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I have a Lexus RX300 which used to be warm and toasty inside. Now, all of a sudden, I have little heat on the drivers side and no heat on the passenger side. The blower still blows strong and the AC works fine. I was told I needed to replace the heater core which will cost about $1000.00. I did some asking around and I was told that in my car, a flush of the cooling system will correct this problem 70% of the time. I have no idea if this is true but I do know that I'd rather not spend $1000.00 if I do not have to. Do you think it is worth it to try the flush? Any advice you can give will be appreciated.

Answers from the Automotive Experts

Amanda J. Pierce, MBA Chillin, Thank You for writing into ask patty, typically a coolant flush will not repair a failed heater core. Coolant flushes are indeed recommended about every 30k miles according to your manufacturer recommendation. That is a good point to remember in the future as this is a preventive maintenance measure. The replacement of a heater core is an evasive procedure due to the fact of its location in the vehicle, they require extensive labor time, this where most of the cost of replacement factors in to your $1000 estimate. I do recommend to continue to call around for estimates to find a more competitive price if you can, but you should replace the heater core if it is faulty you will have about an 80% coolant flush in this replacement since coolant will need replenishing in this operation anyhow. On a second note, you may have a faulty HVAC cable, in this I mean, when you switch from cool to warm air, your ducts have doors on the inside of the dash. If this cable is disconnected it can not allow warm/cool air, depending on the situation, to properly circulate throughout your system.

Judy Curry, Co-Founder and Vice President of Marketing at Currys Auto Service Prior to flushing it would make sense to have a technician check to make sure the thermostat is opening at the correct time and the cooling system is getting to full operating temperature. Also make sure that the cooling system is full. If the cooling system is low the loss of heat is usually one of the first symptoms. If all checks out well, then I would definitely try to flush the system. This is something that should be done every two years anyway and is often overlooked.

Laurie Sarno, Co-Owner at Super Girls Auto Hello Chillin- I would first start by changing the thermostat- ( I have changed 7 this past week with the cold temperatures) - it is a very inexpensive repair- then if that does not work try flushing the cooling system- I hope you do not have to replace the heater core- hope this helps - thanks Super Girls Auto.

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