Valve

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BACKGROUND
• RMEP was investigating L-Series engines failing hot test for performance issues and discovered tight
intake valve lash.
• After intake valve lash was corrected on the failed engines, no performance issues were noted in
subsequent test.
• Investigation into internal failures showed no concerns with valve lash set process so a head teardown
was conducted to deep dive related components and root cause. Found to be intake valve seats not
fully seated prior to machining.
• During same time-frame customers reported performance issues that were found to have this failure
mode on engines that had not failed in hot test.
FAULT CODE/FAIL MODE
• Intake valve seats were not pressed to bottom of seat pocket.
• Intake valve seats settled within the pocket during engine operation causing tight valve lash and
resulting in engine performance issues on a portion of the suspect population.
CURRENT STATE
• Root Cause Identified, suspect range identified, containment completed at RMEP (Engine Assembly &
Machining), campaign action initiated (engine head swap), and corrective actions implemented.
• Suspect Population : 56 Cylinder Heads in suspect range
• 20 heads built into engines
• 3 contained at RMEP
• 17 shipped to OEMs; Including 3 for Navistar
• 36 Loose Cylinder heads on CMES Hold for rework
Updated: 05/4/2022
COMPLETED
Step 3:
• Press depth limits tightened at seat press operation to detect observed
condition.
• Requesting the following engines be quarantined:
• EAP: 74935760 / Chassis: 487096
• EAP: 74938183 / Chassis: 635902
• San Antonio: 74932295 / Chassis: 333586
Step 6:
• Seat press ram mandrel detail reworked for clearance at the small
throat diameter.
NEXT STEPS
• Further review and refinement of press waveform monitoring
windows/limits.
• Complete internal rework and external head replacement.
• Evaluate read-across to other head machining lines within CMI.
ROOT CAUSE AND GOAL STATEMENT
• Root Cause: OP 110 seat press ram mandrel protruded through the seat and interferes with smaller
throat diameter (within spec on low limit) causing the seats to not be pressed completely to bottom of
seat pocket.
• Goal Statement: Implement processes to ensure valve seats are properly installed and more robust
internal detection.
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Op110 Valve Seat Press Pictures
Before
After
Intake Seat
(P/N 5300834)
Based on design, seat mandrel should only have chamfered end protrude, not full diameter, but
that was not the case on this tool. Due to full diameter protrusion, tolerance difference between
seat ID and cylinder head throat ID created interference.
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