2002 nissan sentra losing coolant . Heat only works until coolant leaks out .Is this related to the timing belt ?

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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the water pump is on the right side of moter under plastic cover will have to take out motor mount and timing belt to replace

If, in fact, you're loosing coolant thru the tailpipe, then I'd expect you have either a blown head gasket or a cracked head.

Check around with friends, relatives, neighbors, etc. and try to get a consensus on a good local mechanic, then go to him for diagnosis.

The timing chain doesn't really have a maintenance period. They don't have a habit of breaking or stretching. Timing belts on some vehicles do have a recomended replacement period. Locate your local NTB, Firestone, or Sears for the maintenance schedule.

low coolant. check coolant level. possible that u have a coolant leak

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!

No heat is the result of low/no coolant. Some places to look for the coolant leaks: Bad head gasket, cracked head, "pinholes" in one of the hoses, leakage around the clamps, and a hole in one of the side tanks on the radiator. If your windows are fogging upon startup or you have a sweet smell inside the cabin chances are the heater core is bad.

I hate to be the barer of bad news, but may be the head gasket.

My car started with rough idle. Then very hard to start in cold weather. Next started overheating, but no output from heater. Trickling sound from behind dash board. Overflow bottle overflowing.......

I replaced the water pump, radiator cap, thermostat, coolant, fan belts, power flushed the system. Nothing worked. Some research gave me the answer.

The head gasket leak was allowing exhaust gases to enter the cooling system, displacing the coolant. After use, as engine cools, coolant is sucked back into the system and coolant seeps into the cylinder. This gets worse over time.

First thing you'll notice is the rough idle as the spark plug burns off the coolant in the cylinder. (This is especially true at low temperatures.) If it is the head gasket, the other symptoms will follow as time goes by.

well maybe there was some mis-communication there , nissan stopped using timing belts in sentra's and actually most all models in 2000 , maybe they were telling you that your serpentine belt needed changed ? but to answer your question , you do not have a timing belt in your 2002 nissan sentra . its a chain . thanks

J5

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!