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4 pot brakes Vs master cylinder size.

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4 pot brakes Vs master cylinder size.

Post by dirtytorque on Wed Feb 03, 2010 3:46 pm

Ok so I bled the system again....

I shunted shedloads of fluid through each corner with the rear valve regulator fully actuated.
I have bled the whole system before without too much trouble using the same equipment so I must conclude that it is because the new components i have introduced into the system,namely the wilwood brakes as I have tried every corrado brake bleeding method ever posted on the internet. Smile
Not I went against my better judgement and sold my g60 standard front brakes so I have to see this through.
I have reaserched on vortex and read numerous threads about people running 22mm Master cylinder with various 4 pot brakes fine so I'm stumped.
I'm going to purchase a VR mastercylinder as I understand it is slightly larger and maybe go from there.Has anyone upgraded their bakes and then had to upgrade their MC aswell?
I remember JMC saying that his porshe brakes weren't as sharp as maybe he was expecting although at least his are functional.
I'm not sure mine would get through an MOT tbh.
Maybe my MC is just faulty...
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Re: 4 pot brakes Vs master cylinder size.

Post by mrbeige on Thu Feb 04, 2010 1:34 am

There must be something else up. I can't beleive that the standard MC with the Willwoods would have so much trouble. What size MC does an S2 run? Gav (peanut) might have one of those floating about, if that is any help?

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Re: 4 pot brakes Vs master cylinder size.

Post by jmc on Thu Feb 04, 2010 3:27 am

Yeah it is an odd one this. Common sense says that you would need a bigger master cylinder given the bigger pistons size. One thing to add with mine I'm running ABS, which I would assume would have some impact on feel under this circumstance. However I've never been able to get a definative answer.
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Re: 4 pot brakes Vs master cylinder size.

Post by Yandards on Thu Feb 04, 2010 10:31 am

I did post up all the possible options for bleeding ABS cars from the VW workshop manual so if it aint working then something is wrong.

The mk 2 Golf boys don't seem to have the same problem so I can only conclude that something else must be up with your braking system aside from the Willwoods that is causing this.

Have you considered by-passing the ABS unit temporarily by using brake line fittings to see if this cures it?

If not then I am more than happy to try the willwoods on either of my non-ABS cars (for the purpose of science obviously Smile)

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Re: 4 pot brakes Vs master cylinder size.

Post by dirtytorque on Thu Feb 04, 2010 10:57 am

Yandards wrote:I did post up all the possible options for bleeding ABS cars from the VW workshop manual so if it aint working then something is wrong.

The mk 2 Golf boys don't seem to have the same problem so I can only conclude that something else must be up with your braking system aside from the Willwoods that is causing this.

Have you considered by-passing the ABS unit temporarily by using brake line fittings to see if this cures it?

If not then I am more than happy to try the willwoods on either of my non-ABS cars (for the purpose of science obviously Smile)

Yup something is up,i'm doing something wrong or there is a faulty component in the system.
Lol,I might take you up on sending them to you.
I have another MC coming shortly which I will fit and see.If that don't work then fluck knows what i'll do. Smile
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Re: 4 pot brakes Vs master cylinder size.

Post by jmc on Thu Feb 04, 2010 1:30 pm

You're more than welcome to come and feel the brakes in mine if you're over this way. Atleast then ou have a comparison with how yours feel.
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Re: 4 pot brakes Vs master cylinder size.

Post by dirtytorque on Fri Feb 05, 2010 3:31 am

cheers Jonathen,i'd be very surprised if yours felt like mine tbh.
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Re: 4 pot brakes Vs master cylinder size.

Post by dirtytorque on Tue Feb 09, 2010 1:39 pm

so help me out chaps.

With engine running I can definitely hear a slight whshhh when i depress the brake pedal.That ain't right surely?
Do break servo's go.Seems to be coming from that direction.
Or faulty MC p'haps?I'm thinking maybe MC.
When I depress he pedal it is fairly squidy and makes above noise.If i keep pumpoing it firms up.If I then leave a while and then pump it again the cycle repeats.
I think I'm going to strip that end of the brake system down tomorrow.
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Re: 4 pot brakes Vs master cylinder size.

Post by mrbeige on Tue Feb 09, 2010 2:18 pm

How good is the vacuum provided by the engine to the servo?

