Car temp runs hot then cools up & down


#1

Hi guys,

My wife has a 2001 Nissan ultima GXE with 89,000 miles. The car seems to run hot with the temp gauge reaching the “H” but never passes it, andwhen air conditioner is on it blows hot air; Then the car cools down it the air cools again, and this seems to happen all of the time.

Now, it’s been happening for at Least 3 months, during this time it has had a tune up, the radiator flushed & hoses, thermostat replaced & lastly the … Sensor has been replaced & still the same thing happens the car temp runs hot cold up then down. We are at a loss her and have run out of ideas. Any help please

Marco


#2

What is a " … Sensor?" I would assume engine temp sensor, but I could be wrong.

What is she doing when the car heats up? What is she doing when the car cools down?

If it heats up at stoplights and then cools down when the light turns green, it’s time to look at the fan.


#3

Your coolant is low and your engine is overheating.

There are a list of possible root causes:
stuck/stickly thermostat (good probability)
bad gummed up rediator (modest probability)
failing rediator cap (low probability but cheap to fix)
blown headgasket (low probability and expensive to fix)
air in system (not a root cause, a manifestation of a root cause)
coolant leak (reasonable probability)
collapsed hose inner liner (low probability, cheap to fix)
failing water pump (modest probability, expensive to fix)

Yeah, we can edit again!!!


#4

“and when air conditioner is on it blows hot air; Then the car cools down it the air cools again, and this seems to happen all of the time.”

Check that the electric cooling fans are operating properly. Turning on the A/C forces them to turn on, but they should also run by themselves before the over-heat point is reached…