Rm200 hot in the back but doesnt cool inside

get ur car hot, then hop out and check the cooling fan to make sure its spinning and pushing air to the engine, also heck your coolant levels

get test tool called a block tester (a free loner tool from Autozone) the test fluid for tester is about $8.00 us open hood on your car make sure fluid in coolent resivour is about 3 inches low so u dont get coolent in tester. run car at high speed till it is hot be careful opening resivovr that u dont burn yourself. put blue fluid in tester,put tester in resivour sealing it as best as possible squeeze bulb for up to 2 minutes sucking only air. if fluid turnes yellow you have a head gasket leek. they dont always blow white smoke.but may if you drive them long enough. if this is helpful please leave me great feed back.

Check for correct voltage ,also would check capacitor and motor rotation.

Check to make sure both hoses are getting hot. A significant amount of temperature differential could indicate a bad or incorrectly installed thermostat, air in the system or a plugged radiator. I would also put a block tester especially if it overheated badly as it could have blown the head gasket. The block tester will indicate if exhaust gasses have found their way into the cooling system by way of a blown head gasket which may cause vehicle to overheat.

An explanation of the cooling system.
You start your car, it is cold at first. The thermostat is shut. Car warms up and raises the temperature of the coolant in the engine block. Thermostat opens up. Water from the radiator (cool) is exchanged for water from the engine block (hot) The cool water causes the thermostat to shut. This traps the hot water in the radiator so that it can be cooled down. The cool water that was exchanged for the hot water, now becomes the hot water because it is in the engine block. It heats up until it's temperature causes the thermostat to open again, exchanging cool water for hot water. If you have no thermostat, then you will never hold water inside your radiator. You have to hold it there to allow it to cool off, then it becomes useful to cool your engine. So, yes put a thermostat back in it, and please vote as to whether this was helpful or not.

you didn't say that you replaced the thermostat....sounds as if it is sticking. You can always remove it and put the housing and such back together (w/o the thermostat), you won't have heat; but this will tell you if the thermostat is the problem or not. Also there is a temp sending unit....usually around the thermostat housing - indicated with a elec. plug running to it. It would be a good idea to remove it from the housing and clean/replace it, the sending unit can also make the engine run terribly if not working properly, and decrease gas mileage significantly.

Most likely your thermostat has failed and is stuck open. Engine coolant goes through the heater core and is used to heat the air that is blown into the cabin. If the thermostat fails, the coolant doesn't stay inside the engine long enough to absorb enough heat to make the climate control air blow hot. Change your thermostat (flush the coolant and have it replaced while you do this), and you should be back in business.

You need a complete cooling system check-up