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Discussion Starter #1
When I bought this car one year ago I had the brakes serviced (changed pads, resurfaced discs and had calipers rebuilt) un unfortunately we didn`t look at the master cylinder, so it went down and some brake fluid entered the booster and it went down.

I took the car to the same shop that made my brake service for repair, I was charged some good money for the job, but as it was an old car I had no complaints. But now, I`ve had trouble with my booster. The check valve went wrong and fuel entered the booster distroying it, so now I have to change the booster again!!

I told these guys if they checked the "check valve" and they said NO, that it usually works fine, that there is no way to tell if it would go down or not. But they didn`t tell me that (if so I would have changed it imediately) so now I have to pay again. I told them that they must check that valve as part of the procedure of a brake booster rebuilt but they were not going to give me the point on it.

Can someone tell me the life expectancy of this valve? how often does it need to be replaced? this guys were lazy? (I think they were)

Thanks.
 

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What exactly are your brakes not doing? The reason I ask is that mine are acting up after a year as well. I thought my front calipers were tired, but after replacing them the pedal is still soft, and the car doesn't stop well at all. A year ago I replaced the booster, the master cylinder, all the flex lines, the brake pads, and the check valve. Back in July the front brakes kept locking if I applied them while rolling with the wheels turned. I could never get them to do it some place where I could take a closer look. Eventually I came to the conclusion that the front calipers only were hanging up. I replaced them on Friday, drove the car yesterday (with a soft pedal) and they locked on me again. A second push of the brake pedal will release them, but despite my replacing the front calipers, the problem is still here.

Now I'm thinking its a booster issue.

Will
 

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Discussion Starter #3
Will,the only way I can figure out that you can get a harder pedal is to instal braided stainless steel brake lines since they do not expand under pressures resulting in a firmer pedal feel.

My brakes were ok until the check valve went wrong and the booster died, resulting in no power assistance on the brakes, so the pedal was extremely hard. They´ve replaced the booster and the check valve and everything is fine except for the pedal feel, its different. So in the future I will instal the braided stainless steel brake lines.
 

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I have the braided s.s. lines. They went on shortly after the car went back on the road.

Will
 

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Ennio wote: "unfortunately we didn`t look at the master cylinder, so it went down and some brake fluid entered the booster and it went down"

I suspect that exposure to brake fluid is what destroyed your booster. A common failure mode on hanging pedal Alfas is that the seal at the back of the master cylinder fails, and the vacuum in the booster draws brake fluid into the booster. For some reason, the booster's diaphragm is made of a material that brake fluid will dissolve or otherwise damage. So, it is not uncommon for a booster to die a year or so after the MC has been replaced.

Check valves usually do last forever. Are you sure that 1) your's failed, and 2) its failure is what caused the booster to fail?
 

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Discussion Starter #6 (Edited)
Jay,

The MC was not cheked the first time, so when the seals failed the fluid entered the booster destroyig it. Yes, we test the check valve and it was wrong, we installed another valve as well as another ATE booster which they told me was from a Vw Passat and has the same diameter. So far so good.

The only thing that could have killed the booster was the fluid from the engine that came through the failing valve.
 

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Brake thoughts;

BlpltGTV: It may be the booster/pedal linkage is not adjusted properly. Some pressure is holding the brakes on, pressing a second time drains some pressure and releases the brakes. If that is the case it must be pretty close to working. The linkage can just be screwed in or out. You will have to disengage the linkage. Quite likely if the booster has been swapped out.

Ennio: (thanks for the pm) the check valve should be pretty bullet-proof. They do however get clogged up with crap in the plenum. Cleaning them out with carb cleaner works wonders. Yours probably just stuck open.

If you have access to a Mity-Vac or similar you can check the valve. Even sucking on it from the booster side than blowing should test it. May want to clean it first!

Good thing with the Mity-Vac is checking vacuum. Should run minimum of 18 in/hg at idle. Pressing the brake a few times should not drop the vacuum noticably.

I have 2 GTV6's and they are both marginal on the booster. Actually, one is scary :eek: the other I have a lot more confidence in.
 
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