Any excess sealant could be ingested by the pump, causing its destruction. Airborne recommends a sparing application of silicone spray on the threads, but nothing more. Make certain that the vacuum system is scrupulously clean before installing a new pump. Always blow out the hoses with compressed air, replace the central vacuum filter and the regulator's foam garter filter with new ones, and check the regulator seat for trapped carbon fragments. Troubleshooting Tips Troubleshooting the vacuum system is a process often misunderstood by mechanics.
Most shops lack the proper test equipment, and rely on the cockpit vacuum gauge.
But the cockpit gauge is a poor troubleshooting tool. Furthermore, it's not uncommon for cockpit gauges to be way out of calibration. For example, the vacuum gauge on one single-engine aircraft was found to require 9 in. Hg. of vacuum to indicate 5.0 in. The vacuum pump, forced to provide 10.5 in.