Valve Train Analysis

Valve Train Analysis - Engine Off - Valve Cover Removed
Check for damaged or severely worn parts and correct assembly. Make sure correct parts are used with the static engine analysis as follows:

Valve Train Analysis - Valve Springs
^ Check for broken or damaged parts.

Valve Train Analysis - Valve Spring Retainer and Valve Spring Retainer Keys
^ Check for correct seating of the valve spring retainer key on the valve stem and in valve spring retainer.
^ Check for correct seating on the valve stem.

Valve Train Analysis - Valves and Cylinder Head
^ Check for plugged oil drain back holes.
^ Check for worn or damaged valve tips.
^ Check for missing or damaged guide-mounted valve stem seal.
^ Check collapsed valve tappet gap.
^ Check installed valve spring height.
^ Check for missing or worn valve spring seats.
^ Check for plugged oil metering orifice in cylinder head oil reservoir (4.6L engine only).

Valve Train Analysis - Camshafts
^ Check for broken or damaged parts.
^ Check for loose mounting bolts on camshaft caps.

Valve Train Analysis - Camshaft Lobe Lift
Check the lift of each camshaft lobe in consecutive order and make a note of the readings.
1. Remove the valve covers.
2. Remove the spark plugs.
3. Install the Dial Indicator with Bracketry so the rounded tip of indicator is on top of the camshaft lobe.
4. Rotate the crankshaft using a breaker bar and socket attached to the crankshaft pulley bolt. Rotate the crankshaft until the base circle of the camshaft lobe is reached.





5. Zero the dial indicator. Continue to rotate the crankshaft until the (1) high-lift point of the camshaft lobe is in the fully-raised position (highest indicator reading).
6. To check the accuracy of the original indicator reading, continue to rotate crankshaft until the (2) base circle is reached. The indicator reading should be zero. If zero reading is not obtained, repeat the measurement.
7. If the lift on any lobe is below specified service limits, install a new camshaft, and new camshaft roller followers.
8. Install the spark plugs.
9. Install the valve covers.

Valve Train Analysis - Camshaft Roller Followers and Hydraulic Lash Adjusters
^ Check for plugged oil feed in the camshaft roller followers, lash adjusters or cylinder heads.
^ Check for collapsed hydraulic lash adjusters.

Excessive collapsed hydraulic lash adjuster gap can be caused by loose rocker arm seat bolts/nuts, incorrect initial adjustment or wear of hydraulic lash adjuster face, or worn roller hydraulic lash adjuster, push rod, rocker arm, rocker arm seat or valve tip. With hydraulic lash adjuster collapsed, check gap between the valve tip and the rocker arm to determine if any other valve train parts are damaged, worn or out of adjustment.

An incorrectly functioning hydraulic lash adjuster can be sticking, caused by contaminants or varnish inside the hydraulic lash adjuster. The hydraulic lash adjuster can have a check valve that is not functioning correctly, which can be caused by an obstruction, such as dirt or chips that prevent the check valve from closing, or a broken check valve spring. A hydraulic lash adjuster with a leakdown time out of specification can cause hydraulic lash adjuster noise. If no other cause for noisy hydraulic lash adjuster can be found, the leakdown rate should be checked and new hydraulic lash adjusters installed if found to be out of specification.

Assembled hydraulic lash adjusters can be tested with a commercially available leakdown tester to check the leakdown rate. The leakdown rate specification is the time in seconds for the plunger to move a specified distance while under a 22.7 kg (50 lb) load.

Air bubbles in the lubrication system will prevent the hydraulic lash adjuster from supporting the valve spring load. This can be caused by too high or too low an oil level in the oil pan or by air being drawn into the system through a hole, crack or leaking gasket on the oil pump screen cover and tube.