Purchased O4 LS 430 last spring with 62,000 miles, now has 81,000. Car has performed well. Drove vehicle to New Orleans and Mississippi Gulf Coast last July. Car over-heated once and threatened to do so on many occasions. Took it to dealer twice and they could not find a problem. After returning home in Wisconsin had dealer flush cooling system and change thermostadt. Problem presisted. No problems in cold weather. Now that weather is warming can't wait in traffic more than a few minutes before temperature gage begins racing to the red-line. Then, it quickly returns to normal at regular driving speeds. Does anyone know what is causing this problem? Never had this problem with LS 400 that I drove for nine years. I pride myself in keeping a well-maintained vehicle that can be driven to California on a moment's notice. Worst of all, I have a wife who makes snide comments about the "fancy car" and how her Mitsubishi Galant never over-heats. Ya-da, ya-da, ya-da!!! Help!!!

 

Sounds like a the thermostat is stuck or the fan switch...i'd start with the thermostat...also check your fluid level in the radiator & overflow tank.

 

if you had the thermo and fluid changed after the problem started, like you stated, then I would check to make sure the fan is turning on. I would think a dealer would catch this problem if you took it too them with over heating problems though. Way to obvious.

 

i'm not sure if our cars have 2 fans or just 1, i haven't looked so closely in the few months i owned it, but i had an old car with 2 fans and only one was turning on when both should have and many mechanics failed to notice that this was the problem...

 

i think it might be the fan too..i had my electric fan fail on me once during the summer in NYC...i had to stop the car SO many times and once i made it to the Highway, temps went back to normal.

 

i had this same problem with my LS400 after i got the timing belt done...Problem was with the coolant reservoir pipe, it was blocked pretty bad...so there was no coolant going through the system and it made the car overheat. If i were you i will take it to the dealership and have them check the water pump, coolant pipe, thermostat....i don't see it being Headgasket problem with only 81k miles...Never heard of any Headgasket going out on 3uzfe motors as they are rock solid.

 

Also as others have said, make sure to check the cooling fans if they come on or no...There is a temperature sensor in the radiator that kicks the cooling fans on.

 

Just noticed the other day that my electric fans weren't turning on. Where exactly is the temp sensor on the radiator? Is it difficult to change?

 

[QUOTE=Muddywater;4505291]

Purchased O4 LS 430 last spring with 62,000 miles, now has 81,000. Car has performed well. Drove vehicle to New Orleans and Mississippi Gulf Coast last July. Car over-heated once and threatened to do so on many occasions. Took it to dealer twice and they could not find a problem. After returning home in Wisconsin had dealer flush cooling system and change thermostadt. Problem presisted. No problems in cold weather. Now that weather is warming can't wait in traffic more than a few minutes before temperature gage begins racing to the red-line. Then, it quickly returns to normal at regular driving speeds. Does anyone know what is causing this problem? Never had this problem with LS 400 that I drove for nine years. I pride myself in keeping a well-maintained vehicle that can be driven to California on a moment's notice. Worst of all, I have a wife who makes snide comments about the "fancy car" and how her Mitsubishi Galant never over-heats. Ya-da, ya-da, ya-da!!! Help!!!

 

My 2004 LS 430 over-heated because the electric fan control unit ($45.00 part), coolling fan control module ($402.00 part) and the cooling fan relay unit ($97.00 part) which send signals to the the cooling fans were burned out. Multiple diagnostic tests at three different dealerships did not reveal this problem. A smart technician at Tires Plus connected the cooling fans directly to the power-supply and both worked. Then, he checked all of the units mentioned above and discovered they were not operational. As you face the front grill of the vehicle, the electric fan control unit and the cooling fan control module are located under the hood left of the main cooling fan, just behind the grill assembly, beneath a black plastic cover. The cooling fan relay is positioned immediately across from these two units in a panel with what looked like other relay devices.

Now that my cooling problem has been resolved, I hope this information will be of help to someone else. Thank you! Muddywaters.