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95 Maxima Heater - lots of air, no Heat

My 95 Maxima is not blowing any heat into the passenger compartment. I''ve flushed the cooling system, and ran a hose from the intake line of the heater core so that the water ran out the disconnected hose, so I'm pretty confident there's no blockage. This was all done wihtthe t-stat removed as well so that I got complete flow through the engine.

At idle when the car is warm, I get about 102F on the surface of the hoses going into and out of the heater core. The air however coming into the passenger compartment is still cool. When I move the temperature slider from cold to hot, I can feel that there is an extra load on the blower and the flow is decreased through the vents. I get a little feeling of warm air, and then it goes cool again.

Is there something else that coud be blocking the air from going over the heater core? I've also read about a vacuum connection - what is this?

Any suggestions woudl be greatly appreciated.

Thanks,

-Dan

Reply to
dfscharpf
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102F doesn't sound very hot. Are you sure the thermostat is working correctly? If it isn't closing, the water just runs though the engine and never really gets hot.
Reply to
E Meyer

Since I've removed the Thermostat to flush the system, shouldn't I at least feel warm air coming out of the blower when I turn on the heat? The temperature gauge is reading above normal while I idle so I should be getting something that's warmer than the 60F garage air?

The 102F that I'm reading is on the outside of the hose using a thermocouple attached to my multimeter, so I would think that the fluid woiuld be a little warmer in the tube.

I think I'll test teh t-stat and stick in a new one to test your theory? I'll let you know. - Thanks for the suggestions.

-Dan

Reply to
dfscharpf

What's the temp gauge say?

Reply to
JimV

....the air from going over the heater core? I've also read about a vacuum connection - what is this? Theres a air mix door, see below. Manual system has manual wirectrl. Autoclimate, motor actuated... If door is open, cold gets in regardless of heatin.

Vacuum 'piston' actuates the coolant flow valve. Electrically controlled.

Check out:

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Reply to
Wiikinki

I've finally had some time to get back to this so I've done the following:

I've replaced and installed the new t-stat, and that didn't change anything.

I now have a clear tube connected to the hose that brings coolant into the heater core so I can see if there is coolant moving through it. When I start the car, coolant runs freely. When I turn the heat off (slide the control to "cold") the coolant stops flowing through the tube - as it should.

When I get to running temperature - the gauge is at the midway point - there is no coolant running into the heater core which means it isn't heating up which is why I have no hot air coming into the cabin.

I would think that if the water pump is defective, the engine temperature would just climb.

Any ideas on why I'm not getting flow into the core when I'm at running temperature?

Thanks,

-Dan

Reply to
dfscharpf

Reply to
veefer

There is a coolant check valve that controls flow through the heater core. Sounds like that valve isn't opening up.. It is electronically controlled.

A stuck open thermostat would have prevented your car from reaching correct operating temp (assuming it's cool where you live and at highway speeds).

A stuck closed thermostat would have likely caused your car to overheat (at idle for example) - so your problem has nothing to do with the thermostat.

Given that you don't see any coolant flow, it's most likely to be:

- a bad control valve

- a clogged heater core

It could also be a bad connection to the control valve from the HVAC controls.

Nirav

Reply to
njmodi

This happens at least when bleeding has not been done properly. Air pockets hinder flow; also cause heat spots which will warp engine heads.

Some cars [maxima] with complicated tubing, air bubble problems: loosen heater hose so that coolant drips, air escapes. Drive one hour (keep) engine above 2k rpm. Top coolant as necessary. Close hose... I suppose FSM tells to raise front, idle while bleed scre open.

Reply to
Wiikinki

As said, the valve el. ctrl & vac pwr details are explained here. For -95 bleed valve & procedure, check 'Favorite Links', all info via clic clic:

see

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Reply to
Wiikinki

Yes - you may definitely have air in the cooling system. Although I would expect to see some over-heating in that case too..

The way I've always bled most of the air out (when replacing the coolant) is to start the car and let it idle with the radiator cap removed. Once the coolant starts flowing through the engine (thermostat opens), the air tends to work itself out of the system and escape.

You still have to top it off after a short drive as Wiikinki mentions.

Nirav

Reply to
njmodi

You guys got it right! It was air in the system. Once I got this filled up, the heat was back.

Thanks for the help!

-Dan

njmodi wrote:

Reply to
dfscharpf

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