2001 nissan sentra overheating replace the radiator, both hoses, thermostat and water pump. both fans work and come on at running temp. no smoke and oil is not cloudy. any ideas

Faulty thermostat is the most likely one.
Failed Radiator Fan / Sensor (equally likely)
Low coolant level (in radiator as opposed to reservoir)

Faulty water pump. (less likely)

Clogged radiator. (less likely)

Very weak mixture. (even less likely)

While there are a variety of reasons your Nissan Altima is overheating, the most common 3 are a coolant leak (water pump, radiator, hose etc.), the radiator fan, or a failed thermostat.

Nissan Altima Overheating - RepairPal

1. The radiator cap if working correctly it will release pressure in the system provided the cap you have is the correct pressure setting. If you are having a problem with pressure then replace the cap with a new radiator cap with the correct pressure setting. Do not use a cap with a pressure setting other than the original equipment pressure spec. So you do not go to the parts store and buy any radiator cap on the shelf that fits because they come with different pressure ratings and some of these will be totally unsuitable for your car.

2. If the pressure valve is stuck in the "old" cap the pressure release system will not work.

3. Overheating
Air pockets in the cooling system can definitely cause overheating and can retard coolant flow through the system. If you are draining the radiator to replace the coolant or replacing the radiator you need to follow the correct procedures for bleeding air out of the system for that particular engine after coolant refilling. Some engines have bleeder screws on the cooling system to assist in the air bleeding procedure and some don't.

There are various causes for overheating so don't assume it will necessarily be solved by bleeding any remaining air from the cooling system and replacing the radiator cap with one that works.

Other causes can be...........
1. Faulty cooling system thermostat. (Replace the Thermostat)
2. Faulty water pump, especially if the impellers have corroded away or have disintegrated in the case of those design genius water pumps with plastic impellers. (Replace the water pump)

3. Cooling fans not working and if so the cause needs to be tracked. Check that your fans are kicking in. If the engine is overheating the fans should be running because they will switch on when the coolant reaches a specific temp and well before the coolant gets excessively hot.

4. A partial blockage in the coolant passages inside the engine but not in the radiator if you have a new one. If the coolant is not changed at the required intervals(frequently the case with many owners) or is over diluted with water you can get a build up of debris. If products like stop leak have been used in the system this can create similar problems with partial blockages inside the engine coolant passages.

5. A compression leak into the cooling system.
If you have bled air from the system and have continuous air bubbles in the cooling system I would suspect a compression leak. In that event a basic leak down test will show if you have compression gasses leaking into the cooling system and from which cylinder(s). The spark plug is removed and compressed air is forced into the cylinder via the spark plug fitting and air bubbles will show up in the coolant of there is a leak into the cooling system.
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Have the problem with overheating addressed immediately. Running the engine with an overheat condition will cause expensive engine damage many times the cost of fixing the overheating issue.

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Did you put thermostat in backwards or water pump is bad.

Maybe your radiator is clogged.

you could have an air lock would bleed heater hoses

Some thing too check:
Make sure coolant level is up to line and clean (not dirty, do to clogged radiator, may need to be flushed or replaced).
Make sure air flow through the out side of radiator is clear (dirt, leaves, ect..) .
Make sure fan is working properly equip t (is not running too slow). Or Manual (belt driven) fan clutch is working properly, not loose or spinning too freely?
Check for broken or cracked fan blades itself.
Check radiator cap, (no gasket tears).
Could be thermostat going bad ?
Could be coolant temperature sensor/switch (from computer) going bad?
Check radiator hose(s) (too soft, may collapse)?
In some rare cases:
Timing could be off.
Could be water pump.
Could be blown head gasket(s).
Could have cracked head(s).
ECT..............Hope this was some help???

Well....deep breath.......it's not bad.

1. Check your radiator coolant level

2. Check/Test radiator fan

3. Test/Replace radiator cooling fan relay

4. Replace the thermostat

5. Check/Replace the coolant temp sensor

6. Replace the water pump.

The thermostat is behind the upper radiator hose...remove the upper radiator hose and loosen and then remove the two bolts on the outlet (where the upper radiator hose ends) The thermostat is inside that outlet...Another thing to check is if there is water in the oil...If there is water in the oil then it could have a head gasket problem..Did you ever replace the thermostat? If it is stuck then it would also cause overheating...Excessive exhaust backpressure because of a clogged catalytic converter could also cause overheating..Also check belt tension and condition. A loose belt that slips may prevent the water pump from circulating coolant fast enough and/or the fan from turning fast for proper cooling...Another thing it could be is a faulty Water pump -- Any wobble in the pump shaft or seepage would call for replacement. In some instances, a pump can cause an engine to overheat if the impeller vanes are badly eroded due to corrosion or if the impeller has come loose from the shaft. The wrong pump may also cause an engine to overheat. Some engines with serpentine drive belts require a special water pump that turns in the opposite direction of those used on the same engine with ordinary V-belts... Also check the Fan -- With mechanical fans, most overheating problems are caused by a faulty fan clutch, though a missing fan shroud can reduce the fan's cooling effectiveness by as much as 50% (depending on the fan's distance from the radiator) which may be enough to cause the engine to overheat in hot weather or when working hard.

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!

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.