BMW Cooling System Refresh — The Complete Parts List

Why a Full Refresh?

BMW cooling systems use plastic components that become brittle with age and heat cycling. Rather than replacing parts one at a time as they fail (risking overheating and engine damage), experienced BMW owners replace the entire system at once.

E46 Cooling System Refresh

Part	Brand	Approx Cost
Expansion tank + cap	Mahle/Behr	€40-60
Thermostat (88°C)	Wahler	€30-50
Water pump	Graf/Saleri	€50-80
Upper radiator hose	Rein	€20-30
Lower radiator hose	Rein	€20-30
Radiator (if >150k km)	Behr/Nissens	€100-200
Coolant temp sensor	FAE	€10-20
Hose clamps (spring type)	OEM	€15-25
BMW coolant (HT-12)	BMW	€20-30
Total		€300-500

E90 / F30 Cooling System Refresh

Part	Brand	Approx Cost
Electric water pump	Pierburg	€200-350
Thermostat	Wahler/Mahle	€80-120
Expansion tank + cap	Mahle	€40-60
Coolant hoses (set)	Rein	€60-100
Coolant temp sensor	FAE	€10-20
BMW coolant (HT-12)	BMW	€20-30
Total		€400-700

Coolant Types

• BMW HT-12 (blue/green) — current specification
• BMW LC-18 — older specification, compatible
• Mix ratio: 50/50 with distilled water
• Never mix different coolant types
• Never use tap water (minerals cause deposits)

Bleeding Procedure

BMW cooling systems are notoriously difficult to bleed due to the electric water pump:

1. Fill system with coolant
2. Start engine, set heater to max
3. Use ISTA/diagnostic tool to run the bleed procedure (activates water pump at various speeds)
4. Monitor coolant level in expansion tank
5. Top up as air is purged
6. The process can take 15-30 minutes

Without diagnostic tool: Run engine at idle with expansion tank cap off, squeeze upper hose periodically to help air escape. Less effective but workable.