Runs hot after battery replacement - Toyota Nation Forum : Toyota Car and Truck Forums

bertherr · 11-30-2006, 09:50 AM

2003 V-6 XLE 70k miles now runs hot, only at highway speeds, after having to replace the battery. The temperatur gage indicates hot & the coolant bubbles in the over flow container. I replaced the thermostat but, had no improvement. I took it into a private shop and had them check the cooling fans & sensors. All checked out fine. The coolant is original but, looks clean and is full.
Could it be the water pump? It does not appear to leak or make noise. Are there any possible connections to changing the batttery? Thanks, Bert

gdanaher · 11-30-2006, 11:40 AM

There is just no reason that the new battery would be related to the heating problem, but check the voltage at the battery with the engine idling and no load of substance on the alternator. Voltage should be around 14. I would ask why the battery was replaced...if the voltage is much above 14.5 volts then I would offer that the temp sensor might have been damaged, but this is not likely since you say that the coolant is boiling out into the overflow. The electric fans should be running constantly when the engine is hot like this so verify this yourself. Get it hot and then pull over, pop the hood and take a look. Make sure the air conditioning is not running. Secondarily, see if running the air conditioner will cool off the engine. Perhaps the fans running to cool the condenser would also cool the radiator coolant by default if the other sensors aren't working consistently. Consider replacing the radiator cap. I've had them fail over time and not hold the pressure. Look at the front end and make sure that you don't have crap covering the air flow to the radiator, like a piece of newspaper that might have been lodged up in there. I'm not familiar with this engine, so if the water pump is belt driven, then check the tightness of the belt to see if it is slipping, but again this seems unlikely.

bertherr · 12-07-2006, 07:53 AM

Ends up that the shop I took it to did not do a good job of checking the fans and sensors. I checked to see if the fans were running while the gauge indicated that the eninge was running hot. The fans were not running. They came on when I switched on the A/C and the engine returned to it's normal operating temperature. Thanks for the tips. Bert

gdanaher · 12-07-2006, 09:44 AM

Glad you found something in that laundry list of ideas that worked for you. What I don't get is why the shop unhooked the fan wiring? They only needed to replace the battery and that should have involved unclamping the battery and the removing the lugs on the top. Weird.

bertherr · 12-07-2006, 10:38 AM

I replaced the battery myself. I did not disconnect the fan wires. My wife tells me a few days later that the car is running hot once she is on the highway. I change the themostat & radiator cap after checking the coolant level. I then take it to a repair shop to get the fans & sensors etc checked out. They tell me all is fine but actually the sensor that tells the fans to come on was actually causing the problem. Bert