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.

Purpose/Material Description.

This specification covers hydrogenated nitrile rubber (HNBR) used in static sealing against extended life coolant for gas and diesel engines.

Note: The words must, shall or will as used in this document mean a mandatory requirement. Commercial compounds are divided into the following types:

Type A.

All 25% to 36% acrylonitrile (ACN) HNBR gasket or O-ring compound(s) in contact with engine coolant for application temperatures with a functional temperature range of -29 °C to 125 °C (continuous) as defined by ASTM D1329 TR10 and SAE J2236 respectively.

Type B.

All 36% to 44% acrylonitrile (ACN) HNBR gasket or O-ring compound(s) with a functional temperature range of -18 °C to 135 °C (continuous) as defined by ASTM D1329 TR10 and SAE J2236 respectively.

Symbols.

Identify the elastomer nomenclature using ASTM D1418 or ISO 1629.

Applicability.

This standard covers the use of hydrogenated nitrile elastomer whose function is to seal cooling system components (e.g., water pump, oil cooler or front engine cover, etc.) Type A is used for general use. Type B covers higher coolant operating temperatures (e.g., turbo).

Other Coolant Standards.

Use GMW14747 for coolant joints not exposed to hydraulic fluids during initial assembly or service. Use GMW14751 for joints sealing oil and coolant simultaneously. Use GMW17470 as a lower cost alternative to GMW14751 for coolant joints with incidental exposure to hydraulic fluids during assembly or service.

Remarks.

The acrylonitrile (ACN) content of HNBR influences the low temperature of the compound. High ACN (35% to 43%) sacrifices low temperature flexibility. Low ACN content (18% to 23%) of HNBR improves low temperature flexibility.

O-rings.

Some prints/drawings identify “D” or racetrack shapes as O-rings. To avoid confusion, testing and table data only apply to the ASTM D1414 definition of an O-ring.

Tensile and elongation properties of O-rings are measured by spool separation, however, during this step, the elongation across the specimen width is not uniform. To minimize data variation, the recommended ratio of ring inside diameter (ID) to cross section width should be 9 to 1 or greater. Of greater interest is tensile stress at 20% to 50% elongation because it is closer to the performance range of the O-ring.

Note: The ratio for SAE AS568-214 size is 7 to 1.

Compression Set.

Testing a whole O-ring for compression set is not permitted. Air trapped in the O-ring inside diameter results in a different thermal condition between the inside and outside surface of the specimen.

Elastomers used in part of assembly (POA) are usually selected by supplier-specific criteria and often remain unspecified or unidentified on end user prints and drawings. As the original equipment manufacturer (OEM) end user, GM reserves the right (through directed buy) to define common rather than source-specific requirements. Use this document in the appropriate Statement of Requirements, Appendix C, and corporate prints and drawings using Section 8 Coding.

Compression Stress Relaxation.

Per GMW17113, deflection is 15% for manual and continuous. Note that only one method, manual or continuous, must be run. Only one method is required not both methods. For manual, there is the option of running 35% deflection in addition to the required 15%. 15% deflection replicates least material conditions (LMC) and 35% replicates most material conditions (MMC).