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Wanted to see if anyone else had this problem or might have a direction I can go to to help solve this issue...

Just a heads up, this problem has been going on since I bought the car 2 years ago, only happens in the summer when it's real hot outside, and only at, or near, idle with the a/c on. Long stop and go's, on the interstate during rush hour are a good example too. Car over heats while a/c is on, cools off when I turn it off, then over heats again if I turn it back on. Works like a champ while driving at a steady speed, it's just when it's idle, or near it, for about 5-10 min periods.

* Thought about the thermostat, but the engine never overheats unless the a/c is on, so that suggests that it's at least opening like it should to maintain temp.

* Both fans run. The belt driven on the engine, and the one on the front side next to the grill.

* Changed the timing belt a few weeks back so I changed the water pump at the same time. That didn't help it, still over heats. Changed all the hoses during this as well.

* While draining the radiator to get to the timing belt, it drained fast, and it filled up good. No hesitation like the fluid was hitting any blockage. No chunks or debris fell out during the drainage so no indication of sediment in the system.

The only thing that was suggested to me recently was maybe the clutch on the compressor might be putting too much strain on the engine and would possibly need some oil in the system to help lubricate it.

Seeing as how I would like to minimize the overall cost in trying to find a reliable resolution, I thought I would at least probe for more advice on hints to what I can check before spending money on something that may, or may not, work.

Any help would be appreciated, and thanks in advance for those who do provide input.

2,285 Posts
Wanted to see if anyone else had this problem or might have a direction I can go to to help solve this issue...

Just a heads up, this problem has been going on since I bought the car 2 years ago, only happens in the summer when it's real hot outside, and only at, or near, idle with the a/c on. ..
It sounds like it's either inadequate airflow, or inadequate heat transfer, so (if it was me), I would:

1) Physically inspect the condition of the fins on the A/C Condenser and Radiator - are there a lot of fins bent / restricting airflow between the (2) units?

If yes -

* DO NOT CLEAN before the start of this test. You want to measure the (existing) percentage of airflow being blocked..

I would measure the length / width of each unit and multiply to come up with the (total) area for cooling,

then measure the length / width of (each) area on each unit that have bent fins restricting airflow (multiply length / width of each area),

add all restricted areas together for a given unit, then divide by the total area to see what percentage of airflow is being blocked / restricted.

** You will have to pull the radiator to inspect (both) sides of the radiator and A/C condenser units to do this test. Check in bright sunlight and/or use a light on the opposite side of the A/C condenser so you can observe all fins on each unit. **


If the A/C condenser or radiator fins are being blocked by bugs/dirt/debris, now it's time to clean: Use an air compressor with an air nozzle, or a garden hose with a pressure nozzle from the (reverse) side of each to push out the debris towards the front of the A/C condenser & radiator.

using a soft pick tool, unbend any/all fins possible to open up the airflow path from front to back of each unit.

* If you need to use a metal tool, suggest purchasing a mini-pick tool set and using only at the fin edges to separate, then use a plastic tool to complete whenever possible..

Now re-calculate the percentage of airflow for each unit again.


2) The A/C condenser, radiator, and radiator shroud should pull airflow through the entire assembly as (1) continuous unit:

there should be a foam gasket surrounding the perimeter / sealing airflow between the A/C condenser & radiator, and a foam gasket surrounding the edge of the radiator shroud.

What is the condition of the foam insulator gasket (between) the A/C condenser and Radiator - is there a tight seal between the (2) units, preventing loss of airflow?

What is the condition of the foam insulator gasket surrounding the radiator shroud? Is there a tight seal, preventing air being pulled in from the engine compartment?

** Illegal air entering between the A/C condensor & radiator, and/or around the perimeter of the radiator shroud will dramatically reduce airflow that should be pulled through the A/C condenser and radiator.

Purchase some replacement soft foam (compressible) gasket material, clean and re-gasket each as needed.

3) Is the Radiator clutch fan fully engaging at operating temperature?

Using heavy gloves and long-sleeve shirt/sweatshirt for adequate arm protection, start the Sporty and run to normal operating temperature.

With engine off, key out, reach in and try to move the plastic fan blades on the assembly. The fan blades should be -tight- with a lot of resistance, the fan clutch should be fully engaged, the belt running to the fan clutch pulley should not move.

* Any deviation from the above should be inspected, addressed, and repaired.

Inadequate heat transfer:

4) Does the radiator have sufficient flow?

With the system drained of all coolant, top hose off the radiator, radiator cap on, and drain plug closed, cover the bottom radiator opening and fill with water through the top hose opening. Release and gauge the flow rate of the water. It should be a steady, strong flow rate.

5) Does the radiator contain an insulating coat (calcium or glycol buildup) internally?

With all hoses & radiator cap off, allow the internal radiator chamber to dry.

When dry, is there any apparent coating or glazing along the top coolant passage support?

