Without VAG 1551

REQUIREMENTS

- Engine coolant temperature at least 176°F (80°C).

- All electrical consumers (including A/C) switched OFF.

- Radiator fan must not run while performing tests

- Vacuum connections tight and without leaks.

- Vacuum hoses not pinched or plugged.

Testing Vacuum Diaphragm

EGR Valve Testing:

- Disconnect vacuum hose from EGR valve.

NOTE DO NOT run engine during this test.

- Using hand vacuum pump, apply vacuum to EGR valve.

- Vacuum should hold without dropping

- If vacuum drops, or will not build up:

^ Check hose connections for leaks

^ Check vacuum pump operation

^ If pump and lines are OK, replace EGR valve

Testing Exhaust Gas Flow

- With the engine running, apply 400 mm (16 in.) Hg of vacuum to the valve and observe the results:
a. The engine speed must drop while applying vacuum.

b. The engine speed should return to normal after releasing vacuum from the valve.

- If the engine speed does not change, the EGR the passage could be blocked.

- Check the EGR valve, lines, and ports in the intake and exhaust manifolds for blockage and clean out or repair as necessary.