I have a 2001 Nissan Sentra, just picked it up last week. I have flushed the cooling system several times, even the heater core seperately. I have checked the thermostat. Engine runs great, no coolant in the oil, not leaking anywhere. Sometimes I have cabin heat but most of the time I don't, yet the engine is up to temp. Sometimes the engine does get hot but then cools off itself, still no cabin heat.

 

Yes i will post this again and it's my article i wrote. Check all the following. www.enginemisfire.com


Check #1 Is there enough coolant? Locate coolant reservoir. Coolant should be even with full marking on reservoir. If coolant is low, find out if there is a leak. Leaks can occur due to hoses harden, cracks, breaks, chafed, burned, oil soaked or swollen. Observe heater core hoses, radiator upper hose and lower radiator hose for possible problem.

Check #2 Heater core can rust and develop leaks allowing coolant to drip on the car’s floor. Locate heater core and observe area inside the passenger floorboard.
Check #3 Observe around the thermostat housing for possible leaks

Check #4 Observe leaks around radiator cap
Check #5 Observe around the water pump area by the vehicle’s timing belt. Are there signs of coolant leak and drips?

Check #6 Sign of Bad thermostat- Thermostat stuck open and Temperature gauge always low.
Thermostat function: A thermostat operation is to remain closed to allow coolant circulates around inside the engine block, cylinder head, and intake manifold until the engine is warm. A stuck open thermostat will not allow engine to reach operating temperature therefore resulting cooler coolant temperature.
Check #7 Heater control valve malfunction. Heater control valve should move when heater is turned on. Heater Control Valve can move manually by hand and is located by fire wall.
Check #8 Clogged heater core. There are two hoses running through the firewall. Check both hoses. If one hose is warm and the other hose is cold. It is a sign of a clogged heater core.

Heater core function: A heater core is a small, radiator-like unit that provides a large surface area for heat dissipation into passenger compartment. It is made of a series of tubes surrounded by finds. As air passes through the tubes and finds, heat is transferred by air.
Check #9 Blower motor malfunctions. Observe the blower motor connection. Is the connection secured?
Blower motor function: A motor that force air through the heater core.
Check #10 Observe exhaust tail pipe. Is your vehicle smoking white? A sign of white smoke is blown head gasket. A blown head gasket allows coolant in the chamber to burn.

 

OK there is no problem with my car. Grrrrr. I have checked everything even removed the waterpump last night only to find that it looks great. Flushed the rad and heater core again, ran water through the block, no obstructions. Filled the rad with coolant until it came out the bleeder hole, disconnected the heater core hoses and ran the engine until it was hot enough to open the thermostat and still no water was pumping out the hoses to the heater core. OMG, this thing is ticking me off. LOL
Is there a special trick to getting all the air out of this system? It seems like an air lock but I cannot get rid of it.
"Help"

 

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