scope:

Introduction

Note: Nothing in this standard supercedes applicable laws and regulations.

Note: In the event of conflict between the English and domestic language, the English language shall take precedence.

Note: The words must, shall, or will as used in this document means a mandatory requirement.

Note: In the event of conflicts between the content/intent of this document and a certified laboratory version, this and only this document shall take precedence. Discipline regarding this test and its execution will be maintained and enforced if necessary, with removal of certification if violations occur.

Note: Specifics as to what is considered a GMW3155 test, are listed in Appendix A, A4.

Note: No one involved in GMW3155 testing is to make judgments or interpretations as to content/intent of this document and take independent action as a result. Any and all procedural issues (including deviations) are to be immediately brought to the timely attention of the document sponsor and the GM Global Sealing Technical Specialist before the event is reached. Our intent is to drive continuous improvement of document content and not risk voiding a test, due to unauthorized deviations. Any tested procedural step or content conducted in a test (without one (1) time approval) and is not covered in the latest written version of GMW3155 [including Criteria for Thermal Cycling Test for Life Assessment of Powertrain Sealing Systems (GMW3155)], is prohibited.

Purpose.

This test is used to predict the life of powertrain sealing as it applies to the intended system design. The system includes the gasket, fasteners, structural interfaces, and circulating media.

This test is used on components and assemblies (up to entire engines and transmissions) to identify and eliminate marginal seal designs and/or materials. Design has a significant influence on test results. Production released or production intent parts shall be used.

Applicability.

This test is suited to the evaluation of all static powertrain gaskets and seals that experience thermal cycling during service. It is based on European and North American passenger vehicle and light duty truck applications. Other regional or vehicle applications, e.g., Heavy Duty (HD) trucks, may not experience the thermal cycle described in this standard.

This test permits the optional use of mechanical devices to impart motion or load on any test fixture(s).

High temperature applications (e.g., head, exhaust, turbo), or Exhaust Gas Recirculation (EGR) gaskets, are beyond the limits of this test.

Test Oils. The test fluid circulatory system (3.2.2) of each test unit shall permit steady and progressive oxidative degradation of the test oil to End of Test (EOT). Fluid degradation is measured using the appropriate fluid industry tests listed in 3.3.1.7. With no blow-by or Positive Crankcase Ventilation (PCV) recirculation provisions, this test does not replicate oil degradation under engine operating conditions.

Fluid Leak Requirements. All tested samples for validation have one (1) sealing performance requirement defined in a restricted General Motors Worldwide (GMW) document and supercedes all previous and existing statements. Any no leak criteria for evaluation during or after GMW3155, must be defined and/or have measurable values listed on the print, advance development and validation plan, and/or the Performance and Quality Management System (PQMS) test request.

High Pressure Fixture Integrity - Start of Test (SOT) and EOT. For high pressure coolant and oil joints (no spray) at SOT, apply the maximum fluid pressure as supplied by the component Design Responsible Engineer (DRE) or supplier. The default test time is 2 minutes. Repeat the high fluid pressure at EOT. No fluid leakage shall occur as defined by the latest written version of GMW3155 including Criteria for Thermal Cycling Test for Life Assessment of Powertrain Sealing Systems GMW3155.

Air Leak Requirements - Fluid Spray Joints Only. All tested samples for validation have media specific sealing performance requirements defined in a restricted GMW document and supercedes all previous and existing statements. Other no leak criteria for evaluation during or after GMW3155, must be defined and/or have measurable specified values listed on the print, advance development, and validation plan and/or the PQMS test request.

• For oil joints operating under atmospheric conditions, unless otherwise specified, the air leak default test condition is 2 minutes at 14 kPa (-0.3 kPa, +0 kPa) with no leak detected at SOT, each of the designated frequency intervals and at EOT.

Purpose of Air Leak Testing Fluid Spray Joints. Test fixture leak integrity at the specified test intervals is measured with air because fluid media spray patterns are not always 100% effective in properly distributing fluid to the evaluated joint. All evaluated fluid joints must pass air at the minimum default condition per 1.2.6 (no exceptions).

Test Fixture Limit Testing. Fixtures shall be at Least Material Condition (LMC) (3.3.4) at the lowest torque. Maximum material condition testing is optional. See 3.3.2.2.4.

Remarks. This standard describes the methods for evaluating sealing systems in their intended subsystem assembly using engine oil, transmission fluid, coolant, or air as a circulating medium. Test fixtures are cycled through hot and cold temperature extremes for approximately 12 weeks to 18 weeks continuously (24 h/day, 7 days/week). The performance measure is determined by test completion without unacceptable leakage (successful test).

Media Cycles. For each liquid testing medium, there is a thermal test cycle. Table 4 is for Engine Oil/Transmission Fluid. Table 5 is for Engine Coolant. Table 3 is for Air.

Before initially running, and at the end of the selected test procedure, the following tests are required:

• GMW3137 Dynamic Sealing Stress Measurement for Powertrain Sealing Systems. A method for measuring continuous stress distribution between the gasket and joint surfaces using an electronic sensor film. Films are capable to 200 °C continuous, permitting the sensor to be left in the joint during testing for select data capture at desired test intervals. This is optional if GMW3152 is used.

• GMW3149 Air Leak Testing for Leak Rate Determination of Powertrain Sealing Systems. This test establishes if the test fixtures and test joints have been sufficiently sealed prior to the SOT, and any leak path has been created at EOT.

• GMW3152 Static Sealing Pressure Measurement for Powertrain Sealing Systems. Commonly referred to as a Fuji Paper (www.fujifilmusa.com) test, it measures the initial contact sealing pressure distribution achieved in the test joint using contact pressure sensitive color developing film. Measurement during initial assembly confirms if the seal to joint contact is continuous and sufficient to survive the test. It may also be used as a diagnostic tool for leaking parts at EOT.

Fluid Exposure. Fluid exposure to evaluate hydraulic fluid joint sealing is by:

a. Spray bar only to cascade oil over the evaluated joints. All test fluid is effectively drained during noncirculation periods.

b. Spray bar and direct fluid contact as intended in the joint(s) under evaluation at pressure. A desired fluid level is maintained during non-circulation periods. The retained fluid in the fixture is agitated during circulation periods using an immersed agitation tube pumping the same test fluid.

c. Agitation bar only fully submersed in desired test fluid level.

d. Coolant joints are only evaluated by direct contact at pressure (no spray or agitation bar).

Requiring a supplier to have GMW3155 capability internally as a requirement for contact business is strictly prohibited. Logistically, it is impossible to certify all global sealing related suppliers. Candidate selection is carefully planned and controlled in part for testing consistency, business, and confidentiality reasons. Contract laboratories have declined to provide GMW3155 testing. We will continue to pursue contract services. Having internal GMW3155 capability is desired, however, General Motors Powertrain (GMPT) and all certified laboratories with contract services, maintain adequate test capability to evaluate sealing performance in a timely manner.