Overheating only when idling?

When I am cruising down the road everything is normal, temp gauge is right in the middle but when i stop and idle at a light the temp gauge starts moving up quite quickly, within 30 seconds to a minute its nearing the red zone. This just started the other day out of no where. Radiator is a year old and thermostat and hoses too. Coolant looks good, no obvious leaks, so what could it be? Thanks!

 

Fan clutch

 

^ agreed.
Pop your hood up and check out your fan (spinning fast, blowing good amount of air)

When you're moving, air is being forced into your engine bay..thus cooling down your motor.
But when you slow down (ie stop light, in traffic, etc) ~ there's no air being forced onto your engine, thus making it overheat.

So thats the job of your fan

(but, as always, there could be other problems..but that would be my best guess as well)

 

My thoughts too were on the fan clutch, but I've popped the hood to check the hoses while it was running and the fan was spinning. I had to avoid hitting my arm on the fan while i checked the lower radiator hose. Any other ideas?

 

Bad thermostat or install and or water pump bad? Is radiator new or used? Fins clean? Coolant topped off? Radiator cap good?

I had an electric fan on my 02 that I would manually turn on/off. When not moving at idle fan off it would take a while for it to get hot enough to warrant turning it on. Definitely more than 30 sec to one min...

 

I would say fan clutch. Just because it's spinning does not mean the clutch is not bad and not allowing it to spin faster and bring in more air.

 

My dads truck had a similar problem to yours. We installed a rebuilt engine V6 3vze purchased from Nippon motors into his 1990 toyota pickup with a new radiator and water pump and would overheat during idle. So we decided to play around with the idle (~8degrees) and all of a sudden the temp dropped below the half way mark (40%). We haven't had any problems ever since. This may not be the case for your truck, but worth a try.

 

With the engine off, try to spin the fan with your hand. Is there any resistance or does it spin for 1 or 2 revolution?

When the engine warms up, are both the upper and lower rad. hoses warm?

 

I'm having this same problem. If I'm at a stop, I have to put it in neutral/park and rev it up above 1200 rpm to keep it cool. If its under 1200 rpm's even when moving then it will overheat. Also, this will only occur on very hot days when temps are above 90 degrees or on long trips. Any suggestions?

Ooppss. Sorry. Wrong forum. This should've been in 2nd gen as my truck is a 2005.

 

that also sounds like a fan clutch. the fan is belt driven. but if the clutch is bad it slips even though the fan is trying to turn it. you have to rev your engine up, because only at those higher rpm's is there enough belt spin to get the fan moving enough to cool the system.

you could also check your water pump. it is belt driven too.

but whatever is failing in your truck is belt driven, hence the higher rpm's bringing it back to normal.

 

if the fan clutch is not working, when you stop at a light, the engine heat just collects under the hood. there is no fan to pull air through the radiator and cool it.

when you are driving there is constant air through the radiator cooling it.

the fan is supposed to come on at idle, when it's hot enough.

 

Along with checking the fan clutch, I would check coolant level in the radiator, and check the water pump. Low coolant levels and bad water pumps can cause the exact same issue. It seems to cool fine at higher speeds because with the engine running at a higher RPM, it will flow coolant better than at idle. Definitely check out the fan clutch though!