Frustrating cooling system problem.

[sepehr]

Here's the problem I'm having:

- At idle, the engine temperature climbs slowly past the 1/2 mark on the gauge. This also happens when I am slowly climbing a hill at lower rpm.

- The heater starts blowing cool air when the revs drop below 2000rpm. Higher revolutions = more heat out of the vents.

- Water pump is new, thermostat is new. The fan clutch could be bad, but I can't see how this has anything to do with the heater.

I've repeatedly bled the cooling system. Is there a trick to it? Here's what I'm doing:

Let the engine heat up till the thermostat opens.
Open the bleed screw.

Coolant comes out, but only when I rev the engine. The coolant level disappears from sight in the bleed hole when I don't rev the engine. The level in the reservoir remains constant.

If I open the reservoir cap when the screw is removed, coolant comes out easily.

Any suggestions/ ideas?

[ak96ss]

Here's the problem I'm having:

- At idle, the engine temperature climbs slowly past the 1/2 mark on the gauge. This also happens when I am slowly climbing a hill at lower rpm.

- The heater starts blowing cool air when the revs drop below 2000rpm. Higher revolutions = more heat out of the vents.

- Water pump is new, thermostat is new. The fan clutch could be bad, but I can't see how this has anything to do with the heater.

I've repeatedly bled the cooling system. Is there a trick to it? Here's what I'm doing:

Let the engine heat up till the thermostat opens.
Open the bleed screw.

Coolant comes out, but only when I rev the engine. The coolant level disappears from sight in the bleed hole when I don't rev the engine. The level in the reservoir remains constant.

If I open the reservoir cap when the screw is removed, coolant comes out easily.

Any suggestions/ ideas?

Lift the front of the car and try bleeding again. It sounds like you still have air in there.

Did you flush the cooling system with the heater on when you changed all that out? And you are bleeding it with the heater on, right?

[sepehr]

The heat knob is cranked when I'm bleeding it. I read the blower has to be on the first setting, but I don't see how that would relate.

[individualist]

Try checking the thermostat valve between the engine and the firewall. Mine was plugged and not opening all the way which caused me to have symptoms similar to what you are experiencing. This valve will be inline with the heater core inlet hose on the main ports and will have a smaller OD hose coming to it off of the discharge side of the core. The smaller hose is what opens the valve by sensing coolant temperature but if the valve is plugged at that smaller port, the valve will remain closed or partially closed. I simply took it out and put hose barbs in it's place and all my heating issues went away. This could also cause you to have air trapped in the core by not letting full coolant flow thru the core to drive the air out.

I believe this valve was a recall or addition to the vehicle after they were produced. I gather this valve was installed to cut flow to the heater core if the core were to burst in the cabin and prevent scalding of the occupants.