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LCR brake bleeding problem

Cupr-o-matic

Active Member
Jan 2, 2010
10
0
Hey guys,

I know this has been covered alot, but can anyone help?

Replaced both rear calipers the other day due to seizing handbrake, handbrake issue solved but now have long pedal travel and a hiss on depression (from servo I guess).

So, I bled the system using an eezibleed, followed the correct pattern for all bleed nipples inc clutch and master cylinder but cant seem to regain braking power or stop the pedal from sinking almost to the floor.

In my stupidity I accidentally floored the pedal whilst bleeding the system but I can't see that there is a vac leak (aka torn servo), as the idle vac is constant at about 20in Hg. Is there a possibility I could have flipped a seal in the MC? If so, what are the symptoms for this? I've taken it out for a test and can't get the ABS to engage but no dash management lights are showing.

Could it also be possible that the ABS unit has dragged in some air? I kept the res full at all times so no air could have got in to the system via the top but I understand that when replacing calipers air can make it's way back to the MC.

At this point braking power is very poor, put in new pads all round but that doesn't account for this.

Please help guys, thanks.
 

andycupra

status subject to change
if its safe to use the car, (carefully) id say use it. many a time people have suffered from this and in combination with new pads its not unusual. people rush to blame and replace the MC but often it simply gets better, There is likely a lot of slack in the rear system.
 

Cupr-o-matic

Active Member
Jan 2, 2010
10
0
Yeah the car's usable, my main concern is the long pedal travel. After the inital bite point (faint though it is) the pedal travels a further 2 inches or so before providing a significant resistance. However braking power is about 1/3rd of what I am used to.

Just for my own peace of mind, if I had damaged the servo I'm assuming that the pedal would be stiff to push where the vac assistance has been compromised? And the hissing would be constant indicating a vac leak?

I know individual circumstance has a lot to do with pedal feel, but can anyone (who has flipped seals) describe what the pedal feels like, if that makes sense?

The MOTs due next month and it wont go through as it is atm.

Cheers.
 

Ash-Kennard

why are you reading this?
Jul 31, 2008
286
0
portsmouth
It sounds to me like you definitely have air in the system.

If the pads are engaging and then you have a further 2" or so of movement at the pedal then that is likely air in the system as this is a compressible fluid. Whereas if the system was full of an incompressible fluid I.E. brake fluid, the bite point should be very close to the point of lock.

Sorry to have to say this but re-bleed the lot, see if you get an improvement.
 

anni25pd

Active Member
Jul 23, 2012
130
11
glasgow/ayrshire
They can be/are a nightmare to bleed at times! You say you have used an eesibleed do you mean the one way valve things where you still pump the brake pedal to push fluid through?
These systems NEED pressure bled.
 

Smoki333

Active Member
Dec 20, 2005
472
0
Wiltshire
I've just had a similar issue on my mk2 leon where I replaced my osr caliper including new pads both sides on the rears.
Bled the system with an ezibleed one-way valve, an my pedal just didn't have the bite it used too.
I was worried I had knackered the MC too, in the end my mechanic to pressure bleed the whole system including clutch which solved my issue.
Ezibleed just wasn't up to the job.

Plus remember if the rears where seized the pedal will feel a lot different when you fit working calipers...I got used to a solid pedal with a knackered caliper too now a softer pedal/more travel but is starting to bite better as time goes on.
 

747_727

Active Member
Apr 2, 2012
1,113
2
Essex
You might need to bleed it the old fashioned way by pressing the pedel with the bleed nipple open to get all the air out.
 

Muttley

Catch that diesel!
Mar 17, 2006
4,987
31
North Kent
You might need to bleed it the old fashioned way by pressing the pedel with the bleed nipple open to get all the air out.

This is *not* recommended, as it often leads to master cylinder seal failure.

Here is a (rather long) post I wrote a few years ago on Leon 1/Toledo 2 brake bleeding.

As far as bleeding goes, I can only give you the whole nine yards, based on experience plus the Haynes golf Mk.4 manual - which you should get hold of if you contemplate any more DIY. Haynes 4169, Golf and Bora 2001-2003.

