Why is my car's A/C causing my engine to overheat?

[spingears]

@Subway Prophet

I’m driving a 2004 Kia Optima. The outside daytime temperature has been in the low- to mid-100’s F this week, which I think is the hottest I’ve experienced. I’ve noticed my car’s engine temperature gauge will go into the red zone if I have my air conditioner on for more than a few minutes. If I turn off the A/C, the temperature gauge hovers at about mid-level.
Needless to say, I’ve learned to bring plenty of water for my 70-minute commute.
But I see plenty of people driving with their windows up, so I assume that their air conditioners are working fine despite the heat. What would cause my air conditioner to misbehave?

Mid-100’s F means 105 +/- ?
Commute means stop and go driving?
Stop & go with over 100 F ambient leads to engine cooling system running very hot due to lack of fast air movement over/thru the radiator and extral load on the engine cause by the a/c compressor.
Drive faster, stop less, or use 4-40 a/c!

[Gary_T]

@Subway Prophet

Thanks for the expert response.

I waited until my radiator cap was cool enough to touch, and popped it off. It appears that it’s full of coolant - the coolant was about level with the gasket. The spill tank is just slightly lower than the “HOT” line.

That sounds fine. We can eliminate low coolant as a cause. I think the most likely explanation is that the system is at its limits in this heat. Eliphalet raises a good point though - if something is blocking airflow through the condenser and radiator, they can’t perform properly. When you look through the grill, the condenser is what you see. It would be wise to verify that it’s not restricted as he described.

I couldn’t find a second radiator at the front of the car, though the radiator that is there is quite wide, and has two fans. Also, I think I’ve found the compressor, and it has tubes leading to the radiator, as does the water pump. Is it possible that the A/C radiator is incorporated into the main radiator?

No. I think it more likely that you’re not able to see the “dividing lines” between the two components. The condenser on your car is directly in front of the radiator.

The A/C compressor has one line that goes toward the firewall, to the accumulator or evaporator, and another that goes to the condenser. The other A/C line from the condenser goes to the firewall as well. These lines usually are of pipe-hose-pipe construction.

The radiator has one hose that goes (typically) to the water pump, and another that goes to somewhere on the upper half of the engine, usually to the thermostat.

[Subway_Prophet]

@Gary T

Eliphalet raises a good point though - if something is blocking airflow through the condenser and radiator, they can’t perform properly. When you look through the grill, the condenser is what you see. It would be wise to verify that it’s not restricted as he described.

Could I just take a garden hose to the area? Or are there parts under the hood that I don’t want water in? (Assuming that all the seals are good, etc.)

The A/C compressor has one line that goes toward the firewall, to the accumulator or evaporator, and another that goes to the condenser. The other A/C line from the condenser goes to the firewall as well. These lines usually are of pipe-hose-pipe construction.

The radiator has one hose that goes (typically) to the water pump, and another that goes to somewhere on the upper half of the engine, usually to the thermostat.

Ok, thanks! I’ll try to confirm this arrangement, and check for dirt and leaks and whatnot.

When I look for a leak on a gas pipe in the house, I use sudsy water. Will this trick work here?

[Subway_Prophet]

@spingears

Mid-100’s F means 105 +/- ?
Commute means stop and go driving?
Stop & go with over 100 F ambient leads to engine cooling system running very hot due to lack of fast air movement over/thru the radiator and extral load on the engine cause by the a/c compressor.

This is one of my primary suspicions, though I am still concerned that my engine is somehow broken and by running the A/C I may break it more.

Drive faster, stop less, or use 4-40 a/c!

Hee hee! I’m all for driving faster - though the row of big rigs ahead of me disapprove - and they’d certainly win the argument! As for stopping less, I’m the kind of driver that prefers a slow and steady 5 mph, rather than tailgating and alternating between 15 mph and 0. But it’s still pretty damn slow, especially when it’s 104 outside. And people will constantly cut you off to take that space in front of you when you’re not tailgating, to shave that .03 seconds of their own commute. :smack:

What’s 4-40 a/c?

[Gary_T]

@Subway Prophet

Could I just take a garden hose to the area? Or are there parts under the hood that I don’t want water in? (Assuming that all the seals are good, etc.)

It’s best to avoid spraying water (especially under pressure) on the engine and any electrical connectors or devices, so be careful. However, if there’s debris on the forward surface of the condenser, you can probably get a lot of it with a hose and pressure nozzle. Remember, this stuff got applied from the front, and to remove it you have to apply a stream from the rear - from inside the engine compartment aimed towards the front bumper.

When I look for a leak on a gas pipe in the house, I use sudsy water. Will this trick work here?

??? I’m sorry, I don’t understand why you’re asking this. The subject of findings leaks has not come up, and doesn’t apply.

What’s 4-40 a/c?

4 windows down, 40 mph.

[Gary_T]

Let me clarify: “…from inside the engine compartment through the radiator aimed towards the front bumper.”

[havasutimo]

@Subway_Prophet

I’m driving a 2004 Kia Optima. The outside daytime temperature has been in the low- to mid-100’s F this week, which I think is the hottest I’ve experienced. I’ve noticed my car’s engine temperature gauge will go into the red zone if I have my air conditioner on for more than a few minutes. If I turn off the A/C, the temperature gauge hovers at about mid-level.

Needless to say, I’ve learned to bring plenty of water for my 70-minute commute.

But I see plenty of people driving with their windows up, so I assume that their air conditioners are working fine despite the heat. What would cause my air conditioner to misbehave?

I have a 2003 Kia Optima that just developed the same problem. The air conditioning condenser coil is layered in front of the radiator. There is a gap between the two that is visible if you are looking straight down in front of the radiator.

I cleaned the condenser coil and radiator, and did pull out a lot of oil, dirt, and debris. But I also noticed that there are two radiator fans on this model. I suspect that one of the fans is not working properly. This may be a thermostat/relay issue, or a worn electric motor. I will check it during its next drive to confirm.

This is not an air conditioning issue, it is a cooling issue. If all belts and hoses are good, then that leaves only a few basic things to fix. Since it stays cool till the air goes on, I would suspect the secondary fan is not kicking in, since the cooling system works otherwise. Don’t be afraid to pop the hood and clean the condenser and radiator. Just remember to use a bug sprayer or lower pressure to clean with since high pressure systems have a tendency to bend fins. Fill your bug sprayer with dish soap and clean all the way to the bottom. I found that the bottom portion of mine was most clogged, and since the primary intake under the hood brings air in at this point, it made sense that this may be the problem.

If it were an air compressor problem, you should not be getting any cold air out when engaged. This can be tested at idle during warm up to confirm, before normal warmed operation. Simply turn on the air, and see if it blows cold. If it doesn’t, then get a can of refrigerant and fill it up. They now come with the gauge so you can see when it is full, and are quite easy to use, and relatively cheap. Check for leaks. It is cheaper to do this as a test before taking it in for service.

I will repost as soon as I test the car tomorrow. It should be about 120F, so this should be a good test for anywhere on the planet.