Question about 1998 BMW M3
Heater core and radiator are separate issues. But, both may have the same problem. The best non-commercial way I have found to remove internal obstructions from either is to use a household calcium and rust remover (like CLR)...On heater cores, remove both hoses and fill the core with product, then let it stand for a couple of hours. then drain and backflush.
On engine radiator, remove it, plug the lower hose connection and do the same...fill with product, let stand then backflush, then turn radiator upside down & repeat in opposite direction. The reason standard water flush often does not work is that water simply goes around the plugged area and does not remove anything except for minor debris which sometimes can actually plug other passageways and make the condition worse.
Back to the heater. It's possible that a blend door is not operating and therefore not allowing hot air to enter the heater box...check this as well.
Definitely make sure that fan is coming on and that the thermostat is actually working (I don't trust anything new just because it's new) Also check sensor & relay for fan.
Likely information "overload" but I hope something here helps!
Posted on May 15, 2009
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Posted on Jan 02, 2017
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