Engine running hot-mystery

sawzall · 08-16-2006, 12:39 PM

My 01 Optima starting running hot about 6 weeks ago.
Symptoms: In the coolest part of the day, the morning, it will run fine on the freeway until I come to several stop lights. Then it starts creeping up to the red unless I kill the AC and crank the heater on full blast.
During the hottest part of the day, it barely rises above the middle marker, slightly warmer then normal.
I've verified both fans are working as advertised.
The coolant in the radiator hasn't dropped at all, although I have added maybe a quart/week into the reservoir.
Radiator cap has been replaced.
Thermostat has been replaced (genuine KIA). No changes in symptoms.
I'm thinking at this point I have a bum coolant temp sensor or clogged radiator.
Having the AC on/off definitely increases/reduces the heat load and is apparent on the temp gauge when it decides to start running hot.

Any ideas? I don't believe my system has ever been flushed and I have 89K miles on the clock. The coolant appears normal, no rusty or non-green color.

ALSO, does ANYONE KNOW WHERE THE DRAIN PLUG IS ON THIS RADIATOR? Kia's techinfo doesn't indicate it.

My cooling system is obviously not able to dissipate enough heat and of course this is happening in the summer and I'm in PHX. When the temp was over 110, it overheated much more frequently natch. However, this is the first time it started to overheat in the last 4 summers

thanks!

sawzall · 04-17-2007, 09:13 AM

Bump!

This is still a problem for me. I've drained the coolant and replaced but didn't flush as the supply/return hoses are buried by the firewall. The coolant looked fine.
I've replaced the rad cap and thermo as well and I still get the random spike in temp forcing me to crank the heater on full blast to bring it down. Any ideas?
So far the symptoms are only showing when I'm slowing down or idling after running so I'll have to verify the fans are kicking on. Last summer, it would happen even while driving 75MPH but again, it was intermittent.
Any help would be appreciated. Thanks!

Forgot to ask, could this be a weird sensor issue?

ron1004 · 04-17-2007, 09:31 AM

If your coolant has never degraded such as signs of corrosion, then I'd rule out water pump and pluggage of the water passages in the rad.

In my humble opinion it sounds like a cooling air flow problem - check the fans, and make sure there's no spider webs obstructing the air flow through the radiator.

Psychlopath · 04-17-2007, 08:40 PM

Have a dealer check it would be a good place to start.

On my stupid Optima, it will show overheat all the time. Mostly randomly.

If I turn the key off then back on, the gauge is back to "normal." the dealer supposedly has changed the thermostat, sending unit and gauge.

I find that to be a lie, since there's nothing left to cause the problem if, as stated, the computer indicates there's never been an over heat.

Either way, it's more stupidity on the part of Kia's horrible customer service.

The dealer (or any mechanic) can read the computer to see if it has ever recorded an over heat...if it hasnt, youre getting a false reading some how.

KodaTech · 04-18-2007, 10:05 PM

if it runs fine on the highway, and overheats in traffic, i would say the radiator fan(s) are not working. they dont come on over say...30mph because airflow does it for them. check the fans.

ekubec · 04-19-2007, 12:26 PM

Having to add a quart per week to the resevoir, is NOT normal. I have never had to add any coolant to the resevoir.

So somewhere there is a leak.

ron1004 · 04-19-2007, 01:03 PM

Quote:

Originally Posted by ekubec

Having to add a quart per week to the resevoir, is NOT normal. I have never had to add any coolant to the resevoir.

So somewhere there is a leak.

That is a point of note!

You are needing to top-up the coolant an abnormal amount, which could be a leak, or boiling which is expelling coolant.

Daytonabob · 04-25-2007, 08:09 AM

Two things you need to check...1. Check the top and bottom hose to see if one or both are getting flat instead of round. That will restrict the flow of coolant. Solution is to replace the one or both causing the problem. 2. Check the transmission fluid to see if it is still red or has turned black, that too will cause the radiator to overheat. Suggest you find the solution fast, you stand the chance of blowing the heater core and you don't want that to happen...

sawzall · 04-25-2007, 11:55 AM

Well, I just checked the fans. I drove about 40 minutes in city traffic and noticed the temp gauge climbing a bit past the half way mark after I came to a stop for a minute or two at a light.
AC was not turned on for the drive, I checked the fans and neither were running after I got to work and left it in Park.
So, I guess the next question is, what would be the likely causes of the fan not running with a 2001 Optima? I'll start checking wiring and testing this weekend. Could it be a bad ground wire? Bad fan motor?

Thanks again to all for your input. Its been almost a year but I'm pretty sure the fans were running when I checked them. Today the one that should have been running was not. I'm not sure which one it is of the two (radiator, not AC) either.

Psychlopath · 05-14-2007, 08:52 PM

It COULD be the fans, but probably not. Grounds are also unlikely, however you should still check them. Try looking at the fuse first. If that's good, it's likely the thermostatic switch that turns the fans on and off. If you can let it idle 'till it begins to over heat (dont let that thing boil over!) then put a multimeter or test light on the switch, you can check it pretty easy.

If you really wanna get into checking the fans, you can hot wire them to the battery and see if they come on. If they do, it's not bad fans.