Radiator Caps and Coolant Hoses by Component Type
Imara Engineering's caps and hoses catalogue covers every pressure and flow component in your machine's coolant circuit. This page is part of our Radiators and Coolers family. If your machine also requires a radiator, engine oil cooler, or cooling fan alongside your caps and hoses, our team can source and confirm all components together in a single order. Browse by component type below or contact us with your machine serial number for an immediate part match.
Radiator Caps and Pressure Caps
The radiator cap is a precision pressure valve, not a simple cover. It holds the cooling system at a specific operating pressure determined by the engine manufacturer to ensure coolant remains liquid at operating temperature. It also allows controlled coolant expansion into the overflow tank and reseals the system as it cools, maintaining a closed circuit that prevents air ingestion and coolant contamination. A radiator cap that has lost its pressure rating or its sealing integrity compromises the entire cooling circuit it is supposed to be protecting.
Imara Engineering stocks radiator caps and pressure caps for the following platforms:
- Cat radiator cap — confirmed fitment across CAT excavator, dozer, and wheel loader platforms
- Caterpillar radiator cap variants, including the 6l8617 radiator cap OEM cross-reference
- Cat c15 acert radiator cap psi — rated to OEM pressure specification for the C15 ACERT engine cooling system
- Komatsu radiator cap — fitments for PC200, PC300, D65, and D85 machine platforms
- Hitachi radiator cap units for ZX-series excavator platforms
- Radiator cap pressure heavy equipment variants cross-referenced by machine model and OEM part number
Upper and Lower Radiator Hoses
The upper and lower radiator hoses are the primary coolant transfer conduits between the engine and the radiator, carrying hot coolant from the engine outlet to the radiator inlet and returning cooled coolant from the radiator back to the engine. These hoses operate under constant pressure cycling, sustained elevated temperatures, and continuous vibration from the engine and undercarriage, all of which degrade the hose material from the inside and outside simultaneously over time.
Imara Engineering stocks the following radiator hose units:
- Upper radiator hose excavator units for CAT, Komatsu, and Hitachi platforms
- Lower radiator hose excavator units, cross-referenced by machine model and serial number
- Radiator hose excavator assemblies with OEM-matched internal diameter and wall thickness
- Hose kits covering both upper and lower positions for complete coolant hose replacement in a single service
Bypass Hoses
The bypass hose routes coolant from the engine back to the water pump when the thermostat is closed and the engine is warming up, maintaining coolant circulation through the engine block before the radiator circuit opens. A failed bypass hose excavator unit disrupts this warmup circulation, creates localised hot spots in the engine block during cold start conditions, and in severe cases causes thermostat housing seal failure from the pressure spike that occurs when coolant has no bypass path. Imara Engineering stocks bypass hose excavator units for CAT, Komatsu, and Hitachi machines, cross-referenced by machine model for confirmed fitment.
Coolant Overflow Tanks
The coolant overflow tank excavator assembly is the reservoir that receives expanding coolant from the cooling system as engine temperature rises and returns it to the circuit as the engine cools, maintaining a closed system that prevents air from entering the coolant circuit through the radiator cap seal. A cracked or failed overflow tank allows the system to expel coolant that is never recovered on cool-down, causing a progressive coolant level reduction that is easy to miss in daily checks until the system is running significantly low. Imara Engineering stocks coolant overflow tank excavator units for the major CAT, Komatsu, and Hitachi excavator platforms with OEM-matched capacity and connection geometry.
Radiator Caps and Coolant Hoses by Machine Platform
Imara Engineering's caps and hoses range covers the major machine brands operating across global construction, mining, and infrastructure sites. Contact our team with your machine serial number for direct part identification across any platform.
Caterpillar Radiator Caps and Coolant Hoses
Caterpillar machines operate across the widest range of heavy equipment applications in the global market, and their cooling system pressure and hose specifications vary significantly across engine families, machine sizes, and build years. Our caterpillar radiator cap and coolant hose excavator range is cross-referenced against CAT's full machine and engine serial number database to ensure every part supplied matches the correct pressure rating and connection geometry for the specific machine it is serving.
Compatible CAT platforms include:
- CAT 302.5, 308, 315, 320, 323, 330, and 336 series excavators
- CAT D6, D7, and D8 dozer radiator cap and coolant hose fitments
- CAT 930, 938, and 950 wheel loader caps and hoses
- Cat C15 ACERT radiator cap psi-rated units for the C15 ACERT engine family
- 6l8617 radiator cap OEM cross-reference for confirmed CAT fitment
- Additional CAT platforms available — contact our team with your serial number
Komatsu Radiator Caps and Coolant Hoses
Komatsu excavators and dozers are among the most widely operated machines on construction and mining sites globally, and their cooling system pressure cap and hose specifications are matched precisely to the thermal demands of each engine platform. Our Komatsu radiator cap and coolant hose range covers the primary Komatsu excavator and dozer platforms operating across Australia, Southeast Asia, Africa, and the Americas.
