AllBlackTibby

I need help from y'all. I know it's an Elantra, but it's very similar to a Tib, and I know this is where all of the smart people hang wink1.gif I'm not up to snuff with a modern day engine, so pardon my ignorance.

Yesterday, on a cool day (temp was in the 50's), my wife was driving her 01 Elantra and it began to quickly overheat on her.
I'm trying to narrow it down as there's not really a lot that can cause a car to overheat.
The only things I can think of are:

Coolant level (which was fine, no leaks)
Thermostat
Fan not kicking on
Water pump failure
Blown Head Gasket (which it's not).
Maybe an air bubble in the system?

Anyhow, if the thermostat was stuck closed, it's my understanding that hot air would not blow out of the vents if you kicked the heater on? Is this correct?
I made her kick the defrost on high, when she did the temp immediately started to come down, like in a matter of a few seconds (BTW, hot air was coming out of the vents). My guess is that the fans weren't coming on and kicking the defroster on made them come on. So there's a switch or sensor somewhere that tells it to do this, correct?

I've got a newborn baby, and I haven't been able to do much else other than check the coolant level and talk over what happened with my wife. I haven't had a chance to even duplicate the problem yet.

So, with all that said, should I be focusing on fuses/relays? Where' is the relay/sensor that tells the fans to kick on once it reaches a certain temps? What other steps should I take to narrow my problem down?

I appreciate any help in advance.

Ericy321

You pretty much got it in order of what to check out. Turning the defroster on should kick on the ac compressor which would turn on the AC fan. Now what I would do is let the car run and get up to temp and see if the main fan kicks on when it reaches temp. If it doesnt, go after that. Changing the thermostat wouldnt hurt either.

radu_rd2

I'm not sure if that's correct, but I would think that if the thermostat was stuck closed then at least the radiator itself won't be hot. Also, when you're overheating, excess coolant should flow to the overflow tank and you would see it 'boil'. If that doesn't happen, the thermostat is probably the problem.

But I doubt it's your thermostat really, since turning up the AC fan cooled her down.

I would first do what ericy said above to check if the driver's side fan starts spinning when the temp goes up to operating temperature, that could very well be your issue and a fairly easy fix. I'd also check if there isn't way too much grime on the radiator, you can take off the top mounts and pop it out rather easily to take a look (without disconnecting any hoses or draining coolant)

AllBlackTibby

Yeah, now that I think of it, the thermostat stuck closed wouldn't matter. Someone told me that, and I just assumed they knew something.
If you think about it, your car starts blowing hot air out of the vents well before the thermostat opens, and the fact that kicking on the AC instantly cooled it down kind of eliminates that.

I didn't want to rule it out because I didn't think a car would heat up so fast on a cool day if the thermostat was working right.....but apparently I don't know that much.

Stocker

The thermostat is an easy DIY check, if you don't mind spilling some coolant. Pull it out and drop it in a pot of water on the stove. Put a thermometer in the water and watch as the temperature of the water increases. If it opens properly, you're done. If not, they are cheap.

They can also half-open, stick (intermittent overheating) or be cracked.

AllBlackTibby

Well, I got off work early and got a chance to do some trouble shooting.
Survey says: Thermostat.

The upper radiator hose was nice and hot. The bottom one is extremely cold, not even warm to touch. The fans were running away, both of them.
Turning the heat on did help, my only guess is that it was helping burn off heat from the engine.

So, I'll be replacing the thermostat on it.

radu_rd2

If the upper hose was hot, doesn't that mean that the thermostat works? Thermostat is on the side of the engine block..

Did it overheat again? And turning on the heat helped?

AllBlackTibby

That's what I thought too. I confirmed my issued today. I replaced the thermostat. It had snapped in two and a portion of it was blocking the hole for the lower hose.

Not bad. I've had the car 8 years and this is the first mechanical issue its had.

Anyhow, runs great now. I've put about 25 miles on it now, still running normal.

Thanks for the help.

radu_rd2

Oh, interesting, glad you fixed it!

Stocker

That's the third Hyundai Beta with a broken thermostat that I've read about. Well, I'm glad you've got yours going again.