The bmw 3 series e46 is quite a well built vehicle. It is much better in terms of build quality compared to equivelant year Mercedes C Class. The m43tu engine is a tried and test engine which has been around for around 10 years. The 318i e46 around 1999-01 with the m43tu was the car that out sold the Ford Mondeo. If you have this car then you may have come across an overheating problem.
Signs of overheating engine- temp light goes into the read. Drastic water loss. Steam from engine bay. Loss of power. Vehicle refusing to start.
1st thing to do before buying replacement engine is to check you radiator for any leaks. Then try K-seal. Fill radiator with water, let vehicle warm up, and loosen the bleed screw using a cloth an screwdriver, Be Careful. Steam will come out , this is the release of air from the cooling system. if this does not cure your overheating/waterloss then remove the thermostat housing, inspect the thermostat or replace complete, usually Eurocparts are the cheapest. If no joy, same problems, then you should inspect the water pump, make sure its circulating the water, it could be you have water in the cooling system but the pump is not working or is weak.
When you car is mid temp, just before going into the red, does the electric fan working? Some 318i models come with an electric cooling fan, if this not not come on, it may be the fan itself or the fan switch. inspect both item, you can put direct power to the fan to see if it works.
If your vehicle is still overheating, the you will require a replacement headgasket. Again eurocarparts are cheapest, also it should be noted the a cylinder head from the earlier e36 m43 will fit. usually a lot cheaper than buying a head for an e46.
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