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Skyvisions, ASE Certified Technician
Category: Toyota
Satisfied Customers: 14461
Experience:  Toyota Master Diagnostic
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2004 Toyota Sienna rear heater does not put out heat, fan is

Customer Question

2004 Toyota Sienna rear heater does not put out heat, fan is working , coolant level is good.
Submitted: 7 years ago.
Category: Toyota
Expert:  Skyvisions replied 7 years ago.

If you roll under the vehicle you will see 4 aluminum lines going to the rear down along the passenger side of the vehicle. Is the coolant/lines in two of these lines hot? Have you checked the coolant level in the radiator when the coolant is cold by removing the cap and checking? Or are you strictly going by the coolant level in the reservoir bottle?



Customer: replied 7 years ago.
Will have to check the temp of the lines, and yes i have just topped off the reservior. I then ran the van up to temp and the reservoir over flowed.
Expert:  Skyvisions replied 7 years ago.

If you're only topping off the reservoir you need to get to the actual radiator cap that holds the pressure in the system and make sure that the coolant is full in the engine and radiator. This vehicle is known to have major leaks in the radiator. If the heater is not blowing hot in the rear it usually is because of coolant deficiency because this is the furthest for the coolant to travel. Putting coolant only in the plastic reservoir that is incorporated into the cooling fan housing is not sufficient.



Skyvisions and 3 other Toyota Specialists are ready to help you
Customer: replied 7 years ago.
Okay, I will have to wait since i just got the van to temp. Also the lines in the back are hot, this still indicates to you insuffuicent coolant. If the answer turns out to be low coolant i must have pin hole leaks in the radiator? And this has been a problem on the 2004?
Expert:  Skyvisions replied 7 years ago.

The radiator is known to leak down along both sides. It was actually recalled in 2004 to replace the radiator. Even the replacement radiators for the recall I have seen to leak a couple or three years after installation. There are no shutoff valves for the coolant flowing to the rear radiator/heater. The only thing that controls hot or cold air is a blend air servomotor that bypasses air around the heater core.



Expert:  Skyvisions replied 7 years ago.

If you have ruled out that the coolant is circulating to the rear the only other possible option is that the air blend servomotor or controls inside the heater box in the right rear quarter panel area is malfunctioning. To gain access to this heater box assembly is quite a project. Have you double checked all the control settings front and rear? Does the heater control low straightly colder if you switch it to the air-conditioning mode? If you try and switch both heater controls from cold to hot rapidly several times can you kick it in to make it work for heat?