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robaincltnc 04-26-2003 12:28 AM

Running Hot
Hey folks,
My 4 Runner appears to be running hot. I had it out in traffic tonight and when idling or stop and go the temp guage went to the red. Its never done that before. I know that this is a MB site but thought this kind of scenario would be widespread enough to cover Japanese. Is is the thermostat?
Thanks for you help!
rob, charlotte

drbrandini 04-26-2003 01:27 AM

Thermostat is your best bet! Also check your coolant level and makes sure you have enought and the correct mixture of water and anti-freeze. Too much anti-freeze is not good.

robaincltnc 04-26-2003 08:44 AM

Thanks more thing..

When I got the car home I let it idle with the AC on and the temp was it appears to be an intermittant problem..does this help with diagnosis anyone?

NormanB 04-26-2003 05:15 PM


Not familiar with your car BUT if you have an intermittent overheating problem it could be a dodgy thermostat or it could be the cooling fan system (if it is electrically driven and activated by thermosensor).


robaincltnc 04-26-2003 06:02 PM

It turned out to be very very low on antilfreeze. I added about a gallon and it appears to be fine. The radiator is less than 3 years old, and I had it flushed less than a year ago. Where did the antifreeze go? The oil isn't cloudy and I haven't noticed any leaking anwhere.

Thanks again for the replies!

chicago124 04-26-2003 08:49 PM


Well, it's time to pressure test the system.

You have a leak that may be near the water pump or leaking near a very hot part of the engine and therefore the coolant is steaming off and draining on the ground. Another possibility is a head gasket leak.


Jason Beal 04-27-2003 01:03 AM

Be sure to track down where the coolant is going. It's gotta be going somewhere if you are loosing alot. Pull a spark plug and see if it's extra cleaned (ie steam cleaned). Maybe do a compression test too. Test or just replace the radiator/pressure cap. If the pressure is too low the water pump won't put out the correct flow (somebody correct me if I'm wrong). I just did a headgasket job on a Honda CRX that heated up real slow in stop and go traffic. The tear was small, but enough to overheat it. The head wasn't warped though, lucky for me. Good luck.

robaincltnc 04-27-2003 01:14 AM

Chicago:So what are other signs off head gasket leak? I know (or think I know) that I have a valve cover gasket leak. I can see a small ooze and can smell the oil burning). I have noticed that the car uses much oil. It probably uses 2 quarts between oil changes. My dealer at one point said the rear main seal was leaking but when I said that I have never ever seen a bit of oil drop on my concrete he was sort of flustered...I have not seen the smallest of a leak. I think that he just wanted the job. As far as the head gasket, how do I know if its leaking..would I notice the antifreeze dripping underneath the car? If their is a leak in the system, would this at all be a faulty radiator? The radiator has a lifetime warranty.

tkamaya: last time the coolant was checked was when I had the radiator flusher..maybe 6 months ago. Today I filled the radiator with antifreeze and filled the resevoir, so I should be able to notice if it goes down.

Thanks again.

jsmith 04-27-2003 10:40 AM

be sure to purge your cooling system of any trapped air. that will account for uneven temps. do a search on the toyota newsgroups and you will find the correct procedure.

if your toyota has the long block six they are notorious for blown head gaskets although i don't know to what year. if you have clouds of white smoke coming from your exhaust that's a sure sign.

chicago124 04-27-2003 11:16 AM

Hi robaincltnc,

You may never see coolant actually leaking. It may never appear under the car.

Try this, get some coolant leak tracing fluid. NAPA of another parts store will have it. Just tell them you want to trace a coolant leak. You'll need a black light as well. Follow the instructions.

After running the car for a while, shine the black light in (at night helps) and you'll see if there is a coolant leak.

My 300E's head gasket started leaking badly and there was little white smoke. Pulling the plugs confirmed the problem. A very wet spark plug in the front cylinder told all I needed to know. If one of yours is unusually clean, that's a good sign something is up. Mine actually hydrolocked the motor (while it was sitting overnight) and that was a sure sign:-) Water shot out of the cylinder after removing the plugs and then cranking the motor. Fortunately, the head is okay and the bottom end is fine.

Net result, getting a valve job since the head is coming off.

Good luck,

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