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Discussion Starter · #1 ·
I have been reading tons of thread but not finding what I'm working with.
2001 4 cyl. 5 speed w/ 248K Miles.

It started overheating at idle. After about 45 second or so the temp starts to climb. Turning on the heater or reving to 2500 will bring it back down.

First thing I check was fan clutch and it seem bad, I could stop it easily with cardboard with engine running and very hot. Spins easily while cold too.

I changed it out for a new one from autozone(not exactly the same, slightly larger and thinker but fits).

No change in performance, still overheating. Fan clutch is locked up when cold but slipping when hot. This doesn't seem right. opposite what is suppose to do. Is it bad out of the box you think?

Other things I checked. Coolant levels look good. Was flushed a 1.5 years ago along with new thermostat.

Opened radiator cap while cold. Ran engine, no water flowing till motor up to temp then water flowing through radiator.

I imagine I could use a new water pump and radiator but I don't really want to just through parts at it.

Any suggestions on what to do next? Thanks for reading and for any thoughts. Trying to keep this truck on the road without spending much on it.
 

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I had almost the exact same problem with my 07 that I never resolved. My total list of parts changed out was... radiator, fan clutch, thermostat and water pump. I also tried running an additional electric fan. It would be fine in colder weather of course but in the FL heat it would start running hot at idle fairly quickly.

My final solution? A 2016 SV 4x4. (The 07 already had 185k of hard miles on it)
 

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Discussion Starter · #4 · (Edited)
Was a parts store thermostat used or an OEM?

You say the radiator was flushed, but, what does the inside of the radiator look like?
Part store thermostat.

From what I can see inside the radiator doesn't look too bad from what I can see. Some slight discoloration of the metal, but no crusty build up of anything.

My man confusion at the moment is the fan clutch. Should it be locked up if the engine is hot/overheating at idle?
 

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Sounds like the fan clutch is working just as it should be. The stat seems to be working as it should be also by what you described. My guess would be either you have some blockage in the radiator that has fluid forced through it at higher RPM from the water pump or you have a water pump that has some fins failing that manage to move enough coolant when at higher RPM. I would also throw a new cap on that bad boy. They usually go bad as soon as you have one overheat.
 

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My man confusion at the moment is the fan clutch. Should it be locked up if the engine is hot/overheating at idle?
The fan clutch should be locked up/difficult to turn when it is hot/operating temperature.

When hot/operating temperature, spin the fan with your hand (tons safer if the engine is off !!!), fan should spin less than one revolution for sure. Can check Google for fan clutch troubleshooting.

Here in Arizona I've replaced fan clutches on my 1988 Mazda B2200 truck several times (Hayden lifetime warranty) and just once on my 1998 Frontier 4-cylinder, 5-speed like yours (but mine only has 210K miles).

On my Frontier, here are my only cooling issues: the radiator tank gasket leaked a little so got new radiator, and just replaced the fan then because it was cracked. Years later, I had a noise at higher rpm I couldn't track down, and I had a leak at water pump when its belt was off, and in that WP R&R discovered my fan clutch was always locked up (so cooling was OK, but extra noise and vibration). I installed a replacement fan clutch (lifetime, O'Reilly) and that took care of that, several years ago.
 

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Discussion Starter · #7 ·
Sounds like it would be a good idea to just do a cooling system overhaul. New water pump, radiator, hoses. I'm trying to be cheap though and I don't like throwing parts not knowing for sure the issue.

Also, should note that it has not "overheated" as in boiled over, steam, whatnot. Just gotten hot, like almost to the top of the gauge hot.
 

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Anything over normal operating temperatures is an "overheat" situation and can cause the radiator (pressure holding) cap to fail, especially older ones. I am assuming that you are probably still running the original cap from 2001. These are rather cheap and your issue may be as simple as the system does not hold enough pressure to move the fluid unless you are running at higher RPM's. I would throw a new cap on there and see if that resolves the issue.

There are tests you can have done to see if the required flow rate is being achieved that will tell you if you have an issue with the Radiator or the pump, but those will likely cost you just as much as replacing the parts plus whatever you will need to replace after they tell you what the problem is. Cooling systems are fairly easy systems to diagnose issues with.

Of course we can throw a major wrench into this and start thinking about a bad head gasket that is allowing hot exhaust gas into the cooling system and heating it up until you can get some additional airflow over the radiator.
 

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Discussion Starter · #9 ·
Thanks for the info. I will grab a new cap to see if that helps things as I'm sure the one on it is 16 years old now.

You are scaring me with that head gasket talk, but I guess motors can't last forever.

One more thing I checked earlier today is that the top hose going into radiator is very hot and bottom one is substantially cooler. Maybe radiator blockage.

I will have some more time to dig into it this weekend. Of course this had to happen on the one weekend it is over 100 in Portland, Oregon.
 

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Discussion Starter · #10 ·
Anything over normal operating temperatures is an "overheat" situation and can cause the radiator (pressure holding) cap to fail, especially older ones. I am assuming that you are probably still running the original cap from 2001. These are rather cheap and your issue may be as simple as the system does not hold enough pressure to move the fluid unless you are running at higher RPM's. I would throw a new cap on there and see if that resolves the issue.
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You win! Grabed a new cap for $8 and through it on this morning. All seems to be well and it has been idling for 10 minutes with ac on and it's 98 degrees outside. Temp gauge holding steady right where it should. Thanks all!
 

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You win! Grabed a new cap for $8 and through it on this morning. All seems to be well and it has been idling for 10 minutes with ac on and it's 98 degrees outside. Temp gauge holding steady right where it should. Thanks all!
Hey glad to see that it appears your issue is resolved. Sometimes the simplest things fix problems we think are huge deals.
 

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You win! Grabed a new cap for $8 and through it on this morning.
Grabbed ? threw ?

Or is there some type of voice thing that does the reply?
 
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