also heater is not working properly
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1998 BMW 540i Question: what are the reasons for the cooling system to boil or fluctuating cooling temp
Answer #1csubak30 January 04, 2012, 23:47Master
Sounds like the thermostat is bad. Need to replace soon but make sure coolant is at proper level and not leaking. Other cause is heater core obstruction not allowing fluid to flow through properly. Hopefully, not the water pump.
British European Motors from BOSCH Service, January 09, 2012, 11:30Enthusiast
Thermostat problem, most likely.