Radiator & Fan
A heat exchanger fighting for the engine’s life
Only about a third of fuel energy becomes motion — much of the rest is heat the engine must get rid of or destroy itself. Coolant carries that heat from the engine to the radiator, where hundreds of thin tubes and folded fins hand it to the passing air. The fan steps in when there isn’t enough airflow, like in traffic.
What it does
Transfers waste heat from the engine coolant to the surrounding air, keeping the engine near its ideal ~90 °C.
At the very front, behind the grille, in the path of incoming air.
How it works
- Hot coolant (~90–105 °C) from the engine enters the top of the radiator.
- It spreads through dozens of flat tubes; thin aluminum fins between the tubes multiply the surface area exposed to air by ~10×.
- Ram air at speed — or the electric fan at rest — carries the heat away; coolant exits the bottom 10–15 °C cooler.
- The pressure cap holds the system at ~1 bar over atmospheric, raising coolant’s boiling point to ~125 °C.
- A thermostat valve keeps coolant in the engine until it reaches operating temperature, then meters flow to the radiator.
Key numbers
| Core material | Aluminum tubes + fins, plastic tanks |
| Operating temp | 88 – 105 °C |
| System pressure | ~0.9 – 1.4 bar (cap rating) |
| Coolant | 50/50 antifreeze–water mix |
| Heat rejected | 20 – 60 kW under load |
Warning signs of trouble
- Temperature gauge climbing in traffic — failed fan or low coolant.
- Sweet smell or crusty pink/green residue — coolant leak.
- Overheating only at speed — clogged core or collapsed hose.
- Oil in coolant (milkshake) — failed gasket or internal cooler. Serious.
Maintenance & care
- Check coolant level at the expansion tank (cold) monthly.
- Replace coolant on schedule — old coolant turns corrosive.
- Never open the cap hot; the system is pressurized and will flash-boil.
- Gently clean bugs and debris from the fins.
Frequently asked questions
What does the radiator & fan do?
Transfers waste heat from the engine coolant to the surrounding air, keeping the engine near its ideal ~90 °C.
How does a radiator & fan work?
Only about a third of fuel energy becomes motion — much of the rest is heat the engine must get rid of or destroy itself. Coolant carries that heat from the engine to the radiator, where hundreds of thin tubes and folded fins hand it to the passing air. The fan steps in when there isn’t enough airflow, like in traffic.
What are the signs of a failing radiator & fan?
Temperature gauge climbing in traffic — failed fan or low coolant. Sweet smell or crusty pink/green residue — coolant leak. Overheating only at speed — clogged core or collapsed hose. Oil in coolant (milkshake) — failed gasket or internal cooler. Serious.
How do you maintain a radiator & fan?
Check coolant level at the expansion tank (cold) monthly. Replace coolant on schedule — old coolant turns corrosive. Never open the cap hot; the system is pressurized and will flash-boil. Gently clean bugs and debris from the fins.