i was having overheating problem with my 01 max i put new thermostat and WCV , fan and radiator and it was still overheating so i went and took out the thermostat and the water control valve from the car and now the car is running fine with out overheating... Is there any problem running the car with no thermostat and water control valve ???

 

You have have started 3 different threads about the same overheating issue you are having:
(http://forums.maxima.org/5th-generat...ure-level.html)
(http://forums.maxima.org/5th-generat...erheating.html)
I think it would be much better if you stick to one of them and keep reporting back until the issue is resolved. That way, people who are trying to help with your problem can see the history of the whole thing and you avoid having the same questions asked over and over again.
To answer your question, running your car without those two can lead to other issues; there's a reason why cars have those. I don't know how long you drove your car to determine that "is running fine", but it could be that now will take longer to overheat.

 

Shot in the dark: air in the system, water pump and/or coolant temperature sensor.

Not many other cooling system components remain.

 

The water control valve only effects the heater core. It allows your climate control to operate correctly and has nothing to do with engine cooling.

The thermostat brings your engine up to operating temp and regulates it. 180-190 F.
Operating without it will cause slow warm up time and possibly cold engine temps in colder weather. That will cause your engine to run rich, wasting fuel and possibly damaging your cat.

Was the thermostat installed the correct way?
Did you purge the air out of the system?
Have you had the system pressure tested?
Are you loosing coolant?

 

I think the water control valve does more than you think:

 

The coolant control valve does not allow coolant flow through the block until the coolant control valve starts to open at 203 F (fully open at 216 F). It has nothing to do with the heater (heater coolant flow control valves have gone the way of the Dodo). In other words, coolant flows out of the heads ONLY to the rad when the thermostat starts to open at 180 F (coolant is always flowing through the heater core) per the schematic. Reinstall the thermostat (brass bleeder "twitcher" must be up), and the coolant control valve ASAP. Getting the full coolant capacity amount into the system isn't always easy and requires a couple of topups after running the engine and bleeding the air out of the system (ensure that no air is coming out of the bleeder screw). The Gen. 5.5 cars do NOT have the coolant control valve or the bleeder screw. Coolant is therefore flowing through the block and heads to the rad when the thermostat starts to open.