First Plenum Pull posted by boostlv on September 05, 2012 at 08:09 AM
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Yeah the coolant lines and the bypass can all be done with the plenum off. The EGR is possible, but extremely challenging without dropping the transmission or pulling the engine.
Try a coolant pressure tester (is that what you meant by coolant tester?) You can pressurize the cooling system from the radiator fill cap and watch for where coolant shoots out behind the plenum. Just make sure to not overpressurize the cooling system or you can damage it. 10-15psi is a good safe bet for this kind of troubleshooting.