Intermittent overheating

G

Grom

New member
I have a 2004 V6 4runner with about 145k miles that is a daily driver for my wife. Since the weather has got hotter and hotter this summer, I have noticed that some times the car would overheat, at low speeds (city driving) or at idle.

After temperature gauge start to move to high, it cools to normal again. This makes me nervous as I believe that this variation of temperature is not normal.
When moving, the variation is minimal. When at idle, it can get a lot hotter before the fan cools the engine back to normal levels (middle of temp gauge).

I am not sure where to start, I first thought the thermostat might be misbehaving and not working properly.

Then I was thinking that the clutch of the fan may be the issue.

Finally I am thinking that the radiator may need to be replaced.

Is there a way to figure out which might be the culprit? Or are there any other possible scenarios?

Thanks!
 
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riceandpho said:
whens the last time the coolant had been service? usually a drain and fill, but u might need to flush.
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I am not sure but the coolant, at least in the expansion tank looks new. She takes the car to the dealer since before we met and I assume they flush the coolant as necessary (or even more often than necessary).

I'll check the coolant in the radiator. Assuming the coolant was flushed recently is there anything else to check?
 
Hmmm... So, it overheats sporadically/randomly? I would probably check the thermostat as when they start to go bad, they will sometimes open and close randomly. Yup, that's where I would start. Just my 2 cents.
 
preacher35 said:
Hmmm... So, it overheats sporadically/randomly? I would probably check the thermostat as when they start to go bad, they will sometimes open and close randomly. Yup, that's where I would start. Just my 2 cents.
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The thermostat doesn't turn on and off randomly, I think. The issue is only during low speed of stuck in traffic. At high speeds temp is steady.
preacher35 said:
Oh, and where in Houston are you? Friendswood here.
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West Houston/Katy here!
 
I had a Camry that I decided to have the engine rebuilt in. After a few months it started to get warm every now and then. Basically at highway speeds it would stay normal then say I came to a red light from 70 to 0. It would immediately start to warm up over normal. Radiator, water pump, and thermostat was replaced with rebuild. Swapped the thermostat and it returned to normal :)
 
There could be air in the system, perhaps it was recently serviced when she brought it to the dealer and there is an air bubble in the cooling system. It may need to be 'burped".
 
Thanks,
I'll start with the simplest/cheapest option and try to burp the system before start replacing stuff. Thermostat might be the first to be replaced.
 
TheeMikeB said:
There could be air in the system, perhaps it was recently serviced when she brought it to the dealer and there is an air bubble in the cooling system. It may need to be 'burped".
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I needed to be burped! I drove by the dealer and picked up a bottle of Toyota coolant to avoid mixing different types/colors and potentially creating sludge.
Thanks again everybody!
 
Only because of similar issue on my is300 , did all the above new rad , water pump , therm, it would only happen in long waits in drive thru's & such , but it was the fan switch was not hooked up , needed to splice it back together , I think 4r have them ?
 
So I just created an account to research these same symptoms. 2004 4runner with 143k. Same symptoms, gets hot only after running it for 40+ mins and seems to be when stopped or stop/go, not steady highway speeds. Shop ran some chemical test and it passes when it's not overheating, but fails when they were able to get it to overheat again. Also said the coolant is bubbly. They are thinking blown head gasket, cracked cylinder or block. Thermostat hasn't been replaced and they don't think it's that at all. Suggested it may be time for me to research a new vehicle. Looks like I'll have to check this fan switch thing. I'm not opposed to replacing it, but if it's not major, I'd rather hold onto it and save the $$.
 
Can you see light thru the radiator or is it clogged? Clean it. Intermittent sounds like an air bubble. If its not the radiator, think head gasket. Take it in and get tested.
 
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