Wrangler 4WD L4-150 2.5L VIN P MFI (1998)
Vacuum Check Valve HVAC: Testing and Inspection
1. Remove the vacuum check valve. The valve is located in the (black) vacuum supply tube at the intake manifold vacuum tap.
2. Connect the test set vacuum supply hose to the heater (natural color) side of the valve. When connected to this side of the check valve, no vacuum
should pass and the test set gauge should return to the 27 kPa (8 in. Hg.) setting. If OK, go to Step 3. If not OK, replace the faulty valve.
3. Connect the test set vacuum supply hose to the engine vacuum (black color) side of the valve. When connected to this side of the check valve,
vacuum should flow through the valve without restriction. If not OK, replace the faulty valve.
