Best way to find vacuum/air leaks

[Cannman07]

Hi, just wondering what people do to find vacuum/air leaks around the valley gaskets and intake manifold? I think I have a tiny leak but haven't been able to find it. Series II VX S.

 

[JSVSouth]

Easiest way to diagnose inlet manifold leaks is to spray brake cleaner around the area while the engine is running. If you notice an RPM increase when spraying at a particular area, chances are you have a leak. If valley/inlet gaskets haven't been replaced recently, it probably worth doing anyway.

 

[vc commodore]

Valley cover gaskets if leaking will generally have coolant leaking out of them..

 

[Fu Manchu]

Easiest way to diagnose inlet manifold leaks is to spray brake cleaner around the area while the engine is running. If you notice an RPM increase when spraying at a particular area, chances are you have a leak. If valley/inlet gaskets haven't been replaced recently, it probably worth doing anyway.

That method is very hit and miss. Only a small percentage of the area under vacuum would be tested.

Smoke testing is the bench mark method. It finds the tiniest of leaks. The most difficult to find, with positive id of the exact location, making cause for the leak easier still.

EVAP leaks are also a source of vacuum leak and spraying a bit of combustible aerosol won’t stand a chance of finding them.

 

[krusing]

As @Fu Manchu explains,

Smoke Test is the only way !,
I purchased a smoke machine some time back, for testing my L67 as it was idling a bit high after the LIM gaskets replacements,
Found some of the existing rubber fittings, and hoses were perished,
and has been a very handy unit,
I have done a few tests since on the following area’s -,
VACUUM leak
PCV Leak
Exhaust Leak

Finds them EVERY time.

 

[Fu Manchu]

I made mine.

Pipe cleaners, pop sticks, googly eyes, glitter and some PVA wood glue.

 

[Cannman07]

Thanks, I'll try and get my hands on a smoke machine.