the car, the caliper is
mounted to the rear of the axle line).
Like this: http://mysite.wanadoo-members.co.uk/lordandymk2/rearflexibrakelinesmall.jpg
Is it worth unbolting the caliper again, holding it up high so the bleed nipple is at the very top, then rebleeding?
Oh, and is it okay to clamp the goodridge flexi hoses with stainless braiding on? Don't want to damage anything... 
Cheers
Andy
[Edited on 1/3/07 by bigandy]
Dammit! Too many decisions....
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Wadders
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| posted on 1/3/07 at 06:43 PM |
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I have to unbolt all four calipers to bleed them properly, even using an eezybleed. wedge open the pads and as you start bleeding, play about with the
caliper turning it upside down, and on its side etc. Its amazing how much air comes out.
Al.
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rusty nuts
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| posted on 1/3/07 at 06:52 PM |
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Adjust the piston to pad clearance
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zetec7
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| posted on 1/3/07 at 07:06 PM |
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DON'T clamp the flexy lines, EVER!!! They can crack internally and may fail catastrophically when you need them most!!
Did you "bench-bleed" the master cylinders before installing them? I've always had success that way (and seldom had success if I
didn't). If not, there may be little pockets of air in the master cylinders that no amount of bleeding at the wheel ends is going to get out.
Personally, I'd take off the master cylinder(s) and bleed them on the bench to be sure, then re-install. Otherwise, you're never going to
know for sure, are you?
http://www.freewebs.com/zetec7/
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jollygreengiant
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| posted on 1/3/07 at 08:17 PM |
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Don't forget that, even if the pads and discs are new, it can still take up to 100miles of driving to get the pads to 'bed in' and
get the pedal to feel "right".
Beware of the Goldfish in the tulip mines. The ONLY defence against them is smoking peanut butter sandwiches.
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RazMan
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| posted on 1/3/07 at 08:26 PM |
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quote:
Originally posted by bigandy
Is it worth unbolting the caliper again, holding it up high so the bleed nipple is at the very top, then rebleeding?
It shouldn't be neccessary as you have them mounted the right way up - its just that most people have them mounted the other way up for various
reasons. I needed mine that way for the handbrake cables routing.
Oh and as already mentioned - not a good idea to clamp a flexy pipe, certainly not a braided one.
Cheers,
Raz
When thinking outside the box doesn't work any more, it's time to build a new box
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daviep
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| posted on 1/3/07 at 08:33 PM |
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Are all your calipers sliding freely? Stuck caliper can make the pedal feel spongy.
Just a thought.
Davie
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britishtrident
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| posted on 1/3/07 at 08:41 PM |
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If you have proper flexy hoses not metal braided ones it is perfectly safe to clamp them, the old style official Girling special tool is the best.
The advice you have been given about bleeding is good but remember even with a pressure bleeder the pedal must be depressed fully at some point during
bleeding also the pedal should be held to the floor while each nipple is closed.
Usual remarks about the rear self-adjusters and handbrake cable tension adjustment apply.
The Jollygreen has a good point about the pads bedding but it could also be that the caliper brackets are not perfectly true to the disc --- this can
give a lot of lost motion and a very spongey feel to the pedal.
The other possible cause is lack of stiffness in the pedal box or its mounting --- the stiffness required is often underestimated by a lot of kit
and racing car builders.
[Edited on 1/3/07 by britishtrident]
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BenB
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| posted on 1/3/07 at 08:53 PM |
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Bleed, bleed, and bleed again....
And give the calipers a few good clunks with a soft faced hammer during the Easibleed bleeding... always works for me....
Holding the brake pedal down overnight (I believe a brick is traditional) also helps.. as does a few miles of shake down (which as well as shaking up
the bubbles also beds in the brakes)......
[Edited on 1/3/07 by BenB]
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RazMan
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| posted on 1/3/07 at 08:55 PM |
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quote:
Originally posted by BenB
.. as does a few miles of shake down (which as well as shaking up the bubbles also beds in the brakes)......
A very good point - there is no substitute for some road testing, but make sure you can at least stop!
Cheers,
Raz
When thinking outside the box doesn't work any more, it's time to build a new box
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bigandy
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| posted on 1/3/07 at 09:29 PM |
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Thanks for the responses/tips chaps, they are much appreciated.
I did try to fill the master cylinders before installing them, although it was just a casue of using a syringe to put some fluid into them
carefully.
I think I shall spend a while tomorrow unbolting all the calipers/master cylinders and give them a few taps with a hide mallet to try and dislodge any
bubbles. I shall then have another bleeding bleeding session and see how I go.
I'm a fair way from a shakedown drive yet though, still not got an engine in!
Cheers
Andy
Dammit! Too many decisions....
