I have a 2005 model of Sienna with 154,000 miles. The car overheats once I switch on the AC over a short distance. With AC off the car runs smoothly. The mechanic has washed the radiator but the problem persists. Mechanic suggested we change the radiator from single cell to double cell. Please what do I do to solve the problem.. Thanks
First when the engine is cool check the coolant level. If the car behaves normaly without ac then the thermostat should be alright. Check for flow in the radiator: Start the car when cold run the car at idle till the fan comes on, the hose comming out of the bottom of the radiator should be getting hot quite quickly now. If not I suggest flushing the radiator. If the ac actually works, and the radiator is not clogged. I would suggest the following: Have a second person with you and run the car, like normal till the cooling fan comes on (Make sure it does). Then drive the car with the ac until the temp is just slightly higher than normal (don't let it overheat). Pop the hood and have the second person go out and check to make sure that both the main and secondary ac fan, is coming on. If not check the appropriate fuses and plugs. If they are both coming on or there is only one. Suggest motor/radiator flush.