2002 Jeep Liberty Renegade (3.7 L) overheating with AC loss - JeepForum.com
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Unread 09-21-2013, 10:08 PM   #1
mjb2066
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2002 Jeep Liberty Renegade (3.7 L) overheating with AC loss

Hello,

I don't know much about cars and was hoping to get some tips, advice, or help from some of the members of this forum. Recently, the engine of my 2002 Jeep Liberty Renegade (3.7 L) has begun to overheat whenever I run into stop and go traffic. This occurs regardless of whether or not I have the AC running in the cabin. However, when I do have the AC running in the cabin, I notice that the engine overheating is accompanied by warmer / uncooled air coming out of the cabin vents. The engine temperature goes back to normal (just left of the middle of the gauge) and the AC starts working normally again, as soon as I'm able to maintain forward motion for the most part, even at surface road speeds (25-35 mph). Putting everything together, I assumed it was a problem with air flow over the condenser and radiator when not moving forward, and figured the electric radiator fan is only working intermittently. After doing some searching on various jeep forums, I decided to replace the radiator fan relay, as it was a cheap fix and seemed to have a long history of problems and design revisions. The problem persisted after changing the relay, so I began to suspect the electric radiator fan itself. Yesterday, I drove around for a while, pulled into my driveway, popped the hood, and let my engine idle. Shortly thereafter, I could feel the air coming out of the cabin vents warm and noticed the engine temperature climbing, but the fan never stopped working. Is it possible that the fan is still the problem (i.e. spinning too slow)? I have no way of knowing how fast it should spin and no way of knowing how to quantify how fast the fan is spinning. If it's not the fan, what else could be malfunctioning that would cause the car to overheat and a loss of AC when stopped for prolonged periods of time? Could it be the thermostat or the dual function high pressure switch? I though the AC compressor was acting a bit strange when I had the hood open yesterday and the engine began to overheat. It was kicking off and on quite frequently. I could see the clutch engaging and disengaging.

Anyway, any help would be greatly appreciated. For the last month, the only way I've been able to work around this issue is by avoiding traffic and running high heat in the cabin when the engine does overheat. The old girl has run faithfully for 140,000 miles, but I'm probably going to be getting a new vehicle soon, so I don't want to spend a lot of money on repairs, if possible. But at the same time, I don't want to pass my problem on to the next owner.

Thanks,

Matt

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Unread 09-22-2013, 05:25 AM   #2
tjkj2002
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Stop driving it,the 3.7 does not like repeated overheating as it tends to drop a valve seat and that is a expensive repair($2000+).


From your description sounds like the fan works so the only thing left is coolant flow,IE the water pump.
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Unread 09-22-2013, 08:13 AM   #3
streetglideok
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+1 on that. How is your coolant level, etc? If you have not kept up with maintenance on your vehicle, you have made the diagnosis more difficult. Coolant system neglect can lead to restrictions in the coolant system, or water pump issues. If you continue to abuse your vehicle by allowing it to overheat, you'll be left with a jeep and a bad engine, no if, ands or buts. And before the naysayers come in, most modern engines are intolerant to overheat issues.
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Unread 09-22-2013, 04:40 PM   #4
tjkj2002
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Quote:
Originally Posted by streetglideok View Post
And before the naysayers come in, most modern engines are intolerant to overheat issues.
+1 on that as they run on the borderline of overheating as it is nowdays.When a modern engine overheats it's really getting hot(260+).


30 years ago running 200 degrees was considered overheating,the KJ's electric fan does not even kick on till 219 degrees.
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Unread 09-23-2013, 08:32 AM   #5
mjb2066
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Thank you all for your replies. I have kept up with the maintenance religiously on this vehicle, and the coolant level is to the max-fill line.

Since I don't know much about cars, why would it only overheat in stop and go traffic if the coolant pump is not working? Wouldn't it overheat under any driving conditions?

Thanks again!
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Unread 09-23-2013, 12:00 PM   #6
olliehopnoodle
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Do you have both a mechanical and electric fan?
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Unread 09-23-2013, 12:16 PM   #7
mjb2066
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My Jeep is equipped only with the electric fan.
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Unread 09-23-2013, 12:21 PM   #8
olliehopnoodle
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okay. I was just thinking if it had both, the mechanical would pull enough air to make the electric fan spin. Ours came with the trailer package and has both fans.

If the AC is not working as well as the higher water temp it would tend to indicate an air flow issue. If you were overheating but the AC was working fine then I would think water flow. The air passess over the condensor first and the temp of the engine will have no effect on your AC. It's also possible the two are not related.

Turn your AC on 'high' and coldest setting and confirm the compressor is running at idle (visual inspection).
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Unread 09-23-2013, 02:11 PM   #9
mjb2066
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The compressor clutch catches and the AC comes on normally while idling in my driveway. The electric fan, however, did not come on when I turned on the AC. Although, I'm not sure its supposed to.
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Unread 09-23-2013, 08:34 PM   #10
olliehopnoodle
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Yes it is. The fan comes on when the A/C is on even when the engine is cold. The condenser needs the air flow to make the AC work.

This totally makes sense. If your fan is not coming on and the problem is mostly when you are not moving.
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Unread 09-23-2013, 10:03 PM   #11
tjkj2002
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Quote:
Originally Posted by olliehopnoodle View Post
Yes it is. The fan comes on when the A/C is on even when the engine is cold. The condenser needs the air flow to make the AC work.

This totally makes sense. If your fan is not coming on and the problem is mostly when you are not moving.
Above 35mph or so the fan does not pull enough CFM to equal/exceed the air entering the grill and passing through the condenser/radiator.In most cases the e-fan will be running with the AC on,but not always,and yes that even includes when the engine is at idle(rare but can be normal).
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Unread 09-24-2013, 07:25 AM   #12
olliehopnoodle
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I cannot think of a reason the ac would be on at idle (or more correctly the compressor) but the electric fan would not. Can you give an example?
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Unread 09-24-2013, 07:59 AM   #13
mjb2066
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Thank you for your replies. It sounds like the fan might be the problem. Is there anything I can do to positively determine this to be the case (i.e. a mechanical or electrical test)? The fan assembly is pretty easy to uninstall.
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Unread 09-24-2013, 09:46 AM   #14
olliehopnoodle
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Disconnect the fan plug. Usea multimeter to determine which side is positive and which side is neg. You will do this with the engine running and AC on 'full'. Make sure the compressor is running too. Once you know which side is positive and which side is on the supply side of the plug you should be able to take two wires and on the fan side of the plug connect them right to the battery. Fan should spin like crazy.

Watch the temp gauge while you are doing this. Maybe use a garden hose and spray the radiator to help keep it cool if this takes longer than you expected.

When all is said and done you might look at adding the mechanical fan into your setup as well. It might hurt gas milage a little bit but otherwise there are not a lot of down sides to having a mechanical fan too. I can take pics of my setup. I don't know if the stock mech/electric fan setup used the same electric fan and shroud as an 'electric only' setup did.
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Unread 09-27-2013, 10:56 AM   #15
mjb2066
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I just connected a multimeter to the fan connection with the Jeep running and AC on the highest setting, as you suggested. It was receiving 13.9 Volts DC, but not spinning. I would say I need a new fan.
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