# MK3 Jetta - Pressure then no brake pressure



## Xs Studio (Nov 1, 2006)

I've been having issues with my brakes for a week now after upgrading the rear brakes to the aluminum MK4 setup.

All lines were power bled, my brake lines and master cyclinder are not leaking. I get brake pressure to three wheels Left Front, Right Front , Right Rear but not Left Rear. Eveytime i bleed the left rear i loose brake pressure to the right front.

So i said OK let me get the pressure back up to the three wheels and see if i have any braking power. Nope as soon as i turn the car on and hit the brakes it goes all the way down to the floor.

My mechanic bench bled the master cyclinder and assured me there was adequate pressure at the master cyclinder. We power bled the car again and only got brake pressure to two wheels this time around: Left front and Right Rear. He checked the master cylinder again and there was adequate pressure at the master cylinder and it was not leaking.

I installed the old MK3 rear brakes but the issue persisted.

At this point im ordering a new master cylinder but he seems doubtful it will work so im asking you guys would the brake pressure regulating valve cause this issue ?


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## greyhare (Dec 24, 2003)

Does the car have ABS?


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## germancarnut51 (Mar 23, 2008)

How did your mechanic determine that there was adequate pressure at the master cylinder? Did he remove the brake lines to the two non-working brakes (one at a time) attach a pressure gauge, and apply the brake pedal to monitor the brake pressure?

If the car doesn't have ABS, I'd say what you need is a new master cylinder. Meyle makes a good alloy bodied replacement master cylinder (non ABS cars) for about $45.


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## Xs Studio (Nov 1, 2006)

greyhare said:


> Does the car have ABS?


No it doesnt


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## Xs Studio (Nov 1, 2006)

germancarnut51 said:


> How did your mechanic determine that there was adequate pressure at the master cylinder? Did he remove the brake lines to the two non-working brakes (one at a time) attach a pressure gauge, and apply the brake pedal to monitor the brake pressure?
> 
> If the car doesn't have ABS, I'd say what you need is a new master cylinder. Meyle makes a good alloy bodied replacement master cylinder (non ABS cars) for about $45.


He didnt use a pressure gauge - he unhooked the brake line and had me press down on the brake to see if there was adequate pressure. Brake fluid spurted out at the master cylinder and the calipers each time i hit the brake thus he stated there was adequate pressure.

Oooo and yeah i ordered the Meyle master cylinder stay away from the KMM master cylinders as they do not have the screw holes on the side where the reservoir locks into. 

And thanks for your help guys


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## germancarnut51 (Mar 23, 2008)

When we ordered our first Meyle master cylinder, the KMM came up first on the top of the page, and it was dirt cheap.

I took one look at the thing and turned away. Not saying that it might not work, but in the catalog photo, the part looked so crudely made that I said there's no way I'd order it, and if someone gave it to me, I'd toss it in the first recycling bin I came across.


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## greyhare (Dec 24, 2003)

Xs Studio said:


> He didnt use a pressure gauge - he unhooked the brake line and had me press down on the brake to see if there was adequate pressure. Brake fluid spurted out at the master cylinder and the calipers each time i hit the brake thus he stated there was adequate pressure.
> 
> Oooo and yeah i ordered the Meyle master cylinder stay away from the KMM master cylinders as they do not have the screw holes on the side where the reservoir locks into.
> 
> And thanks for your help guys


According to the Bentley manual a gauge capable of reading over 2300 psi is needed to test the system. Seals that work fine at 15 psi may not work at 2000 psi.


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## germancarnut51 (Mar 23, 2008)

Xs Studio said:


> He didnt use a pressure gauge - he unhooked the brake line and had me press down on the brake to see if there was adequate pressure. Brake fluid spurted out at the master cylinder and the calipers each time i hit the brake thus he stated there was adequate pressure.
> 
> Oooo and yeah i ordered the Meyle master cylinder stay away from the KMM master cylinders as they do not have the screw holes on the side where the reservoir locks into.
> 
> And thanks for your help guys



Have you actually seen a KMM? 

Do they look as bad as as they do in the photos?

I wouldn't be that worried about not having the locking pin on the reservoir (none of my Porsches or Ford Wagon have them), I'd be more worried about the how it works.


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## Xs Studio (Nov 1, 2006)

germancarnut51 said:


> When we ordered our first Meyle master cylinder, the KMM came up first on the top of the page, and it was dirt cheap.
> 
> I took one look at the thing and turned away. Not saying that it might not work, but in the catalog photo, the part looked so crudely made that I said there's no way I'd order it, and if someone gave it to me, I'd toss it in the first recycling bin I came across.


I learned my lesson. If something is too good to be true it usually is.


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## Xs Studio (Nov 1, 2006)

greyhare said:


> According to the Bentley manual a gauge capable of reading over 2300 psi is needed to test the system. Seals that work fine at 15 psi may not work at 2000 psi.


Thanks it ended being a build of dirt at the bottom of the reservoir and in the master cylinder itself. I dont know how dirt got in there but it was significant amount of sludge. 

I changed the master cyclinder today and im good to go. Wish i had taken pictures of the sludge build up


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## Xs Studio (Nov 1, 2006)

germancarnut51 said:


> Have you actually seen a KMM?
> 
> Do they look as bad as as they do in the photos?
> 
> I wouldn't be that worried about not having the locking pin on the reservoir (none of my Porsches or Ford Wagon have them), I'd be more worried about the how it works.


My reservoir actually needs the lock pin - as it doesnt sit on the master cylinder securely without it.


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## Xs Studio (Nov 1, 2006)

*Thanks for the help*

thanks for the help everyone


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