4.0 sohc overheats when idling,fine with speed.

[biggiesize]

Near the end of last summer my 99 4.0 sohc started overheating if I was at a red light.It would slowly cool down after I started driving again or turned the A/C off.I replaced the Thermostat and it didnt help.Could it be the fan clutch or the serp. belt slipping?It didnt do it over the winter but with spring right around the corner,Im going to fix it before I get stranded somewhere.Any Ideas?

 

[Brandon96]

Can you confirm theres no air in the system? It sounds like there might be some. Try burping it a couple times, see if any air has gotten in there somehow.

 

[snoranger]

Check the fan clutch, check for air in the system (as stated already), check the belt, check the water pump. I had a pump that looked 100% fine, but just wouldnt flow enough to cool at idle. Replaced the pump and solved the problem. I've even seen a cracked head cause the same symptoms, but the SOHC isnt well know to crack heads like the OHV.

 

[iwannabamedic]

If not the heads, check the fan is moving enough air thru the radiator maybe clog with debris, burping could help if air is in the motor