Finding Vac Leak

[sundown]

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2003 VW Passat 1.8T

I have the obvious sound of a vacuum leak coming from my drivers side front wheel area. Car ran fine when i got up this morning and headed to work. Got off work and i noticed a funny idle (low about 750). Any-who, none of the obvious culprits from the topside of the engine are obviously damaged. What would be coming from the drivers side front wheel area?

Whats the best way to track down a vacuum leak? I seem to remember someone saying something about using some propane (maybe) and letting it flow into the cracked/broken line which would cause the engine to stumble and give you a decent idea to where the leak is. Just want to confirm it is propane before i blow up my engine.

Thanks all for the help! Merry Christmas and Happy Holidays to everyone!

 

[Ken Ford]

Don't use propane. Carb cleaner works but not near as explosive.

 

[haole396]

It's a little time consuming but any "garage guy" can use a pair of needle nose pliers, and one at a time pinch off rubber (not the plastic) hoses. If there is a vacuum leak, the idle will change or the noise should go away giving you a general idea of where to look. If I had to take a guess as to what is in the left front area it could be an EVAP canister or vacuum reservoir.
Good luck!

 

[streetglide08]

I know on a 1.8T jetta the turbo is situated in that area. Is your boost working okay.

 

[CADFather]

Up in that area of the car, I'd look long and hard at the vacuum assist on the brake booster. As was mentioned take some carb cleaner in a spray can and spray the vacuum hoses with it, while the car is running. When the idle changes, track down the lines one at a time and find which one it is.

CAD

 

[jsquared]

A vacuum leak will usually cause your car to idle higher, not lower, as it pulls more air than is metered into the intake tract. Like someone else mentioned before, when you are in boost does your car feel normal or like it lost power?

Also, Ive never had much luck looking for vacuum leaks using carb cleaner. I have tried numerous times and never heard it change the idle or make the engine stumble no matter how much I sprayed, I just ended up with a soggy engine bay. I have had much better luck using soapy water in a spray bottle.

You have a turbo, which means at 1500rpm or so you should be reaching 0psi or very slight positive pressure. Spray water on your intercooler fittings and vacuum connections while turning the throttle body open and keeping the revs up to around 2k. This should make any "vacuuum" leaks blow bubbles through the soapy water.

Or, take it to a shop that has a smoke machine and do it the right way, should only cost you an hour's labor or so.