03 only overheats with the AC running

[mattjaye2198]

I can drive all day with the windows down in cold weather or hot. I can turn the AC on and drive for 30 or so minutes in town or on the highway and after that amount of time I notice the temperature guage rise. If I turn off the AC the temperature will go down but if I keep it on the truck will overheat. I've never let it completely overheat but my wife let it get really close one day and it boiled out some coolant. The coolant level is fine and it doesn't leak. The engine oil looks normal. I am doing an air test on the reservoir today but I'm not able to do a compression test here. Has anyone experienced anything like this before? If so what did you do to fix it. Thank you for your time. I'm trying to get it fixed ASAP because I'm taking my family on vacation in 27 days and want the truck to get us there and back LOL

 

[bedrck46]

How many miles on the expy? could be a clogged radiator, bad water pump or even blockage on the radiator fins among other things

 

[bedrck46]

The engine overheats

Water thermostat.
Water pump.
Internal engine coolant leak.
Radiator.
Heater core.
Cooling fan or visctronic fan clutch.
Pressure relief cap.

B1 CHECK THE ENGINE COOLANT LEVEL
WARNING: Never remove the pressure relief cap under any conditions while the engine is operating. Failure to follow these instructions could result in damage to the cooling system or engine, or result in personal injury. To avoid having scalding hot coolant or steam blow out of the cooling system, use extreme care when removing the pressure relief cap from a hot degas bottle. Wait until the engine has cooled, then wrap a thick cloth around the pressure relief cap and turn it slowly one turn (counterclockwise). Step back while the pressure is released from the cooling system. When certain all the pressure has been released, remove the pressure relief cap (still with a cloth). NOTE: If the engine is hot, allow the engine to cool before proceeding.
Key in OFF position.
Check the engine coolant level at the degas bottle.
Is the engine coolant OK?
Yes
GO to B2 .

No
REFILL the engine coolant at the degas bottle. GO to Pinpoint Test A .
B2 CHECK THE COOLANT CONDITION
Check the coolant for dirt, rust or contamination.
Is the coolant condition OK?
Yes
GO to B3 .

No
FLUSH the engine cooling system. REFER to Engine and Radiator Flushing in this section. TEST the system for normal operation.
B3 CHECK FOR AN AIRFLOW OBSTRUCTION
Inspect the A/C condenser core and radiator for obstructions such as leaves or dirt.
Is there an obstruction?
Yes
REMOVE the obstruction. CLEAN the A/C condenser core and radiator. TEST the system for normal operation.

No
GO to B4 .
B4 CHECK THE HEATER CORE OPERATION
Install the pressure relief cap.
Key in START position.
As the engine starts to heat up, feel the inlet and outlet heater water hoses. They should feel approximately the same after three or four minutes.
Is the outlet heater water hose approximately the same temperature as the inlet heater water hose?
Yes
GO to B5 .

No
TURN the engine off. REPAIR or INSTALL a new heater core. REFER to Section 412-02 . TEST the system for normal operation.
B5 CHECK THE WATER THERMOSTAT OPERATION
Key in START position.
Start the engine and allow the engine to run for 10 minutes.
Feel the inlet and outlet heater water hoses and the underside of the upper radiator hose.
Are the upper radiator hose and the heater water hoses cold?
Yes
INSTALL a new water thermostat. TEST the system for normal operation.

No
GO to B6 .
B6 CHECK THE COOLING FAN OPERATION
Key in OFF position.
Carry out the cooling fan clutch or visctronic fan clutch component tests. Refer to the Component Tests in this section.
Is the cooling operation OK?

 

[mattjaye2198]

180xxx miles on it. I have run down the list checking everything one by one and I've eliminated
1. I have no air coming into the reservoir with the cap off.
2. The top radiator hose stays cool until the engine reaches a high operating temperature (I'm not sure on the exact temperature).
3. The clutch fan feels like it is operating correctly. (I'm not sure how to be positive it is functioning at higher rpms)
4. The radiator is not covered and doesn't have any debris on the fins blocking air flow.
I'm at the point now where I'll be taking it back to the dealer where I bought it because any other steps to find out the problem involve actually removing or flushing systems and I don't want them to think I've caused the problem. Thanks for your time. I'll be posting here regularly in the future!

 

[bedrck46]

Matt Kindly post an update when you get the problem resolved It will be a help for others. I would think the T/Stat or Water Pump may be the fault.

Don't let the dealer keep replacing parts to find the problem But with the mileage on the expy a new pump and T/Stat wouldn't do any harm

 

[bedrck46]

One thing you could do it get yourself a Bluetooth OBDII scanner and the Torque pro app. Would and should cost less than $25.00

 

[Copper93]

It sounds to me like your fan clutch had gone or is going bad.

 

[stamp11127]

Since the temp rises when your on higway that will come from: bad water pump, clogged radiator, collapsed lower radiator hose or partially open t stat. Any rust in the coolant?