Question about 2004 Nissan Sentra

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How to bleed coolant system in a 2003 nissan sentra GXE 1.8L?

I believe that there is air in the lines or even a block that is not allowing coolant to reach the heater core. This is most likely causing my heater to not work and my temp. guage fluctuating from normal temp. to hot. I have tried bleeding air out of the radiator by letting it reach temp with the radiator cap off and that seemed to get some air out, but doesn't solve my problem. Trying to locate the heater bleeder valve. Any suggestions?

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  • Laura Traverso Dec 07, 2012

    haha nevermind! just located it!



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Posted on Jan 02, 2017

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SOURCE: 2001 sentra heat problem.

There is a bleeder bolt next to the thermostat housing...I believe it is 10mm...Its on the block....Has a small sticker that says dont open when hot..Its very small, hard toe read....The bolt has 2 small copper washers on it to make the seal....I would try to bleed it from there...

Posted on Feb 12, 2010

  • 88 Answers

SOURCE: 2003 Nissan Altima. A/C quit & engine overheated.

verify the radiator fans, fuses, relays of fans. when you turn on the a/c all the radiator fan turn on too, if not you have a problem with it.

Posted on Jun 01, 2010

  • 5081 Answers

SOURCE: trying to locate the coolant temperture sensor on

Engine coolant temp sensor should be on the drivers side of the engine block. Follow your top radiator hose from the radiator to the engine block. near that you should see a sensor (it has a clip on it where the wires attach).

Posted on Feb 16, 2010

  • 4070 Answers

SOURCE: I have an 1996 Nissan Sentra GXE i live in ND and

Sounds like it's the air control flap which determines the mix of heated and fresh air. This could be vacuum controlled or manually with a cable.

Posted on Jan 10, 2011

  • 360 Answers

SOURCE: how do u bleed the

Most modern day front wheel drive vehicles have at least one (and sometimes, 2) bleeder screws. They are typically located at or adjacent to where the upper (and lower ) radiator hoses attach to the block. Open them slightly and start adding air is forced out the liquid level will rise. When you get liquid from the bleeder screw, you can then close and tighten.

Posted on Feb 06, 2011

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Heater blows cold air--where is heater control flap or switch?

These cars are notorious for having blocked heater cores, causing the heater to blow cold air. That's because there is a heater core bypass hose near the firewall that allows the coolant to bypass the heater core. Eventually the heater core fills with gunk and no coolant passes through it. You'll need to disconnect the hoses from the heater core at the firewall and flush the core using a garden hose. Flush both ways till water runs clear. If you can't access the heater core fittings at the firewall, then follow the hoses from these fittings back to the engine and disconnect them at that point and flush from there. If you flush from the hoses in this manner, it is important that you clamp off the bypass hose at the firewall with a vice grip pliers.
Otherwise the flushing water will go through the bypass hose and not the heater core.


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Most likely the thermostat broke. I expect that you have an older Hyundai and never had the anti-freeze changed. When the engine is cold the thermostat is closed which causes the engine to warm up more quickly. A warm engine runs more efficiently (less gas) and more smoothly. When the engine temp reaches a certain temp the thermostat opens and then allows the hot engine coolant to run through the lines to the heater core. The heater blows air over the heater core which produces the warm air that warms up the cabin. Thermostats used to be cheap and easy to change. I would suggest a web search for how to replace the thermostat. Something like 'hyundai accent 2002 replace thermostat".

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1. Blocked or malfunctioning heater core assembly.
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4. Malfunctioning blend door.
5. Rust or radiator sludge build up within the heater core assembly.

I would suggest to have all areas above inspected for possible mentioned faults, if possible. I would personally start with the heater core. Maybe a back flush at this area would do the trick. Move on to the coolant system flushing procedure, if the core inspection proves that the device is functioning correctly and is allowing coolant. to pass.

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