car seemingly overheats while idling. Help!?
May 21, 2006 1:24 AM   Subscribe

My car's engine heat indicator suddenly began soaring anytime I idle. This can't be good. What is the cause, and how do I fix?

Facts (some may be irrelevant):

1. Newer model car (05 Hynudai Sonata)
2. 5 days ago, the car seemed to reset itself (signs: clock reset, AC now celcius, back to drive-learning mode)
3. I never disconnected the battery in that time.
4. On cold start, engine heat indicator doesn't move at all.
5. On warm start, indicator continues up very slowly while driving (stops about 1/2)
6. In idle, continues up into red.
posted by donmayo to Travel & Transportation (12 answers total)
Likely that the cooling fan in front of your radiator isn't working. It could be simply unplugged, (though not likely) and it's easily inspected. When your car is idling, open the hood and look at the fan (or even listen for it with all other accessories turned off). If it is not running and your car is heating up, you've found the source of the problem.

Because of the other symptoms you descrive, it's probably related to the onboard computer. You should definitely have it professionaly checked.
posted by fake at 1:54 AM on May 21, 2006

fake is right, it sounds like the cooling fan is the most obvious cuprit. However, the cooling fan might not run all the time. In my car there's a thermostatic switch that only turns the fan on when the engine is getting pretty hot (just before the temp gauge reaches red).

If it almost reaches red on the gauge but then the fan kicks in and brings the temperature back down then it could just be working as expected
posted by amcewen at 2:09 AM on May 21, 2006

It sounds like you are having some basic problems in the charging or electrical system; quite possibly, your battery is bad, or connections to the battery are failing. Such problems often show up at the start of summer season, when higher under hood temperatures cause cracked battery cases to expand and leak acid fumes and fluid. If your electrical system is bad, your engine management computer, instrument panel, and engine accessory functions can all be haywire. To get this checked, you need equipment which can put a test load on your electrical system capable of handling a few hundred amps of electrical current. This is something most auto parts places or service shops selling batteries can do, sometimes for free or for a fairly low diagnostic fee ($20 -$30). Have it checked as soon as you can, since driving the car with a shorted or seriously defective battery can damage the alternator, the engine management computer, or other parts of the electrical system. It's possible that you may already have incurred alternator damage, as well, and the same test of your charging system that checks your battery should also test your alternator's ability to recharge the battery properly.

Once the charging system is known to be working properly, you should check the coolant level in the engine coolant overflow tank, and if low or discolored, correct the level or the problem producing the discoloration. A car shouldn't "use" any coolant, but if you have a very small leak, it may be hard to see on the ground under the car. You can put a clean piece of cardboard under the car overnight if you suspect a small coolant leak. Also, check the operation of the fan as noted above by fake, and the condition of the engine accessory belts, the water pump, and the hoses to and from the radiator and interior heater core.
posted by paulsc at 2:18 AM on May 21, 2006

The cooling fan probably does not run until the engine is warm. If you cold-start the engine, then open the hood to check the fan, you probably won't learn anything. Warm the engine thoroughly first. If the fan doesn't run even when the gauge indicates high heat, that's at least part of the problem. Check the fan connections.

Your 4) and 5) make it sound like an indicator or computer problem. In 4), are you saying it never indicates any change, no matter how long you drive? That's not (just) the fan; it should eventually indicate heat, unless the water thermostat is stuck open.
posted by Kirth Gerson at 2:40 AM on May 21, 2006

"How do I fix it?"

Seriously, sell the Hyundai. It is only going to get worse and worse. Consumer Reports list them as absolutely execrable in the reliability category. I knew someone who had a KIA (same car company who makes Hyundai) who went through 5 transmissions before making to 100,000 miles. I don't understand why anyone buys them.
posted by 517 at 8:25 AM on May 21, 2006

Consumer Reports list them as absolutely execrable in the reliability category. I knew someone who had a KIA (same car company who makes Hyundai)

This is wrong. Consumer Reports has rated Hyundai's reliability high for some time, tied with Honda at #2 below Toyota, and the 2005 Sonata was #1 that year. Hyundai did purchase Kia in 1998 (which means that a 100,000-mile car was probably before the purchase anyhow), but that's a business arrangement; Hyundais aren't rebadged Kias, but Hyundai is a giant Korean megacorporation.

But generally, cars are big, complex things, and individual bits of them sometimes break. The best manufacturers have a 10% problem rate and the worst a 25% so there's no-one manufacturing perfect cars. Selling them when one thing goes wrong is a good way to burn thousands of dollars, as silly as moving house because the furnace is making a weird noise. An '05 is under warranty. Just get the broken bits diagnosed and fixed at the dealer.
posted by mendel at 8:48 AM on May 21, 2006

You're under full bumper to bumper warranty right now. Not only will they fix it, they'll do it for free.
posted by SeizeTheDay at 8:55 AM on May 21, 2006

"This is wrong.."

Wow, so much has changed since I last went looking for a car. I'll shut up now.
posted by 517 at 9:29 AM on May 21, 2006

No one else has mentioned this... check the fuse for the radiator fan(s). The other related electrical problems you describe would make me check that. I'm not positive on this, but I see no reason why the engine computer should have anything to do with your cooling system; it has a lot more to do with emissions than anything else, and I'm pretty sure that a simple thermostat circuit is what triggers the fan to go on and off, not anything more complex. At any rate, your engine temperature should certainly NOT swing from hot to cool to hot to cool. It should warm to a static point and then remain there.

Generally, if the car gets hot while idling, and cooler while driving (air is then blowing through the radiator even if the fans aren't running), either your radiator is shot or the fans ain't working.
posted by autojack at 3:34 PM on May 21, 2006

Oh, also, said fuse may be under the hood, not inside the car. My Acura Integra has two sets of fuses, one in both places, and the radiator fan fuse is under the hood.
posted by autojack at 3:36 PM on May 21, 2006

A bit of a dumb suggestion, but check the water level in the radiator (not just the overflow reservoir). The same overheating happened to me with a 3/4 full radiator with the reservoir showing full. Went away when I filled it up with coolant.
posted by bystander at 8:55 PM on May 21, 2006

Not dumb. Smart. Same thought occurred to me, but I forgot to post it. Now that's dumb.
posted by Kirth Gerson at 12:22 PM on May 22, 2006

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