ALH Brakes fade sometimes and Boost issues....?

Vehicle info..... 2002 Jetta TDI 192k miles

Hey guys, I recently started noticing that my brakes will occasionally fade as if they are overheated; though I know for a fact they aren't. It's like I'm losing my power brakes. Also, sometimes I feel like my car isn't making much boost and other times it's boosting just fine (No boost gauge so I can't give you exact numbers). Last thing, when I'm driving my car and I pull up to a light, I can faintly notice something that feels like a misfire or like my clutch is chattering, but it's not. Don't know if all of these issues are related....
My first thought was that my vacuum pump is going out and upon further visual inspection I saw there is a decent leak seeping out from under the vacuum pump.
I have a few questions......
1. Should I replace the entire vacuum pump or just the seal?
2. Is there somewhere else I should look for a vacuum leak?
3. Could a failing vacuum pump cause these issues or am I looking in the wrong place?

Thanks, as always!
-Fred-

sounds like a classic vacuum leak to me, but it also sounds intermittant, which would make it very hard to find.

It explains both the brake issues (vacuum brake booster) and also I'm not sure how familiar you are with the car, but the turbo is actuated via vacuum. More vacuum, more boost... vacuum leak, no boost.

I would not suspect the vacuum pump right away, I would check for leaks in the lines first. The vacuum pumps are known to leak oil, but I dont think that it effects actual function. In fact, my vacuum pump is sealed shut with JBweld to stop the leaking, but it produces vacuum just fine. I've also heard that the big Oring that you get with an oil filter is a good fit for the inside of the vacuum pump. that might be worth looking into it before you permanently seal it like I did

The stock vacuum line is very prone to cracking in old age and dryrot. Also the hard plastic line that goes from the vacuum pump to the brake booster ive heard of splitting and causing intermittant vacuum issues.

As for the clutch, the stock clutch has a dual mass flywheel, and although I replaced mine before it failed, I think they can make a chattering or clunking when it starts going bad. Not sure if thats the noise you're hearing though.

Pretty familiar with the car. I'm aware of the vacuum actuator for the turbo. I'll have to do some more digging through the vacuum lines to see what I can find. My TDI buddy just suggested I wiggle the hose off of the pump and hook up a vacuum pump to see if I can read a leak.

You can by a new seal for that pump from idparts. Install it and most if not all of your vacuum problems will go away.

It's very common for the plastic hose from the pump to the brake booster to crack on the back side on the inside bend where it's hard to see it.

jettawreck said:

It's very common for the plastic hose from the pump to the brake booster to crack on the back side on the inside bend where it's hard to see it.

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This. Check the hose first. Also the fitting on the vacuum pump sometimes develops a leak where it comes out of the pump.