Compatible Komatsu platforms include:
- Komatsu PC130, PC200-8, PC290, PC300, and PC400 series excavators
- Komatsu D65, D85, and D155 dozer radiator cap and coolant hose fitments
- Komatsu WA380 and WA470 wheel loader caps and hose kits
- Coolant overflow tank excavator units for Komatsu PC-series platforms
- Additional Komatsu platforms available — contact our team with your machine serial number
Hitachi Radiator Caps and Coolant Hoses
Hitachi ZX-series excavators are extensively deployed across construction and civil works projects in high-ambient-temperature environments where cooling system integrity is critical to machine availability. Our Hitachi radiator cap and coolant hose excavator range covers the primary ZX-series platforms, with upper and lower radiator hose units, bypass hose assemblies, and pressure caps available for confirmed fitment.
Compatible Hitachi platforms include:
- Hitachi ZX130, ZX200, ZX225, ZX270, and ZX300 series excavators
- Hitachi ZX350, ZX450, and ZX490 large excavator caps and hose fitments
- Hitachi EX-series coolant hose excavator units for older fleet machines
- Additional Hitachi platforms available — contact our team with your machine serial number
Why Radiator Caps and Coolant Hoses Fail and What to Watch For
Caps and hose failures share a common characteristic: they give early warning signs that are easy to dismiss as minor issues until the failure becomes a full cooling system emergency on site.
The Most Common Failure Causes
- Pressure cap spring fatigue from repeated thermal cycling, compressing and releasing the internal spring mechanism, progressively reduces the cap's holding pressure below the system's rated operating threshold, allowing coolant to escape under operating conditions before the engine reaches critical temperature
- Cap seal deterioration from ozone exposure, heat aging, and coolant chemical attack hardens and cracks the rubber sealing ring, causing the cap to leak pressure at the sealing face without any obvious visual sign of failure until the coolant level is checked
- The inner wall hardens from heat aging, causing the internal surface of the hose to crack longitudinally, restricting coolant flow without any visible external sign until the hose collapses fully under operating vacuum on cool-down
- Hose external swelling and softening from oil contamination on the outer hose surface, degrading the rubber compound and causing the hose to balloon under operating pressure before rupturing
- Bypass hose collapse during cold start from a hose that has lost its internal structural integrity and is no longer resisting the vacuum created by the water pump during the engine warmup cycle
- Overflow tank cracking from ultraviolet degradation and repeated thermal expansion cycles, creating hairline cracks in the tank body that cause slow coolant loss without any obvious visible pooling under the machine
Inspection Steps to Catch Failures Before They Become Emergencies
- Check the coolant level in the overflow tank at every daily pre-start inspection and investigate any unexplained level reduction immediately, rather than simply topping up
- Inspect the radiator cap sealing ring visually at every major service interval for hardening, cracking, or deformation, and replace the cap if any of these signs are present, regardless of whether the system is losing coolant
- Squeeze all accessible coolant hoses by hand during cold inspections — a hose that feels hard, brittle, or has surface cracking is at the end of its service life and must be replaced before it fails in operation
- Check hose connection clamps for corrosion and correct torque at every service interval — a hose that is in good condition but held by a corroded or undertightened clamp will leak at the connection point under operating pressure
- Inspect the overflow tank body and neck for hairline cracking during every major service and replace the tank if any cracking is visible — a cracked tank cannot maintain the closed-circuit pressure recovery the system depends on
Why Small Parts Carry the Biggest Risk in Your Cooling System
The True Cost of Ignoring a Radiator Cap or Coolant Hose
A radiator cap costs a fraction of what any other component in your machine's cooling system costs. A coolant hose replacement is a scheduled maintenance item with a known service life. Neither is a significant procurement event. What is significant is what happens when either is allowed to fail in service on a working machine. Coolant loss from a failed cap or ruptured hose causes engine temperature to exceed safe limits within minutes under working load. The engine's thermal protection systems will attempt to manage the event, but are designed to prevent catastrophic failure, not to substitute for coolant. The resulting damage to head gaskets, cylinder head sealing surfaces, and in severe cases cylinder liners and pistons turns a minor maintenance item into a major engine repair that removes the machine from service for days or weeks. Imara Engineering stocks radiator caps and coolant hoses precisely because the cost of stocking the right cap and hose for your machine is negligible compared to the cost of the alternative.
OEM Pressure Rating Is Not Interchangeable
Every machine's cooling system is designed to operate at a specific pressure rating determined by the engine manufacturer and reflected in the radiator cap pressure heavy equipment specification for that platform. Installing a cap with a lower pressure rating than specified allows the coolant to reach the boiling point at lower temperatures than the system was designed to tolerate, creating coolant loss and localised overheating under conditions where the engine would otherwise operate normally. Installing a cap with a higher pressure rating than specified places excessive stress on hose connections, the radiator tank seams, and the overflow system. Imara Engineering supplies caps rated to the correct OEM pressure specification for each machine platform. Fitment and pressure rating are both confirmed before every order is processed.
Part of the Complete Radiators and Coolers System at Imara Engineering
Radiator caps and coolant hoses are the connective elements of a cooling system that also depends on a functional radiator, oil coolers, an intercooler, and cooling fans to operate correctly. A machine that has experienced a hose failure or coolant loss event should also have its radiator, thermostat, and pressure system inspected before returning to service to confirm no secondary damage has occurred. Imara Engineering stocks the complete Radiators and Coolers range across all of these components. If your machine requires a full cooling system inspection and multiple component replacements, contact our team, and we will source and confirm everything together in a single order.
