we changed the water pump it went bad and there is still a knock in it please help it is running really sluggish
Have your radiator checked, replace the radiator cap and thermostate, look at all your hoses and you should be just fine,, 2002M7
If it has a knock, you may have blown a head gasket, or worse, cracked the block.
engine was overheated and you may have damaged the head gasket or cylinder head. Cylinder compression test should be done to make sure that you did not blow the head gasket. Any trained mechanic should be able do this test for around $100.
STOP DRIVING THE CAR!!!! It is broken and you are making it way worse. Its like walking with a broken foot with no crutches for the car! Find a towing service immediately. What town do you live in? I can look for a european car repair shop for you. Greg is right, you probably blew the engine, so unless you have money for a new engine installed, I would let it go. If you have a 328i it will be like $5000 and it goes up from there.
I'm assuming you replaced the water pump due to an overheating problem (most water pumps fail due to leakage, so I'm assuming you drove the car with low coolant). If this is the case and you have an engine knock, you're in trouble. A knock signifies damage to the crankshaft/piston/connecting rod and the associated bearings. If it sounds like someone is hitting the engine with a hammer, you'll need to bring it in right away, before you do more damage. It's not going to be cheap (when is it with a BMW) and you may be better off selling the car and starting with a new car. Good luck. Greg
