Van overheats, but only at idle – 2004 GMC Savanna 3500

ANSWER : Hello. Assuming that you replaced the fan clutch and the fan is actually working, I think you are on the right track as far as the radiator being clogged. When the vehicle is not moving, it does not have the same air flow that it does when the vehicle is moving. Due to the lack of air flow at idle, a clogged radiator would cause the vehicle to overheat.

When the vehicle is moving, the extra airflow passing the radiator might be just enough to prevent the vehicle from overheating even if the radiator is clogged. I would recommend getting the radiator tested for hot spots with a laser thermometer. If any hot spots are found, this would indicate that the radiator is clogged somewhere and the overheating would certainly be cased by this. If any hot spots are found, I would recommend having the radiator replaced by a qualified professional, such as one from YourMechanic. Once the radiator is replaced, the vehicle should no longer overheat.

ANSWER : Hi there. This can be caused by the issues that you mentioned or a number of other things. You need to make sure all of the connectors are making good contact. I would then need to know what codes are in the computer to know if this is a circuit issue or not. Most of the time, it is not the circuit but instead a vacuum leak.

If there is a vacuum leak, then the vehicle will act like this and the computer cannot control the idle. Most of the time it is a bad hose or an EGR valve that is stuck open. That is the most common cause for this. I typically remove the EGR to check it to feel the diaphragm on the bottom of it to see if it is moving correctly. If you need to have this repaired, consider YourMechanic, as a certified mechanic can come to your home or office to diagnose and repair your car’s idling issue.

ANSWER : Hello, thank you for writing in. The vehicle is struggling to keep up with all of the different accessories when the engine is idling. This is typically due to an issue with the air intake, fuel intake, or the sensors that monitor and control them. Start by having the vehicle scanned for codes at your local automotive parts store, or by a different technician. If no codes are present, attempt to clean the throttle body, idle air control valve, and the throttle position sensor. If there are codes present, then you can use them to point you to the issue at hand, and take corrective action from there. For more help with diagnostics or resolving the issue, contact our service department to schedule an appointment.

ANSWER : Hi there. The engine has a vacuum leak and is causing the engine to stumble down on the idle. Check all of the vacuum hoses and the brake booster for any leaks. The engine is rich for it’s not burning all of the fuel properly and may also have bad spark plugs. If you need further assistance with engine not adjusting the idle, then seek out a professional, such as one from Your Mechanic, to help you.

ANSWER : Check to make sure the fan clutch is working by getting the van warmed up good and using a tissue in front of the radiator center have someone raise idle to 2000 rpm and put tissue on the front of radiator and it should stay there. Then let the engine idle to see if the tissue falls or stays in place. If it falls then replace the fan clutch. If it does not fall and stays in place then you may have water pump issues. For a more thorough inspection, enlist the help a certified mechanic, like one from YourMechanic. They can come to your home or office to diagnose the overheating issue and help with repairs.

ANSWER : Hi there. The fact you able to get the idle speed to drop by tapping the gas pedal, lead me to believe the high idle is due to a sticking accelerator cable. Another possibility could be, a faulty throttle body not allowing the throttle to return to the closed position. Proper diagnoses should be performed to avoid unnecessary repairs. I recommend having your vehicles high idle be diagnosed and repaired by a certified technician, such as one from YourMechanic.

ANSWER : The heater not working in some cases may be related to the overheating problem you are also having. This may be due to a faulty heater blower motor or potentially a bad heater core. As you may know, the heater core is a small radiator like unit that circulates the hot coolant from the engine through the heater core which then uses this warm coolant to heat the inside of the car with the help of the blower motor that blows the warm air through the vents inside the car. When the cooling system is not properly circulating coolant through the motor, this results in the warm coolant not being pumped through the heater core properly in order to warm the inside of the vehicle.

ANSWER : Depending on the particulars, you might have a warranty claim with Firestone. Obviously, to keep the cost down, be sure to exhaust that possibility first. If the check engine light is on, that is actually "helpful" as it means that trouble codes have been stored in the engine computer and those codes will provide important clues during the required engine diagnostic. If you request a check engine light diagnostic a certified mechanic from YourMechanic would use a code scanner to retrieve the diagnostic trouble code(s) from your car’s PCM (that is, the specific codes have caused the light to set) and then test the appropriate individual vehicle components or sub-systems (often a sensor, circuit, and the like) to pinpoint the reason why the check engine light has illuminated. Once the faulty part or component is identified, it is explained to your satisfaction and the mechanic will let you know of the cost to repair. If the resolution of the trouble codes does not resolve the stalling and rough idling, additional diagnostics are performed using a scan tool. The bottom line is if you schedule the recommended check engine light diagnostic, the mechanic will resolve this promptly for you and all on a mobile basis right at your location. If you have further questions or concerns as you decide what to do, do not hesitate to re-contact YourMechanic because we want you to make the most of your repair dollars and help you get the best possible results.