Ensuring that your turbo system is free of boost pressure leaks is an important step in preventative maintenance. It allows you to diagnose the numerous problems that can arise from a vacuum leak, as well as reveals faulty seals and gaskets in the turbo and intercooler system. Though such problems can be diagnosed via ECU data logging, a physical boost pressure test is the quickest and most uncomplicated way of checking your turbo system's integrity.
Purchase a pressure tester device. These are hand-powered air pumps with pressure gauges attached. Most pressure testers are intended for use on vehicle radiators, so you'll also need a rubber adapter to attach the tester's hose to the turbo's inlet. Both the pressure tester and adaptor can be purchased from most automotive parts dealers.
Detach the turbo's intake from the turbo inlet. The intake doesn't need to be completely removed, just disconnected from the turbocharger. The process for disconnecting the intake will vary between makes and models. Most often, it requires using a socket wrench to loosen the clamp ring that holds the intake onto the turbocharger. Once loose, simply lift the intake out of the way so that the pressure tester can be fitted.
Attach the pressure tester to the turbo's inlet. This is done by sliding the rubber intake adapter over the turbo's inlet, then tightening it in place with a clamp ring. Attach the other end of the rubber adapter onto the pressure tester's hose likewise with a clamp ring.
Pressurize your turbo system with the pressure tester's hand pump. You want to build the pressure to that which your turbo produces to ensure the reliability of all seals. Pump the pressure tester until its gage reads the desired PSI, then watch the gage to see if the pressure begins to drop. If so, your turbo system has a boost leak. In this case, keep your system pressurized and listen along all piping and seals for hissing air. When you've located the pressure leak, fix it by tightening the necessary fittings, and replace any blown seals if needed.
