Overview
ISO 4081:2016 specifies requirements for rubber hoses and tubing used in cooling systems for internal-combustion engines. It applies to straight or pre-formed hoses and tubing intended for pressurized or unpressurized cooling circuits containing 1,2-ethanediol‑based coolants (commonly ethylene glycol formulations) for vehicles with an unladen mass of 3.5 t or less. The standard also serves as a classification system that OEMs can use to define application-specific test call-outs (see Annex D).
Keywords: ISO 4081, rubber hoses, cooling systems, coolant hoses, automotive hose specification, OEM hose requirements.
Key Topics and Technical Requirements
- Classification: Four types by ambient temperature rating:
- Type 1: −40 °C to +100 °C
- Type 2: −40 °C to +125 °C
- Type 3: −40 °C to +150 °C
- Type 4: −40 °C to +175 °C
- Dimensional requirements: Bore sizes and tolerances follow ISO 1307; wall thickness must meet performance tests.
- Performance tests (selected as relevant per application):
- Burst pressure (ISO 1402) - specified minima for tubing and hoses by diameter.
- Adhesion between bonded layers (ISO 8033) - minimum values for unaged and aged samples.
- Low‑temperature flexibility (ISO 10619‑1/2 or SAE J20) - no cracking at −40 °C.
- Resistance to collapse (ISO 7233) - limits on diameter reduction under vacuum/temperature.
- Resistance to kinking, dilation, electrochemical degradation (SAE J1684), ozone (ISO 7326) and heat ageing (ISO 188).
- Compression set (SAE J1638) and resistance to engine‑oil contamination (Annex B).
- Pressure/vibration/temperature endurance (Annex C) with limits on burst pressure and dimensional change.
- Testing frequency: Type tests repeated at most every 5 years or after design/process changes; routine and production acceptance tests specified in Annexes E–G.
- Marking: Continuous marking required - manufacturer, ISO number (ISO 4081:2016), type and temperature limit, internal diameter (mm), manufacture date/quarter, and recycling code (ISO 1629).
Applications and Who Uses It
- Automotive OEMs specifying cooling system hoses for passenger cars and light commercial vehicles (≤3.5 t).
- Hose and tubing manufacturers, material suppliers, and contract moulders.
- Quality, R&D and test laboratories performing type and routine tests.
- Procurement and design engineers using the standard as a baseline for performance, marking and recyclability requirements.
Related Standards
Commonly referenced documents include ISO 1307, ISO 1402, ISO 10619‑1/2, ISO 188, ISO 1817, ISO 7326, ISO 8033, SAE J20 and SAE J1684 - useful for detailed test methods and material evaluations.
Use ISO 4081 when you need a recognized, test‑backed specification for automotive cooling hoses, consistent marking and traceability, and an OEM‑friendly framework for bespoke hose call‑outs.
Open preview (PDF)Rubber hoses and tubing for cooling systems for internal-combustion engines — Specification
