I have bmw 735i v8 2000 only one of the four heater outlets blows hot air the rest blow cold also can hear water sound when i rev car but when heater is of their is no sound when i rev car

Did it blow hot air before you put water in it? Why did you put water in it? It's supposed to use a 50/50 coolant mixture.

Did you overheat the motor and it quit?

it appears that you have an air lock in the coolant system. bleed out the air by loosing of the highest hose until only water comes out or have the system pressure bled at a radiator shop.

These selections are run by Engine vacuum. sounds lie a diaphragm is NG to control the lower door

Replace the thermostat.

Have your thermostat checked, sound like it is not working when cold.

The heater operates from the hot water from the engine cooling system flowing through the heater radiator which is inside the air ducts under the dash. I suspect that the control wire/cable that goes from the heater control lever has broken or become disconnected from the heater tap that controls the volume of hot water through the heater radiator. Some times there is also a flap in the air ducts that is operated by the heater lever tha varies the amount of air that is heated. The tap may be in the engine bay or tucked in behind the air ducting.

check hot water is circulating through heater rad by feeling the inlet and outlet pipes as they come thru the bulkhead if ok it sounds like there is a control panel prob, if hot water isnt circulating make sure cooling system is bled properly, and you could try backflushing the system.

The Heater Control Valve has failed. It defaults to full defrost mode when it fails and blows hot air even when the A/C runs. Replacement part is $105 ...google Autohaus AZ for online parts ordering. BTW...HCV is located in the engine compartment right in front of the driver position in the corner by the firewall and inner fender...you'll see small coolant hose running to it.

Sounds like a thermostat sticking. Some things to do. First check coolant level is up and moving. Second (most likely), change thermostat. Very easy fix for backyard mechanic. Make sure to put thermostat in so water flow is correct direction. Look for arrow on side of thermostat. Next, is belt to water pump loose. Another easy fix in most cars.

motor is going bad replace it