Any apparent material obstructing the openings to the coolant passages?

If yes, then the cooling system should be flushed with a non-acid based product to remove any internal calcium or glycol (slime) buildup, such as:

Radiator 10 Minute Flush (p/n 1211) | Products | Bar's Leaks & Rislone - Premium Automotive Chemicals

a 12 ounce bottle is sufficient for the Sporty's cooling system.

* See the manufacturer's website for proper procedure and precautions in using the product.

IMPORTANT: If you have well water, only use either distilled water, or (chlorinated) city water for the flush / and clean!

Well water contains too many minerals to use for this procedure, and will reduce the effectiveness of the flush product.

City (chlorinated) tap water actually works well, the chlorine in the water aids in the cleaning action.

* After flushing the system using the product, refill with water only, and run another 5-10 minutes, to remove any remaining product / residue from the system.

IMPORTANT: When flushing / cleaning, DO NOT drive the Sporty, the flush and clean procedures should be done with vehicle stopped.

When flushing / cleaning, you should be -closely monitoring- the dash coolant temp. gauge, and using a SECOND / EXTERNAL thermometer, such as an IR thermometer to monitor temp at the base of the thermostat housing (where the top radiator hose connects) ..

6) What is the condition of the radiator pressure cap and overflow tank assembly (tank, cap, hoses) ?

When the coolant is heated, it expands -> builds up pressure in the cooling system.

The radiator pressure cap is designed to open at a specific pressure and allow hot coolant to flow -> into the overflow tank.

After the motor is shut off, the radiator / system draws the coolant back into <- the radiator from the overflow tank.

Remove and inspect the radiator -> overflow tank cap supply line (hose), it should be free of obstruction, with no splits or cracking visible.

** When fitted onto the radiator overflow outlet, and onto the tank cap inlet, each connection should be tightly secured to prevent air from entering the system.

IMPORTANT: this hose should not have any coolant visible around the radiator connection or overflow tank cap connection - if you find -any- coolant present in any amount, treat the hose as suspect and either replace, or if the hose is in apparent good condition, add some spring clamps to both sides of the hose!

Remove the overflow tank cap and inspect the overflow cap -> tank supply hose, it should be free of obstruction, and of sufficient length to reach to the bottom of the tank.

** When fitted onto the tank cap, it should be tightly secured to prevent air from entering the system. THIS IS A COMMON FAILURE POINT, and will draw air into the cooling system -> cause overheat.

Physically inspect the interior & bottom of the overflow tank. Any debris, slime, or scaling visible?

** If so, the tank should be thoroughly scrubbed, flushed out with water, then drained / blown out with compressed air to remove any particulates that may be drawn back into the cooling system.

The (air inlet / overflow drain) hose on the overflow tank cap should be removed, inspected, free of any obstruction or debris, and when installed, routed alongside the tank -> facing down.

7) What is the age / condition of the coolant?

The coolant should be a 50/50 mix of antifreeze and -distilled water- only: either purchased pre-mixed, or if you mix, again with -distilled water- only.

The vehicle should be (cold) when filling, drain plug closed, all hoses in-place and secure,

the coolant should be filled from the top radiator cap opening up to the top of the radiator,

the overflow tank should have fresh coolant added to it, the coolant should reach the (low) mark of the overflow tank, the

the top radiator hose should be squeezed (or "burped") to push out any trapped air in the hose / system, twice (2x),

at engine cold, and engine hot / at operating temp., using heavy gloves from above.

After everything is back together, - the system should be closely monitored:

*** monitoring the level of coolant in the overflow tank is the quickest indicator of any issues with the system: the coolant level should remain at the (low) mark of the overflow tank, and rise to the (high) mark:

The level of coolant in the overflow tank should be inspected regularly during the summer months, frequently, if you suspect any cooling system issues.

In short, all the above is basically rehabbing -> Q/A'ing the cooling system back to (original) factory condition.

If you inherited a cooling system issue, it is important to take the time & do the work to inspect and repair it back to working order.

As you inspect and either repair or certify as good each part of the system, you are closer to narrowing down & locating the source of the issue.

re: A/C clutch compressor causing issue: unlikely, but -all- moving components should be inspected: belts should be in good service with no glazing or fraying, all components (A/C clutch & Idle pulley, Power Steering pulley, Alternator Pulley, Fan Clutch pulley) should turn freely with minimal resistance / no binding / no excessive noise..

... I suspect your issue is airflow related, given that the overheat only occurs at idle, with A/C operating, but it is important to -fully- Q/A the system with the steps above, doubly important to ensure no air is entering the cooling system.


2 Posts
overheating while ac on at idle problem fixed

hi i am new at this forum i have a 2000 kia sportage and i had the same problem i replaced the fan clutch and now is working perfect
you can get the fan clutch from ebay and is really easy to replace it
hoope that helps :cool:
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