BMW 3 Series 318i E30 Thermostat Engine Code -M40 B18 89-92

Thermostats & Thermostat Housings — OEM-Spec Temperature Control

Precise temperature control is the backbone of modern engines. This OEM-spec component (thermostat or integrated housing, depending on the application) restores correct warm-up behaviour, stabilises operating temperature, and protects against overheating in South African conditions.

Why replace the thermostat / housing

• Restores correct warm-up strategy and stable operating temperatures
• Prevents overheating, detonation and oil breakdown under SA heat
• Protects turbochargers, head gasket and emissions systems
• OEM-aligned design for fitment, sealing and sensor compatibility

Component overview

Common symptoms

• Temperature gauge drops at speed but climbs in traffic (stuck open)
• Overheating warnings, boiling sounds, or coolant push (stuck closed)
• Coolant residue or staining around housing joints and hose unions
• Heater weak at idle, improves with revs (air or poor flow)
• ECU codes for thermostat heater / temp correlation (electronic units)

What’s included

• Thermostat or thermostat-housing module matched to the listed application
• Seals/O-rings where applicable

Images are for illustration. Confirm by OE/part number, engine code and connector type. Contact us with your VIN for fitment support.

Installation best practice

• Flush system and refill with OEM-approved coolant and deionised water
• Clean mating faces; replace O-rings; torque fasteners to spec
• Follow the bleed procedure to remove air pockets (critical)
• For electronic units: check connector condition and route loom correctly

FAQs

Warranty & important notes

• 12-month warranty against manufacturing defects
• Warranty requires correct coolant, proper bleeding and torque procedures
• Mixing coolant types or using tap water may void warranty