? about vacuum system...sometimes it feels like no power brakes...

[midairmark]

I seem to be having a brake-vacuum issue... every once in a while it feels like I do not have power brakes... very hard to stop. If I leave my foot on brake pedal with good amount of foot pressure, it feels like the pedal wants to go to the floor. There is a sound of vacuum leaking too, when I hold pressure on brake pedal (while car is stopped), but it always doesn't do it.

With about 253k miles, I've never touched the vacuum pump or brake booster or accumulator or anything that leads to the system. I've also never changed any vacuum lines.

Where is a good place to start to diagnose or is there a common issue that anyone else has experienced?

Car is 01 Jetta.

Thank you for the help as always!

 

[P2B]

Check the vacuum line to the brake booster and the grommet where it connects to the booster. Known failure points.

 

[Gothmolly]

I get this a lot. Mechanic replaced the booster about 100k ago, problem is back.
Learn to downshift, the brakes might not be there when you need them.

 

[Black00Jetta]

Chech the connection on the vacuum pump first. Use a mity vac and measure while you hold the nipple. When I checked mine, I was pushing the connector that was loose in so I was making it seal. When I pulled it out I lost vacuum. I had already replaced the vacuum booster (pia) then the big connector from pump to booster before finding my problem was the vacuum pump nipple.

Hope this helps.

 

[akjdouglass]

How loose does that nipple have to get before causing issues? I was checking things out recently and thought I had a loose hose clamp, but it was the nipple spinning at the housing.

 

[Nevada_TDI]

It does not have to get very loose to affect brakes and turbo operation. Get a cheap vacuum gauge, and check vacuum from pump to solenoid farthest from vacuum pump. Solenoids will crack and lose vacuum from one one side to the other.
After crimping vacuum pump nipple, I still had vacuum issues so I bypassed all but critical solenoids and 200k miles later I still have 25" of vacuum at idle.