BenB
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| posted on 26/2/09 at 12:55 PM |
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Borrocks- tin top brake problems part 99012
Can serious amounts of air in a brake circuit lead to a creeping pedal?
I'm trying to replace the brake pads on the tintop Megane.
I've replaced the brake pads eventually (got the proper brake wind back tool) but now I've got a new problem. As instructed in the book of
lies I opened the bleed nipple a bit and put a hydraulic hose clamp around the flexi hose before doing the wind-back. However, now I've got a
problem whereby the brake pedal is very long and pretty ineffective and although it goes stiff with a few rapid pumps it sinks back down to the floor
over 20-30 seconds.
I can't imagine the MC seals would be that knackered that it would cause the long pedal and the ineffectual brakes so they definately need
bleeding but beyond that?? There's no obvious leak from the MC but a rather disturbing hissing noise from the direction of the MC when I press
the pedal....
Could this all be due to air in the system? Or have I managed to flip the MC seal despite my best efforts not to????
I think I may have just managed to break both my tintop and my Locost 
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Mr Whippy
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| posted on 26/2/09 at 01:01 PM |
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As you pump the pedal the air inside heats up and expands, hence the pedal gets harder. As it rapidly cools the air contracts and the pedal sinks.
Classic sign of air in the system, more bleeding needed unfortunately. The noise is the air rushing through the small holes in the cylinder, perhaps
the fluid level fell too low when the pads were worn and air was sucked in, often happens when you brake over a bump
[Edited on 26/2/09 by Mr Whippy]
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BenB
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| posted on 26/2/09 at 01:02 PM |
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That's what I'm hoping  Air in the system I can deal with. A shagged MC seal I'm not so confident on!! For one it's a pig of
a job cos it's hidden under lots of engine bits.....
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r1_pete
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| posted on 26/2/09 at 01:04 PM |
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Are you sure you haven't run the master cylinder dry? I usally wind the pistons back in and watch the fluid in the reservoir rise to above max
before letting it out of the bleed screws.
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BenB
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| posted on 26/2/09 at 01:08 PM |
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I'm just wondering the same. I stupidly got on the car after putting on the new pads and started the engine. Not suprisingly the pedal sank
pretty low. Wonder if I got air into the MC at that point.....
Anyone know if the screw-caps that come with Eezi-bleeds work with Renault MCs???
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02GF74
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| posted on 26/2/09 at 01:23 PM |
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there are a variety of caps that can be purchased for easzi-bleed. the standard one is universal. it is suposed to fit Land Rover master, guess who
had to mpop up brake fliuid! 
2 man bleeding I have found to be best.
you can make one man bleed tool from a piece of tubing, plug in a flared brake pipe, blocked at one end and with 1 mm hole in its side. get another
piece of tubing to cover over the hole = one way valve. then off you go.
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theconrodkid
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| posted on 26/2/09 at 01:35 PM |
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sounds like you sha**ed the master cyl,the hissing noise is the servo.
when pumping up after pads etc its best to give short pumps rather than all the way to the floor.
remember if the discs are a bit manky it can take some time for the pads to bed in and the pedal to improve
who cares who wins
pass the pork pies
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BenB
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| posted on 26/2/09 at 01:45 PM |
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I think I've shagged the servo. Not sure how though!!
The hissing noise only happens when the engine is running. If I leave the car for a while the brake pedal is firm, if I press the pedal and start the
engine it sinks to the floor.
My thinks my servo is kaput. How the hell that happened though I don't know......
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Mr Whippy
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| posted on 26/2/09 at 01:55 PM |
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quote:
Originally posted by BenB
I think I've shagged the servo. Not sure how though!!
The hissing noise only happens when the engine is running. If I leave the car for a while the brake pedal is firm, if I press the pedal and start the
engine it sinks to the floor.
My thinks my servo is kaput. How the hell that happened though I don't know......
your servo should hold its vacuum for at least a day or more, if you turn the engine on, then off leave it a few hours then lever aside the hose
connector it should still hiss as air rushes in, if not the diaphragm inside has got a puncture. Not usually serviceable
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02GF74
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| posted on 26/2/09 at 02:00 PM |
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quote:
Originally posted by BenB
I think I've shagged the servo. Not sure how though!!
The hissing noise only happens when the engine is running. If I leave the car for a while the brake pedal is firm, if I press the pedal and start the
engine it sinks to the floor.
My thinks my servo is kaput. How the hell that happened though I don't know......
hmmm. all the servo should do is assist you in pressing the pedal i.e. making it easier to press.
the brake pedal should not travel any further but will be harder to press.
I don't buy the servo bit - there is no way a servo can supply enough force to push a brake pedal down on a properly set up brake system.