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Danozeman
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| posted on 1/3/07 at 09:31 PM |
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As britishtrident has said. Make sure the rear brakes are adjusted properly and pump the pedal a couple of times while the easy bleed is on there.
Or forget the easy bleed and get someone to push the pedal up and down while u crack the nipples off.
If u can give it a drive aswell. It will help wonders.
Dan
Built the purple peril!! Let the modifications begin!!
http://www.eastangliankitcars.co.uk
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RazMan
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| posted on 1/3/07 at 10:05 PM |
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quote:
Originally posted by bigandy
I'm a fair way from a shakedown drive yet though, still not got an engine in!
Ah.. yes.. well 
Cheers,
Raz
When thinking outside the box doesn't work any more, it's time to build a new box
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bigandy
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| posted on 1/3/07 at 11:02 PM |
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Just had a thought, I could get SWMBO and the pensioners from across the road to push the car up and down the street whilst I man the steering/brakes
Cheers
Andy
PS. although this bleeding is a bit of a pain, I'm still surprised that I only had one weeping joint around the brake pressure switch!
Dammit! Too many decisions....
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RazMan
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| posted on 1/3/07 at 11:11 PM |
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You'll be lucky - If I ask swmbo if I can 'borrow her foot again' she just tuts at me
Cheers,
Raz
When thinking outside the box doesn't work any more, it's time to build a new box
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02GF74
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| posted on 2/3/07 at 10:47 AM |
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do you have rubber hoses or braided ones?
with the rubber ones, thinjk they were new, I had absoluteluy awful braking - had to sit back a long way from the car in front (but SVA brake
test siad they were fine).
Now either there was air in the lines - I bleed them loads or the rubber hose was not as good as I though and they were expanding.
Anyways, since fitting the braided hoses, goodridge, brakes are an awful lot better.
So story is .... what hoses do you have fitted, if braided then dunno, has to be air in the lines somewhere I guess.
you've checked pistons are moving?
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bigandy
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| posted on 2/3/07 at 02:57 PM |
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I've got goodridge braided flexis on all four corners, the only rubber pipes are between the fluid reservoir and the master cylinders.... The
pistons are all moving okay (wheels can be rotated by hand with the brake pedal not pressed, and not when the brake pedal is gently pressed....
Just about to venture out into the garage to have another attempt at getting the air out of the system. There must be a fair amount still in
there!
Cheers
ANdy
Dammit! Too many decisions....
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britishtrident
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| posted on 2/3/07 at 03:18 PM |
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quote:
Originally posted by 02GF74
do you have rubber hoses or braided ones?
with the rubber ones, thinjk they were new, I had absoluteluy awful braking - had to sit back a long way from the car in front (but SVA brake
test siad they were fine).
Now either there was air in the lines - I bleed them loads or the rubber hose was not as good as I though and they were expanding.
Anyways, since fitting the braided hoses, goodridge, brakes are an awful lot better.
So story is .... what hoses do you have fitted, if braided then dunno, has to be air in the lines somewhere I guess.
you've checked pistons are moving?
The difference in pedal movement between the two types of hose is more immaginary than real.
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DarrenW
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| posted on 2/3/07 at 03:27 PM |
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quote:
Originally posted by britishtrident
quote:
Originally posted by 02GF74
do you have rubber hoses or braided ones?
with the rubber ones, thinjk they were new, I had absoluteluy awful braking - had to sit back a long way from the car in front (but SVA brake
test siad they were fine).
Now either there was air in the lines - I bleed them loads or the rubber hose was not as good as I though and they were expanding.
Anyways, since fitting the braided hoses, goodridge, brakes are an awful lot better.
So story is .... what hoses do you have fitted, if braided then dunno, has to be air in the lines somewhere I guess.
you've checked pistons are moving?
The difference in pedal movement between the two types of hose is more immaginary than real.
Im sure many people will argue against the last statement to justify the expense of the braided but i have to agree to a point. Braided may be good
for race applications etc but on normal road cars the true value may not be cost effective if you have new std hoses fitted initially. Braided do look
good though.
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martyn_16v
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| posted on 2/3/07 at 07:07 PM |
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quote:
Originally posted by DarrenW
Im sure many people will argue against the last statement to justify the expense of the braided but i have to agree to a point. Braided may be good
for race applications etc but on normal road cars the true value may not be cost effective if you have new std hoses fitted initially. Braided do look
good though.
It's probably a bit like the whole 'performance' spark plugs thing, there's no way a spark plug can increase power, but tired
old ones can lose power, so people convince themselves that the extra dosh they've spent was worth it even though the 'gain' they
just got would have been the same if they'd just fitted a new set of properly gapped standard plugs instead.
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