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Re: 4 pot brakes Vs master cylinder size.

Post by dirtytorque on Tue Feb 09, 2010 2:44 pm

seems alright..How would i know?
I have normal vac levels at idle...
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Re: 4 pot brakes Vs master cylinder size.

Post by Yandards on Wed Feb 10, 2010 2:46 am

Going to dive in here about the servo.

With the fault you have Rob (long squishy pedal) it is never going to be the vacuum operated servo assistance. If you ever drive a car with no servo then the brake pedal works the same as usual (progressive) you just need to push harder. Your fault is a soft pedal, so it's not the servo.

I would go with a new MS, the pumping action to firm them up sounds exactly like the sort of symptom I would expect for worn seal on the MS; you have no leaks from the caliper seals so that is the only other bit in the system bar the ABS unit.

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Re: 4 pot brakes Vs master cylinder size.

Post by dirtytorque on Wed Feb 10, 2010 3:46 am

/\/\/\

should there be some evidence once the MC is off?
i.e some fluid in the servo ?
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Re: 4 pot brakes Vs master cylinder size.

Post by Yandards on Wed Feb 10, 2010 4:11 am

Possibly but unlikely. The servo is only mechanically connected to the MS not hydraulically.

Given the fresh fluid through the system and new calipers up front it is no suprise that your MS has given up the fight.

I assume that the ignition is off when you are doing this, if not have you tried it with the ignition on (but not running) to see if the problem is still there?

A dodgy MS would also explain why the system is not bleeding correctly.

You should be able to strip the MS down once it's off and have a look at it, IIRC there is a circlip holding it all together on the servo end. Unfortunately VW don't do a seal kit for it as they say it's not a repairable part.

To check the servo is ok (and I am sure it is) run the car and then turn it off. Depress the brake pedal several times until the servo assistance is gone (pedal goes heavy) and then depress around halfway and hold. Start the engine and the pedal load should reduce slightly as the servo assistance kicks back in.

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Re: 4 pot brakes Vs master cylinder size.

Post by dirtytorque on Wed Feb 10, 2010 4:25 am

Thanks for all the help. Smile
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Re: 4 pot brakes Vs master cylinder size.

Post by dirtytorque on Fri Feb 12, 2010 11:28 am

oh what a tool I am. Rolling Eyes
Razz
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Re: 4 pot brakes Vs master cylinder size.

Post by dirtytorque on Wed Feb 17, 2010 1:39 pm

So i'm going to fit new braided lines at the weekend.
Is a dot5.1 upgrade worthwhile or not?????

weekend toy street use car.
Thanks.
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Re: 4 pot brakes Vs master cylinder size.

Post by mrbeige on Wed Feb 17, 2010 1:54 pm

Never done it myself, but have always been told that if you were to change the fluid, better to stick dot5.1 in there.

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Re: 4 pot brakes Vs master cylinder size.

Post by ctwg60 on Fri Mar 05, 2010 4:55 am

If you need original callipers, I have a pair of 4 year old 20,000 mile VAG items in the garage. £50 they're yours! Laughing

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Re: 4 pot brakes Vs master cylinder size.

Post by dirtytorque on Fri Mar 05, 2010 2:31 pm

nah,all sorted now.I'll be sticking with the 4-pots.
User error.Don't ask. Smile

Not lost your touch though I see.Still quick to spot a potential sale. Wink
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Re: 4 pot brakes Vs master cylinder size.

Post by ctwg60 on Fri Mar 05, 2010 2:36 pm

What was it then? I'm dying to know!

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Re: 4 pot brakes Vs master cylinder size.

Post by dirtytorque on Fri Mar 05, 2010 2:51 pm

Smile

I only bleed two pots a side.
I thought the outer bleed nipples bled both sides of the caliper.I was bleeding them with the wheels on see.
As soon as i took the wheel off and saw the other nipples it became obvious what the problem was. Embarassed
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Re: 4 pot brakes Vs master cylinder size.

Post by ctwg60 on Fri Mar 05, 2010 3:15 pm

Laughing

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Re: 4 pot brakes Vs master cylinder size.

Post by dirtytorque on Fri Mar 05, 2010 3:16 pm

Very Happy
Indeed.
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Re: 4 pot brakes Vs master cylinder size.

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