Hi All, I just bought a truck and it gets hot while it idles. Its fine when driving, stays under 210, when Idles, its can get to 240-260, Then I drive it will cool down again. Any ideas what I can check to correct this? I dont know much about mechanics but I can turn a wrench Please help!!

 

Have you checked if the fan starts when the temp goes up? If not, that's the first thing to remedy.

 

The fan does come on. Any way to test to see if its bad? I don't hear a loud roaring sound from the fan when the temp gets high

 

OK, Replaced the fan clutch. It seems better but, I let it Idle for about 20 minutes and it went to about 230 deg with the air on. The AC still felt cold. I rev the engine up to 2500 -3000 rpms for about 5 sec and it cooled down some. I'm guessing thats a good thing? Would this be normal? Thanks

 

Having the AC on while on idle still makes the engine work. I assume you have the AC on because it's hot outside. Hot surrounding conditions makes less than perfect conditions for cooling.
The good thing is that your engine cools when you rev up a bit. Revving up makes the fan and the waterpump go faster. Result: better cooling!

In conclusion. Your cooler is fine. Your thermostat is fine.
If your propblem persists you may want to change the ration on the drive belt wheel at the fan, smaller wheel, more turns of the for each turn of the engine. Another source of concern may be a worn waterpump.

If not a big problem, do nothing. If it is a big problem, try speeding up the fan or make the waterpump work better (change it).

 

I had a 4.8L with this problem. I had the water pump changed and it fixed it.

 

1. loose belt slipping on pump pully
2. bad pump, "insufficient" just like the other poster said
3. clogged radiator. when you revv her up, you force coolant through it and it cools faster; when you "move" you have better air flow, and cools faster
4. a/c is well known to raise engine temp up if used continuosly due to increased load.
5. i'd suggest 2 things for starters: flush system and pressure wash radiator from the outside. dust, pollen, dirt can greatly reduce its efficiency.
6. on cold engine, open expension canister cap, start the engine, and keep looking inside the canister. you should see coolant. make sure you do so until thermostate opens, unless it shows itself right on. so, watch for bubbles bubbling out of coolant. looks like beer or champaign bubbles. if you do have those - bad luck, you have exhaust leaking into coolant through head gasket.