Leakdown Test

DESCRIPTION
Test the assembled hydraulic valve tappets with a Hydraulic Tappet 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. Test the valve tappet as follows:

PROCEDURE

NOTE:
Mixing Components
Do not mix parts from different hydraulic valve tappets. Parts are select-fitted and not interchangeable.

Testing Fluid
Hydraulic valve tappets cannot be checked with engine oil in them. Use only the testing fluid. Do not use kerosene or any other fluid

1. Disassemble and clean the hydraulic valve tappet to remove all traces of engine oil.
2. Place hydraulic valve tappet in tester with plunger facing upward.

NOTE: The fluid can be purchased from the tester's manufacturer. Using kerosene or any other fluid will not provide an accurate test.

3. Pour hydraulic tester fluid into cup to a level that will cover hydraulic valve tappet.
4. Place 7.94 mm (5/16-inch) steel ball provided with tester in plunger cap.

NOTE: Use the center mark on the pointer scale as Stop Timing point instead of the original Stop Timing mark at top of scale.

5. Adjust length of ram so pointer is 1.59 mm (1/16 inch) below starting mark when ram contacts valve tappet plunger to facilitate timing as pointer passes the Start Timing mark.
6. Work valve tappet plunger up and down until hydraulic valve tappet fills with fluid and all traces of air bubbles have disappeared.
7. Allow ram and weight to force hydraulic valve tappet plunger downward. Measure exact time it takes for pointer to travel from Start Timing to the Stop Timing marks of tester.
8. A satisfactory hydraulic valve tappet must have a Leakdown rate (time in seconds) within specified minimum and maximum limits.
9. If hydraulic valve tappet is not within specification, replace it with new hydraulic valve tappet. Do not disassemble and clean new hydraulic valve tappets before testing because oil contained in new hydraulic valve tappets is test fluid.
10. Remove fluid from cup and bleed fluid from hydraulic valve tappet by working plunger up and down. This step will aid in depressing tappet plungers when checking valve clearance (collapsed valve tappet gap).