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Discussion Starter #1
I'm looking for a little advice on a 2.4 98 reg T4 with brake problems. A while back the brakes seemd to fail but infact it was just that the servo assitance just suddenly dissappeared. The brakes work intermittently as if there is sometimes a vacuum and at other times none. When there is none, the brake pedal is very hard and the power in the brakes is very weak. I have replaced the vaccum pump (scrap yard job) but the problem persists. I have done all the usual checks, it is nothing to do with the discs, pads or brake fluid system but seems to be related to the pump, the servo or the hose but i can't find any leaks anywhere. When i remove the vacuum hose from the servo there is no suction from the hose and yet when driving at a steady speed the brakes will work as normal on the first compression of the pedal as though there is some kind of vaccum in the servo. This vacuum is lost if the pedal is then compressed a second time but then seemes to build up again after another steady run.
I've trawled through all the threads but so far nothing seems to fit. I don't have the loud rattle or clatter coming from the vacuum pump that many descibe and pumping the pedal does nothing to help. Each time i have removed the pump there is a little oil in it but i imagine that's normal from the movement of the push rod? I'm keen to avoid forking out for a vacuum pump only to find it's not the cause, it seems unlikely.... Any help much appreciated! :) Apologies for the long thread, trying to be comprehensive! :)
 

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I sounds like the one way valve is bust. I'm thinking as you release the pedal it's sucking air back into the servo. Does the pedal soften up again after a few seconds? I'd try it first anyway. Should be cheap enough from a breakers. Think a MkIV golf etc would have the same part. Double check the hose too particularly where it joins the valve and servo. I know mine is split there and taped up at the moment.
 

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Discussion Starter #3
Thanks for that, it's the one thing i haven't checked yet.... but with the engine running i don't seem to be getting any suction from the vaccuum pump if i remove the vacuum hose? And yet as you say, the pedal does become soft again after a few seconds, the brakes do return and it seems there is a sucking or hissing sound from the pedal....
I'll try it and see! Will post an update once i've tried. Thanks :)
 
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