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Old 07-27-2015, 08:14 PM
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1999 gc laredo over heat

I still have ( for now at least) my green 1999 grand cherokee Laredo 4x4. His name is Shrek.
I recently fixed an o2 sensor problem thanks to fango, and now a new problem pops up.
It over heats while at slow speeds or stand still.
Radiator new and re-tested, thermostat new, upper and lower hoses new ( that is a whole different story for another time), radiator cap new, water pump no noise/looseness/leakage.
Only thing left is the cooling fan and controller.
Using a scan tool with live data, I can see that the cooling fan does come on, but not until temp hits 211 ish. It is my understanding that the fan should be coming on initially at 195-200, then getting faster if needed. It also doesn't seem to me that it is running as fast as it should when it DOES finally come on, and it certainly isn't cooling the motor effectively.
When i wire fan directly to battery, it spins much faster.
When i disconnected the fan after it has kicked on, and checked voltage at plug, it shows 12.5 volts.
If i were to check voltage at lower temp, like say 195-200, should there be voltage but lower?

And thoughts would be helpful. I am getting pretty frustrates. This is my daily driver, and i am constantly sweating the drive to and from work hoping to make it without too many stops.



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  #2  
Old 07-27-2015, 08:14 PM
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Re: 1999 gc laredo over heat

Oh, it has the 4.0 not the 4.7



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Old 07-27-2015, 08:52 PM
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Re: 1999 gc laredo over heat

If this is helpful information, I drove it for a couple of days without t-stat (out of sheer necessity), and at highway speeds, temp stayed at about 147.


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Old 07-28-2015, 11:56 AM
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Re: 1999 gc laredo over heat

I can be wrong, but i believe that the fan is suppost to come on at 210F. At 190 the T-stat begins to open and coolant starts to flow through the radiator. To me the system seems to be working normally.
When removing the T-stat, the coolant temperature will be (too) low when driving on the highwah, since all coolant passes through the radiator at all times and will be cooled down with lots of airflow.
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Old 07-28-2015, 01:08 PM
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Re: 1999 gc laredo over heat

After more research, i know this to be correct. However the fan is not spinning out fast enough to actually cool system.



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Old 07-28-2015, 01:12 PM
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Re: 1999 gc laredo over heat

Since i had everything apart anyway, and being tired of trying to trouble shoot, i went ahead and replaced fan motor, controller, and temp sending unit.
It is now operating like it should. I believe that the fan was beginning to fail, because it was not spinning fast enough to do anything. The other stuff was probably due to replace anyway with almost 210000 miles.



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Old 08-03-2015, 02:39 PM
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Re: 1999 gc laredo over heat

I too have a 1999 Jeep GC, the Loredo edition with the I6 4.0. I have read several accounts of them having issues with overheating and it is usually tied to the fan. From what I have read, 1999 was the first year that Jeep switched from a mechanical fan to an electric fan. The difference being that the mechanical fan is controlled by the serpentine belt and the electric fan is controlled by the computer.
It is my understanding that if you find a 1998 Jeep GC at a junk yard, you can swap the mechanical fan from it with the electric fan in your 1999 and solve the problem. Google about it and you will see several mentions of this switch.
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Old 08-26-2015, 05:39 AM
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Re: 1999 gc laredo over heat

Last night, i reached out to powerstop. It occurred to me that when I was doing the install, i had to move the bleeder nipple to the other hole because i could not have been able to connect the brake line the way it was configured. The holes were the same size, so I didn't figure that it would have made a difference but it might.
Lets see what they say.


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Old 08-27-2015, 12:03 AM
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Re: 1999 gc laredo over heat

Powerstop is sending out a new caliper.
They feel that it might be defective.


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Old 08-27-2015, 07:39 AM
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Re: 1999 gc laredo over heat

Seems that you are answering in the wrong thread, you probably have too many problems with your jeep to keep the things separated.
Just kidding. Didn´t you have the dragging brake with the original caliper as well?
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Old 08-27-2015, 10:05 AM
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Re: 1999 gc laredo over heat

You are correct about the multiple issues.
And a brake issue was there that was causing rotors to warp. I am not sure what the original issue was. Sometimes fauly new parts can confuse what and where the whole problem started


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Old 08-27-2015, 10:06 AM
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Re: 1999 gc laredo over heat

And clearly, i didnt have my glasses on when i picked which thread to reply to.


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