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Skyvisions
Skyvisions, ASE Certified Technician
Category: Toyota
Satisfied Customers: 14357
Experience:  Toyota Master Diagnostic
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I have an '06 Corolla with very little heat coming into the

Customer Question

I have an '06 Corolla with very little heat coming into the cabin. Replaced thermostat and no improvement. Flushed heat core and saw good flow but it was no help. The interior controls all seem to work but I have not been able to find a heater control valve.
Submitted: 9 months ago.
Category: Toyota
Expert:  roy replied 9 months ago.

good evening my name is ***** ***** I will assist

are both heater hoses hot under the hood???

Roy

Customer: replied 9 months ago.
I get a slight amount of heat with the heat control on its highest setting and noticeably less heat with it positioned on the cold setting. The blender control cable and lever seem to work and I can hear the door hit both extreme positions when I quickly move the control to each extreme.
Customer: replied 9 months ago.
I can not locate a heater control valve either under the hood or under the dash.
Expert:  roy replied 9 months ago.

there is no heater control valve.

both hoses are the same temp under the hood???

Roy

Customer: replied 9 months ago.
They seem to be very close to the same temp when touching them with the lower one maybe slightly lower in temp.
Expert:  roy replied 9 months ago.

if all controls inside are working and you can hear the doors work back and forth, then the heater core may still be the issue. I would remove the hoses and use a garden hose to run water through both sides of the core to force any dirt out that may be preventing proper circulation. even though you see circulation it does not mean the core is clear.

Roy

Customer: replied 9 months ago.
I ran water through it yesterday. It was very clean - nothing dark as the color started with green anti freeze and changed to clear water and it flowed easily. From what I can see the entire system is very clean so I didn't expect a clog but I flushed it just to be sure.
Expert:  roy replied 9 months ago.

ok, I still think your issue is at the core.

I will opt out and see if anybody else has any idea

Roy

Expert:  Skyvisions replied 9 months ago.

We need to confirm that the water pump is in fact pushing water through the system. You can do this one of two ways get the engine up to operating temperature without the radiator cap on and see if coolant is being pushed into the upper tank and flowing through the radiator. The ideal way to do this is to remove the thermostat install just the gasket then hold the engine RPM at 2000 RPM and see if water is being pushed through the radiator very quickly. If it is the water pump can be ruled out. At that point reinstall the thermostat I know you run water through the heater core but 99% of the time that will not flush anything on the heater inside the vehicle. More than likely going to find that the heater core is clogged on most of the tubes. Even though you have flow it's only going to a few tubes versus the entire heater core. You will need to replace the heater core. If you're getting flow since the system is full of water carefully remove the hoses from the heater core, Then start the engine up and see if water is pumping through the heater hose going to the heater core. If it is then this rules out any type of restriction in the hoses or the block itself. That brings us back to the heater core again and it will need replaced.

Customer: replied 9 months ago.
Thanks for the suggestions. I removed the thermostat and reconnected the lower radiator hose to the engine block. Then I disconnected the upper radiator hose at the radiator and filled the radiator with water until it ran out of the upper radiator hose opening on the radiator. I started the car and only saw a small amount (less than half a cup) come out of the upper radiator hose when I let the car idle at approx 1500 rpm for one minute. I then ran it at 2000 rpm and did not get any more water to come out of the upper radiator hose.
Expert:  Skyvisions replied 9 months ago.

You need to make sure that you have no air pockets in the block what I need you to do is fill the engine up completely without the thermostat and all the hoses connected. Hold the engine RPM at 2000 RPM you should see water flowing through the upper radiator tank when you look into the filler neck. If you try and pinch the upper radiator hose at that point you will feel the water rushing through the hose and it will surge out the upper radiator tank filler neck when you release the upper radiator hose.

Customer: replied 9 months ago.
When operating this vehicle prior to removing the thermostat today, the temperature was always at its normal position on the temp gauge once the engine got up to temperature. I am wondering if that temperature should have been moving up and down on the gauge rather than being rock solid on the gauge if the water pump is not pushing fluid through the system.
Expert:  Skyvisions replied 9 months ago.

If the impeller on the water pump was bad the engine would be overheating. It is not likely that the water pump is the problem. With the thermostat in the temperature gauge should rise up to about midpoint within five or 10 minutes of driving. The thermostat out the temperature gauge will be stone cold because there is nothing to slow the coolant down in the block.

Customer: replied 9 months ago.
I no longer suspect it is the water pump anymore as I removed it and it rotates smoothly and the impeller is solidly attached to the shaft and it is not damaged in any obvious way.
The temperature gauge does rise up to the midpoint with in 5 to 10 minutes of driving and stays in the same spot during all further driving with the thermostat in place.
I did not check the temp gauge when I had the thermostat out as I expected it to be stone cold as you suggest.
Should I check to see if there is good water flow to the heater core? I expect I should remove the thermostat again to run this test safely with cold fluid.
Expert:  Skyvisions replied 9 months ago.

Yes on the flow from the hoses to the heater core but have the tstat in it will push fluid that way to the hoses.

Customer: replied 9 months ago.
Turns out that I had trapped air in my system and once I "burped" it the heat started working.
Expert:  Skyvisions replied 9 months ago.

That is good to hear. Please do not forget to rate the assistance that I provided you at three or higher.