Boost is a precious commodity and you don’t want to lose any of that horsepower-generating pressurized air to leaks in the system. Even if you’re fairly confident that you’re pretty air tight, it’s still a good idea to double check before getting a tune. With a few parts you may have lying around the garage, find those sneaky boost leaks and make all the power you’re supposed to with this El Cheapo DIY boost leak tester!
In order to build the right size leak tester, start by measuring the diameter of your turbo inlet. You can identify the inlet side if you see the compressor wheel. You’d test at this point because everything after the turbo’s inlet normally gets pressurized.
Get a rubber coupling that will fit your turbo inlet based on your measurements as well as PVC cap to plug one end of the coupling. Drill a hole just big enough to fit a tire valve stem through your PVC cap and use some epoxy glue around the edges of the hole to be sure it’s air tight. Just don’t get any glue in the valve stem!
Tighten a hose clamp around your rubber coupling to grip the PVC cap as tightly as possible. This end could fly off when you pressurize your system so use two hose clamps side-by-side if you can. If you have an extra boost gauge, hook it up so you can monitor the test pressure in the system. Otherwise you’ll need a friend to watch your interior gauge for you.
With your boost leak tester complete, it’s time to stop those leaks! Use a hose clamp to attach your tester to the inlet of your turbo and use either a tire pump or air compressor to pressurize the system through the tire valve stem. You don’t need much PSI to test! Start with 6 psi and work up from there but never exceed the boost your car runs normally. A good safety measure is to regulate your air compressor down so you don’t accidentally blow out any seals.
A leak will be pretty obvious and make a loud hissing noise. If your system is not holding any pressure then you have a major leak somewhere. If all is silent then you’re ready for your tune and then some pavement thrashing fun!
For more examples, check out the DIY Boost Leak Test thread on VWvortex, boost leak test and leaking turbo symptoms – how to fix thread on MyTurboDiesel, or DIY boost leak tester thread on BenzWorld.