A clean, correctly filled cooling system is essential for engine life. Regular coolant servicing helps prevent overheating, corrosion, scale, water-pump damage, liner cavitation and freezing.
Never remove a radiator or pressure cap from a hot engine. Pressurised coolant can erupt as steam and boiling liquid. Allow the engine to cool fully before opening the system.
Why Coolant Maintenance Matters
Coolant does more than prevent freezing. The correct mixture also helps:
- Prevent internal corrosion
- Raise boiling protection
- Lubricate water-pump seals
- Reduce scale formation
- Protect wet cylinder liners where applicable
- Control cavitation
1. Identify the Correct Coolant
Use the operator or workshop manual to confirm:
- Coolant type
- Antifreeze specification
- Mixture ratio
- Cooling-system capacity
- Change interval
Do not choose coolant purely by colour. Different coolant chemistries may use similar colours.
Mixing incompatible coolant chemistries can reduce corrosion protection or form deposits. If the existing coolant type is unknown, a proper drain and refill may be safer than topping up with a guessed product.
2. Check Coolant Level
Check only when the engine is cold unless the manufacturer specifies otherwise.
Inspect
- Radiator level
- Expansion tank level
- Hoses and clamps
- Water pump
- Radiator seams
- Heater hoses where fitted
If coolant level keeps falling, find the leak instead of repeatedly topping up.
3. Check Coolant Condition
Coolant should be reasonably clean and free from oil, rust and sludge.
Warning Signs
- Brown or rusty coolant
- Oil floating on coolant
- Heavy sediment
- Milky contamination
- Strong fuel or exhaust smell
4. Check Antifreeze Strength
Use a suitable hydrometer or refractometer if required.
Too little antifreeze can reduce freezing and corrosion protection. Too much concentrate can also reduce cooling efficiency and may not give better protection.
5. Clean the Radiator Externally
A radiator can be full of good coolant and still overheat if airflow is blocked.
Remove
- Grass seed
- Chaff
- Dust
- Mud
- Oil-soaked debris
Also clean any oil cooler or air-conditioning condenser mounted in front of the radiator.
Use compressed air or low-pressure water carefully. Excessive pressure can fold radiator fins over.
6. Inspect Hoses
Check upper and lower radiator hoses and smaller bypass/heater hoses.
Replace hoses that are
- Cracked
- Bulging
- Oil soaked
- Very hard or brittle
- Soft and collapsing
A lower radiator hose can sometimes collapse internally under engine speed and restrict coolant flow.
7. Check Hose Clamps
Loose clamps cause leaks and can allow air into the cooling system.
Do not overtighten clamps to the point of damaging the hose neck or radiator fitting.
8. Inspect the Fan Belt
If the belt drives the water pump or cooling fan, check:
- Tension
- Cracks
- Glazing
- Oil contamination
- Pulley alignment
9. Check the Fan and Shroud
- Fan blades intact
- Fan fitted correctly
- Shroud secure
- Viscous coupling working where fitted
- Electric fan operating where fitted
A missing or damaged fan shroud can greatly reduce airflow through the radiator.
10. Drain the Cooling System
Only drain when the engine is cool.
- Place a suitable container beneath the drain.
- Remove the radiator/expansion cap when safe.
- Open radiator drain if fitted.
- Open engine block drain if specified.
- Allow the system to drain completely.
Some engines retain a surprising amount of coolant in the block unless the block drain is opened.
11. Flushing the System
If coolant is rusty or dirty, flushing may be necessary.
Possible Methods
- Clean-water flush
- Manufacturer-approved cooling-system cleaner
- Professional radiator cleaning
Avoid aggressive chemicals not approved for the engine, especially on aluminium components.
12. Thermostat Inspection
A thermostat is a serviceable cooling-system component, but it should not be removed permanently as a routine fix.
Check if:
- Engine warms too slowly
- Engine overheats rapidly
- Coolant circulation appears abnormal
- Thermostat has been removed previously
Use the correct opening-temperature thermostat for the engine.
13. Water-Pump Inspection
Check for:
- Coolant leakage
- Bearing noise
- Shaft play
- Damaged pulley
- Wobble
Leakage from a pump vent hole usually indicates seal failure.
14. Radiator / Pressure Cap
The cap controls system pressure and coolant recovery.
Inspect
- Rubber seal
- Spring condition
- Cap seating surface
- Correct pressure rating
Do not fit a higher-pressure cap to try to stop coolant loss.
15. Refill the Cooling System
- Close all drains.
- Mix coolant correctly if not using premix.
- Fill slowly.
- Open bleed points if fitted.
- Fill expansion tank to correct level.
- Start engine and warm gradually.
- Check for leaks.
- Allow engine to cool and recheck level.
16. Avoid Airlocks
Air trapped in the cooling system can prevent circulation and cause local overheating.
Airlocks are more likely after
- Thermostat replacement
- Water-pump replacement
- Radiator replacement
- Engine rebuild
- Complete coolant drain
Use the manufacturer bleeding procedure where provided.
17. Wet-Liner Diesel Engines
Some heavy-duty diesel engines use wet cylinder liners and require coolant chemistry that protects against liner cavitation.
Depending on the engine, this may involve:
- Supplemental coolant additives
- Specific extended-life coolant
- Regular coolant-condition testing
Do not substitute plain water for long-term use.
18. Coolant Service Intervals
Coolant additives wear out even if the fluid still looks clean.
Follow the specified:
- Calendar interval
- Engine-hour interval
- Coolant test interval
19. Long-Term Storage
A machine stored over winter should still have correct antifreeze protection.
Before storage:
- Check coolant strength
- Repair leaks
- Clean radiator
- Check hoses
20. Used Coolant Disposal
Used coolant can be harmful to people, animals and the environment. Store it in a clearly marked container and take it to an authorised recycling or waste facility.
Some antifreeze has a sweet taste but can be highly toxic. Clean spills promptly and store waste coolant securely.
Cooling System Service Checklist
| Item | Check |
|---|---|
| Coolant type | Correct specification and chemistry. |
| Mixture strength | Correct freeze/corrosion protection. |
| Coolant level | Correct when cold. |
| Radiator | Clean externally and no leaks. |
| Hoses | No cracks, bulges or collapse. |
| Fan belt | Correct tension and condition. |
| Water pump | No leakage, noise or shaft play. |
| Pressure cap | Correct rating and sound seal. |
| Final check | No airlocks, leaks or abnormal temperature. |
Related Agrimanual Manuals
Coolant capacities, thermostat temperatures, antifreeze specifications and bleeding procedures vary by engine and machine.
- Search Agrimanual for cooling-system service information
- Search Agrimanual engine workshop manuals
- Request a manual if your machine is not listed
Frequently Asked Questions
Can I use plain water instead of coolant?
Only as a temporary emergency measure where freezing is not a risk. Correct coolant provides corrosion, boiling and cavitation protection that plain water does not.
Can I mix different coloured antifreeze?
Colour does not reliably identify coolant chemistry. Mix only when compatibility is confirmed.
Why does coolant level drop after a coolant change?
Air may have worked out of the system and filled previously empty passages. Recheck when fully cold and inspect for leaks.
Should I remove the thermostat to improve cooling?
No, not as a routine fix. Many engines rely on the thermostat for correct flow control and bypass operation.
How often should coolant be changed?
Follow the machine’s service schedule. Conventional and extended-life coolants can have very different change intervals.
Cooling-system maintenance is cheaper than repairing an overheated engine. Keep the radiator clean, the coolant correct and leaks repaired.