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BenB
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| posted on 26/2/09 at 02:10 PM |
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This is getting very bizarre. Reading up on the net it appears that the pedal sinking a bit when the engine is started is normal for a system with a
servo.... Perhaps it is just air zooming around in the master cylinder (still got my fingers (and everything else) crossed.... Can't think why
that wouldn't occur with the engine switched off though....
Oh well, logic has lost, time for a process of elimination 
Hope it's not the servo. Doesn't look a huge job but £100 for the part is a bit painful....
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Mr Whippy
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| posted on 26/2/09 at 03:23 PM |
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procedure below to check the servo and brakes
Servo -
pump the brakes about 5 times, put your foot on the pedal and press down, start the engine pedal sinks a bit and goes lighter (servo now working)
Switch off engine and pump the pedal about 5 times, it should go hard again (servo now drained of a vacuum, not functioning)
If its hard all the time then servo is doing nothing and is probably faulty
Brakes -
If you pump the pedal about 5 times till it goes hard, wait 10 seconds, pump it again rapidly and it gets even harder then thats air in the system
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Cousin Cleotis
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| posted on 26/2/09 at 04:48 PM |
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Is it creeping with or without the engine running?
Alot modern cars will have pedal creep, do you press the brake pedal that hard when you are driving?
Paul
[Edited on 26/2/09 by Cousin Cleotis]
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ashg
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| posted on 26/2/09 at 05:34 PM |
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has it got abs?
little tip if it has! bleed the brakes with the igniton on ;-)
as for one man bleeding halfords do a bleeding pipe which has a one way valve in it allowing you to crack the bleed nipple go pump the brake and then
get out and do the bleed nipple up. they are £5 well worth the money.
Anything With Tits or Wheels Will cost you MONEY!!
Haynes Roadster (Finished)
Exocet (Finished & Sold)
New Project (Started)
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BenB
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| posted on 26/2/09 at 05:59 PM |
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Do you mean with the engine running or just the ignition on? I really should look up how ABS works- didn't know how servos work until
earleir!!!
Wierd thing is the test described by MW for the Servo suggests it's okay!!!
Very strange!!! Especially as the hissing appears to be coming from the glove compartment which is where the back of the servo is..... I suppose it
could just about be air passing through the MC making noise which is being transmitted through the MC-servo connecting rod to the Servo which is
acting as a sound chamber and amplifying it... ?? wishful thinking. we'll see.....
I'm hoping it's just air in the system. I'm like the people who write for Practical Classics / PPC etc IE three cars now, none of
which are actually working
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Werner Van Loock
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| posted on 26/2/09 at 06:46 PM |
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We have a Espace IV and it does the exact same thing.
Engine off, hard pedal
Engine on, goes all the way to the floor then with the hissing sound
http://www.clubstylus.be
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Cousin Cleotis
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| posted on 26/2/09 at 07:16 PM |
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the hissing sound is air entering the pedal side of the servo, thats how they work, they use atmospheric pressure to provide the assistance. As long
as you have a hard pedal without the engine running, and it stops as it should when you are driving it is fine.
Drive along at 30 mph and press the brake pedal as hard as you do to make it creep when you are at a standstill, make sure no one is behind you, that
should give you confidance the brakes are fine.
Paul
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tomblyth
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| posted on 26/2/09 at 07:51 PM |
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Had this on a cleo sport! fill it with new fluid use an easybled bottle and open the rear N/s then front O/s followed by the rear O/s then front N/s
. checking the level in the easy blead often . you cant bleed this system without an easibled. (only put 10 psi in the tire supplying the
easibleb...)
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BenB
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| posted on 26/2/09 at 07:56 PM |
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Blimey. Sounds like it might not be as screwed as I thought it was.
Just "tested" the brakes on an empty bit of road. I think I've given myself whiplash!! Sure stops quickly once you get past the
initial sponginess.
I'm coming round to the idea that maybe it's just air in the system leading to a spongy pedal and the reason I haven't heard the air
entering the servo before is because I haven't sat in the car like a gimp pumping the pedal with the engine running before!!
Don't panic! Don't panic!
I'll bleed the system on Saturday and see how that goes. Always thought it was rather over-servo'd anyway (though I suspect that was
actually the fact that there wasn't any friction material left on the brake pads and the snatching was due to the backing plate welding itself
onto the disc!!!)....
Cheers for the moral support and advice. Perhaps it's a case of "they all do that, Sir"....
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BenB
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| posted on 1/3/09 at 09:43 PM |
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LOL! Bled the system and brakes back to over-servod norm.... Looks like the squishy noise is normal and I've just ignored it before!! LOL!!!
What a dufus....
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