2003 NISSAN SENTRA HEATER BLOWING AMBIENT AIR. JUST REPLACED THERMOSTAT AND HOSE AS IT WAS OVERHEATING, BUT NOT LEAKING. SERVICE ENGINE LIGHT JUST CAME ON LAST WEEK.

Good idea is to drain the coolant from your radiator, then replace the hose that is leaking and then fill with coolant to the proper level. Drive your car and have heater running to remove any air in the system.

remove both hoses from engine that passes through firewall to heater. put a stiff piece of wire in the hole and make sure it is clear. If there is no restriction, then the heater is choked up

Are you talking about the engine cooling system or a problem with your Auto A/C?

You have a leaking engine cylinder head gasket, this may be due to the previous overheat or a result of it, make sure when you have the engine repaired you find out if the cooling system is in good condition or the problem will recur.

Are you sure there is not a air pocket in the engine after changing water pump,
there is only 1 thermostat

you could have an air pocket in the cooling system that has to be burped. With a cold engine, park uphill and leave the radiator cap loose. Fill radiator and coolant reservoir. Start engine with cap loose and run at 1500 rpm until temp gauge reads normal. Feel if top radiator return hose from engine to radiator is hot. If yes, coolant is flowing and thermostat is open. If cold, thermostat is not staying closed until engine is hot.

report results.

i have a 2005 1.8 nissan sentra.i rplaced the radiator becuause it was leaking.so when i did i took it for a test drive and the needle went to hot then back down to middle ways between the C & H BACK IN FORTH.so i replaced the thermostat. now as far as i can tell it is staying in the middle of C & H. i can't feel no water though cerulating through the top or bottom hose of the radiator. so now that i told you what i done so far my question is???? ( my heater is not working in the car it is blowing out cold air & i left the car runnng for about 45 min. even took it up and down the road.still cold air.what do you think i need to do?????????? )

My 2005 Nissan Sentra 1.8s with 55,000 mi. blows cold air from the heater. Coolant not circulating in engine. Lower hose stays cool to touch. Both heater hoses cold. Changed thermostat - didn't fix it. Coolant not leaking or dirty. None in oil - no oil in radiator. Changed worn water pump belt - pump spins freely with no noise or resistance. Cooling fans come on after warm-up. Temperature gauge stays in normal range then jumps to hot and back again. Coolant good to 10 below - didn't freeze here yet. No other problems or repairs to car. Afraid to drive and make worse. Help!

My 05 sentra with 79k miles heat will warm up and then get cold after a mile of driving, we have tried to get the air pocket out, the mechanic stated he thought it could be a blown head gasket, another mechanic said it was a bad heater core. Any advice would be appreciated.

does the car overheat at idle or travelling down the road? if the thermostat was not changed, thats first step. checking it is replacing it. possibly air-bound. then i would suspect a headgasket problem.