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 TM 55-1905-223-24-3
NOTE
Cylinder heads that have two valve springs for each exhaust valve require a
heavy duty spring guide at the top of the springs, and two spring wear plates at
the bottom of the springs.
d. Test the valve seats.
CAUTION
Never vacuum test a cylinder head with the injectors installed. Installing the
injectors can cause the valves to be out of alignment and will show leakage
during the vacuum test. When the cylinder head is installed to the cylinder
block, installing the injectors will not cause the valves to go out of alignment.
(1)
Use the valve vacuum tester to check the seal between the valve and the valve seat.
(2)
Be sure that the valve and valve seats are clean and dry.
(3)
Put the vacuum cup over the valve. The O-ring in the cup must make a seal on the cylinder
head around the valve.
(4)
Turn the shutoff valve to the open position. Hold down on the pushbutton to stop the vacuum
pump.
(5)
Operate the vacuum pump until the vacuum gauge indicates between 18 to 25 in. Hg (457 to
635 mm Hg).
(6)
Turn the shutoff valve to the closed position. Release the pushbuton to stop the vacuum
t
pump.
(7)
Check the time for the gauge to indicate a decrease in vacuum.
(a)
Start timing when the gauge indicates "18".
(b)
Lightly hit the valve stem with a soft hammer.
(c)
Check the connections on the vacuum tester for leaks by starting the pump and holding the cup
against a smooth surface. A decrease in vacuum indicates a loose or leaking connection.
(8)
If there are no loose or leading connections on the tester, check for leaks between the valve
seat insert and counterbore.
(a)
Apply a coat of grease to the outside diameter of the insert to make a grease seal between the
insert and the counterbore.
(b)
Vacuum test and inspect the grease seal. A break in the seal indicates a leak between the
insert and counterbore.
(c)
Stake the valve seat insert and vacuum test for leaks.
4-53
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