Sorry this has turned into a bit of a lecture. But there are no safe shortcuts. Anybody reading this who finds a mistake - let me know, I'll repost it and/or get the moderators to make the change. Maybe even make it sticky if we can get all the details right.

Brake and clutch bleeding on the Golf Mk.4 platform

Hydraulic fluid should be changed at intervals of two years or less. The fluid deteriorates by absorbing water over time: mileage is not a factor. If it's more than two years since it was done, aim to change the whole contents of the system. I've not done this on a Mk.4 and don't know the quantity; the change is performed by bleeding in the correct sequence until the fluid coming out of the caliper changes colour. Use Dot 4 hydraulic fluid.

Always keep the fluid level in the reservoir at or near the full mark. If you let air into the system you have to start all over again.

You should run at least 0.25 litres of fluid from each caliper or slave cylinder. You will need more than 1 litre of fluid to complete a full bleed of the system.

It is not recommended to bleed by pumping the pedal, as there have been many instances of master cylinder seals being damaged using this method. If the master cylinder seals are damaged the master cylinder must be replaced.

I understand that people have succeeded in using the pedal method, without damaging the seals, by not pushing the pedal all the way to the floor.

The failure seems to be that the seals are caught and flipped round, so they fail to seal any more. I assume that there is a ridge worn in the master cylinder at the bottom of its normal stroke, which you go past once the resistance of the caliper or slave cylilnder is removed by opening a bleed nipple.

Use a pressure bleeding kit (Gunson Easibleed or equivalent).

The Clutch System
The clutch is fed from the same hydraulic reservoir as the brake system. Its master cylinder is fed from a pipe coming off the reservoir side, a small distance up from the brake connection which is in the bottom. This means that the clutch will fail first if you have a hydraulic leak. This can be a warning sign - if you get clutch disengagement problems, check the hydraulic fluid level.

The clutch will need to be bled if you change the slave cylinder on the gearbox or if air gets in by letting the level get too low. There is only one bleed nipple, at the slave cylinder end.

For cars with a five speed gearbox the slave cylinder is on the outside of the gearbox with an obvious bleed nipple.

The six speed gearbox has the slave cylinder integrated with the release bearing, inside the bellhousing and mounted around the gearbox input shaft. There is a bleed nipple on the outside of the bellhousing, close to the gearshift mechanism. Pressure bleed, then with the pressure kit still in place, push the pedal down and release it quickly to get any small bubble out of the long pipe to the middle of the bellhousing. Now bleed some more fluid through.

After bleeding, pump the clutch pedal up to pressure before starting the car again.


The Brake System

If you have any doubt at all about there being air in the master cylinder, bleed it first. There are two bleed nipples, one for each circuit. You should then bleed the front left and right calipers simultaneously, then the rear left and right calipers. This is to get any air out of the master-cylinder-to-ABS-unit pipes.

All the manuals say that the correct bleeding sequence depends on the type of ABS system you have installed.

The two possibilities are Mk.20 or Mk.60.

The Mk.20 unit is mounted flat, with the hydraulic unit on top, and has six hydraulic pipe connections on the left-hand face of the hydraulic unit. The two topmost are from the two halves of the master cylinder.

My 2001 Toledo TDI 110 SE had a Mk.20 unit.

The bleeding sequence for the Mk.20 unit is
Right (offside) rear
Left rear
Right front
Left front.​

This is furthest-to-nearest, as the ABS unit is on the nearside of the engine compartment.



The Mk.60 is mounted on the nearside wing with the hydraulic unit towards the engine. The two pipes from the master cylinder enter the uppermost side of the hydraulic unit and two pipes go to the rear brakes from the top of the hydraulic unit just below. The pipes to the front brakes are attached to the opposite side of the unit, and can only be seen from the bottom of the engine bay.

My 2004 Toledo TDI 150 Sport had a Mk.60 unit.

The bleeding sequence for the Mk.60 unit is
Left (nearside) front.
Right front
Left rear
Right rear​

I assume that this is because the unit is mounted vertically and the front brakes are fed from pipes attached to the lowest part of the unit.

If air has got into the ABS pump then VCDS or a dealers diagnostic computer may be needed to exercise the ABS unit and remove the air bubbles.
 
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