help no heat?

[bobbyjoes]

Hi, i was on way to work and all of sudden no heat ,the fan works on all settings but even on high it blows cold air, the antifreeze was a little low so added some ,still no heat ,thanks in advance for your help

[big white bufflo]

one of the cheapes think you can do for diognastic is to replace the thermostat first it could be stuck open witch would cause no heat you did not say year of car and if it has dual zone control

[bobbyjoes]

sorry, its a 1998 buick lesabre,no dual controls ,thanks so far

[imidazol97]

Originally Posted by bobbyjoes

Hi, i was on way to work and all of sudden no heat ,the fan works on all settings but even on high it blows cold air, the antifreeze was a little low so added some ,still no heat ,thanks in advance for your help

#1
This is within the years that upper intake manifolds can leak. You also might have a water pump leak or a leak at the plastic elbow that comes out of the lower intake manifold (metal) and goes to the heater lines.

So when the car has cooled to be safe, take off the radiator cap and check to be sure there's enough coolant mix in the radiator. It may be low and not pulling coolant back in from the reservoir. A low radiator may leave air in the heater core, which would give you little heat.

If your radiator is low, fill with coolant mix then start motor and be sure the coolant level stays up. If it starts to expand and overfill (normal) put radiator cap back on.

To get air bubble out of radiator: after engine is thoroughly warm from driving, rev motor to 2500 rpm for 10 seconds. Repeat 4 more times. I do this with the car on an uphill slope so the heater is lower than normal, hoping that helps air leave the heater.

Then let the motor cool. Then recheck radiator level. Last is to bleed the thermostat housing with the little screw on top of the housing. Let air out until coolant starts to dribble out.

After you have the radiator system stabilized, then watch the level of coolant in the reservoir to see if you are losing coolant.

#2
You might have a heater core that is partially blocked.
After you know the coolant level is full when the motor is running and warm, turn blower motor on fast and after a minute check the temperature of the two heater hoses. It helps if you have someone hold the idle about 1500 rpm. The inlet and out let hoses should be about the same temp. If one is definitely cooler, that means the coolant flow is slow and the air over the heater is taking out much of it's heat and the metal of the heater core is cooled.

When the flow is fast enough, the air over the heater takes out heat but the hot coolant is being replaced fast enough to keep the metal heater hot.

[bwhitney1256]

Same car and problem here. No coolant leaks at all and coolant level is good. Going to start by replacing the thermostat.Hope that is all that it is.

[dpalomaki]

A couple more thoughts?

If the t-stat is stuck open, you will eventually get some weak heat, especially if the car is idling and not driving/forcing air through the radiator.

If there is NO heat, feel the heater hoses at the firewall. If they both are hot and about equal temperature, you probably have flow through the heater core, but the blend door may be stuck on the cooling position - no air passing over the heater core, just over the A/C coil, and thus no heat.