Need Help! Truck overheating after being on the interstate for 400 miles of running regular temp, the temp increases dramatically when off the highway and stopped for gas. Water level fine. Fan replaced one year ago. Back on the highway, engine cools right back down when at speed.

Doesn't always increase in TEMP at slow down or stopped. Kinda stumped. Thanks for any help/advise.

Randy

 

sounds like a fan clutch issue to me

do you hear the fan roaring when it overheats? It should get really really loud when its in full lockup

 

x2 on fan clutch. when you're on the interstate you have air being forced through the radiator, but when your at stop the fan isn't keeping up causing you to overheat.

 

Thanks for the responses. NO, I do not hear the loud roar. It does do that every now and then when I start the truck. I guess my 1 yr fan could certainly be defective. I'll RE-replace it. Thanks.

 

also check thermostat.

 

failed thermostats can't cause overheating, just over cooling

 

i could have swore it was overheating... but if his fan roars like he claims it does when he starts it id say it is ok. Am i right? because that would indicate the clutch system on the fan is still in tact. seldom do i hear my fan kick on when i am in the pastures checking cattle, and im driving through grass that reaches over my hood, cutting off air flow.

 

its also possible he has a clogged radiator, allowing enough cooling with the highway airflow, but overheats at slower speeds

 

The fan clutch is heat sensitive. It WILL run and roar after startup, then cut out. It should cut back in when the temperature rises to a certain point.

When you are sitting and it's running hot, it DEFINITELY should be running and roaring.