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Author Topic: 2001 GC V8 running too cool?  (Read 226 times)

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andypalmer

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2001 GC V8 running too cool?
« on: December 03, 2017, 12:52:27 PM »

Hi all,

I have a 2001 Grand Cherokee V8 and I'm not sure whether it's running warm enough. It's LPG converted if that makes a difference.

It's currently showing the mark one to the left of centre on the gauge, unless I boot it or I'm stuck in traffic for a while in which case it creeps up near the centre mark. This is even after my commute of around an hour. Even in summer it only gets to the centre mark under heavy load or in traffic although then it can creep just over the centre mark. It does seem to get up to temperature OK as it switches to gas within 1 1/2 miles even when below zero outside. Is this normal?

My main reason for asking is that I don't get HOT heat until it gets near the centre mark and I wonder whether the two are related. I've had the blend doors done, coolant flush and new thermostat (all Greg at 4Play) . Greg told me his V8 (HO admittedly) runs at the centre mark all of the time.

Is there anything I should be checking?

Thanks in advance.
Andy
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Andy

2001 Grand Cherokee Limited V8

bigjeepzj

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Re: 2001 GC V8 running too cool?
« Reply #1 on: December 03, 2017, 01:10:16 PM »

Hi have had that type of problem on other motors and it's the water pump on the way out. Is the engine block feeling like it's getting hot
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andypalmer

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Re: 2001 GC V8 running too cool?
« Reply #2 on: December 03, 2017, 01:46:45 PM »

The whole engine bay gets warm but not what I'd have thought was TOO warm, is there anywhere in particular I should check? Should this be just after warm up? This is my first V8 and first Jeep so I'm not sure how warm it should be, given the amount of fuel it uses I'd assumed it should get relatively warm.
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Andy

2001 Grand Cherokee Limited V8

bigjeepzj

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Re: 2001 GC V8 running too cool?
« Reply #3 on: December 03, 2017, 06:22:01 PM »

another thorough have you burped the system. take off the radiator cap and run the engine till i warms up so any air can come out ?
   
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andypalmer

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Re: 2001 GC V8 running too cool?
« Reply #4 on: December 03, 2017, 07:19:51 PM »

I've bled it from the top hose bleed point but not tried withe rad cap off. As my thermostat is in the bottom hose would it work? I assume that I'd need to just keep the rad topped up if the level drops and put the cap on after a few minutes of running?
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Andy

2001 Grand Cherokee Limited V8

donk498

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Re: 2001 GC V8 running too cool?
« Reply #5 on: December 03, 2017, 09:15:47 PM »

The 4.7 can be a pain to bleed. Park it facing uphill and remove the bleed screw when filling.
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andypalmer

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Re: 2001 GC V8 running too cool?
« Reply #6 on: December 04, 2017, 06:15:50 AM »

I'll try both this weekend, my drive is about 20 degrees so that should work.
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Andy

2001 Grand Cherokee Limited V8

Mike

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Re: 2001 GC V8 running too cool?
« Reply #7 on: December 04, 2017, 10:57:48 AM »

If it has a viscous fan, make sure the clutch isn't stuck.
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andypalmer

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Re: 2001 GC V8 running too cool?
« Reply #8 on: December 04, 2017, 02:48:44 PM »

Fan is hydraulic on mine. All of the suggestions are things that I'd have thought would cause overheating rather than the opposite. One thing to add is that heater gets warmer if on re-circulate but that's no good if i want to de-mist the screen.

If re-bleeding and burping don't work is there any way to test the water pump, short of pulling it off?
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Andy

2001 Grand Cherokee Limited V8

carljh

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Re: 2001 GC V8 running too cool?
« Reply #9 on: December 06, 2017, 02:04:24 AM »

If you put the heater into diagnostic mode (hold the recirc and demist buttons in and turn the left temp knob 1 click clockwise)
then turn the left temp knob till it reads 66 then press the recirc button it will show the coolant temp the sensor is sending to the ecu in F.
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andypalmer

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Re: 2001 GC V8 running too cool?
« Reply #10 on: December 07, 2017, 06:20:52 PM »

I haven't had time in daylight to bleed or burp but I have tried the diagnostic mode. To sum up it warms up nicely to an indicated 199. It then hovers around 199 to 201, up to 204 when accelerating or down to 197 when coasting. Sitting at traffic lights with my foot on the brakes it touched 210. When around 204 or over heating felt warmer. Do these figures sound right at 7 Celsius outside? I thought, as the stat is a 195, that it would sit around 205 myself.
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Andy

2001 Grand Cherokee Limited V8

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Re: 2001 GC V8 running too cool?
« Reply #11 on: December 07, 2017, 08:22:57 PM »

The temps are about the same as my 4.7 HO, the FSM says to fill the system until coolant comes out the bleed hole, put the plug back and fill the radiator right to the top, put the cap on and fill the expansion tank to the line. then do several heat/cold cycles to get the air out, topping up the expansion bottle as needed.
Jeepforum members suggest the better way is once filled start the engine and give it a few revs to circulate the coolant. then take the plug out and fill again. repeat until you cant get any more in without it overflowing.This way the engine doesn't get hot before you've got all the air out, apparently the V8 can get an air pocket in the block which is difficult to shift without reving it. I did it this way when i put a new water pump on mine, took 3 goes to get it full. The last thing you want is low coolant and air pockets in these engines and it overheat, it will kill it.
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