Engine Overheating - Toyota Nation Forum : Toyota Car and Truck Forums

quadrupletreehotel · 09-22-2011, 11:59 AM

Whenever I turn on my AC my engine starts to overheat. Afterwards the check engine light will come on. At first I thought I had an antifreeze leak but that doesn't seem to be the case. When I took it to the mechanic he said that the catalytic converter is faulty and this is causing the problem. I have my doubts though because the overheating only happens when the AC is on. Would a faulty catalytic converter cause engine overheating? and at that only when the AC is on. When the AC is turned off the engine runs fine.

Felixs10 · 09-23-2011, 11:49 AM

Do BOTH of your cooling fans turn on when you turn the AC on? Both should turn on . If not check battery voltage at the plugs for each fan (be sure to use the ground from the plug not the car).If you have voltage and the fans arent turning, Then your fans are no good. If you dont have voltage the check the associated fuses and relays. Your check engine light might be coming on simply because your car is overheating. Either way you dont want the car to overheat !
If the fans are found to be the problem , a simple EBAY search will yield you the complete shroud assembly with fans installed and wired for under $100.00 .
Let us know how you make out

quadrupletreehotel · 09-24-2011, 08:03 PM

Both of the fans are working fine. I found that the antifreeze levels drop when I run the AC but I can't see a leak anywhere. I don't see any blue smoke out of the exhaust or buildup in the motor oil inlet. Is there anywhere else the antifreeze could leak into without dripping onto the ground?

fishexpo101 · 09-26-2011, 03:33 PM

If the car is burning coolant, the smoke coming out the tailpipe will generally be white or even have no color, depending on how much is being consumed.

Antifreeze level should not drop for any reason - sounds like there might be an air bubble in the system. Which coolant is in the car - is it the factory Toyota Red coolant or the universal green stuff. Hopefully not a mix of the two.

To rule out a blown headgasket - have the oil chemically tested for trace coolant, have a gas analyzer set over the top of the radiator to see if exhaust gases are bubbling through the cooling system. Is suspect is the latter, exhaust gases are leaking into the cooling system, creating the gas bubble. That bubble works is way out and pushes some coolant out to the recovery tank.

Quick way to check is to verify coolant level at the radiator. Then fill the coolant reservoir tank to the 1/2 way mark. Drive and see if the coolant level in the reservoir tank has changed (after the car as cooled down).

If there is more coolant there, then exhaust gases have pushed the coolant out, likely have a blown headgasket or other cooling issue. If there is less coolant in there, then the engine is consuming coolant, again possible blown headgasket or other cooling system failure.