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05 WK 3.7 4wd
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Discussion Starter · #1 ·
Hi all, new to the forum. Bought a 05 jeep grand cherokee with 229k miles and a blown 3.7 vin k. Swapped in 3.7 from 06 dakota vin k. passenger cylinder head was damaged (please dont ask how, I bought a chrsitine and yeah tig welding didnt work out as planed, lasted 45 min run time before letting go), so ended up replacing it with a reman ebay head . Long story short installed head in frame and fired it up, bled cooling system, checked all systems and accessories. All looks good. Its been 2 weeks and over a 1000 miles but the problem that keeps bugging me is the fluctuating temp. When driving in clean air on highway or city with no traffic its pegged at just over 1/4 to half. When idling in traffic in or park it climbs to just below half and then the fan kicks in and gets back to same positions. It never goes over half. Coolant level is fine and not burning oil. I am just not happy with it fluctuating. Please any advice would be great.
 

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18 WK2 Trailhawk
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603 Posts
Is it possible the temp sender unit is going bad showing a much larger swing of temp then actual? Have you checked the actual temps while the vehicle is running with a scan tool or similar device that would show actual temp variations?

I'm not saying there isn't possibly an issue but a bad 18 year old temp sender is very possible.
 

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05 WK 3.7 4wd
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4 Posts
Discussion Starter · #3 ·
Thats what I was thinking, the dakota's set up is clutch fan, while the jeep is electric. Don't know whether that has something to do with it. the part numbers match for the thermostats, dont know about senders. Will double check and see. Installed a new water pump as good practice. If it is not a sensor issue, then maybe a latent head gasket issue.
 

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05 WK 3.7 4wd
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4 Posts
Discussion Starter · #4 ·
Is it possible the temp sender unit is going bad showing a much larger swing of temp then actual? Have you checked the actual temps while the vehicle is running with a scan tool or similar device that would show actual temp variations?

I'm not saying there isn't possibly an issue but a bad 18 year old temp sender is very possible.
Yeah, I did run a scan through out the start up,didn't go past 215 and cools back down.
 

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603 Posts
Not totally sure but I'd guess that the mechanical fan is the biggest difference. The stock electric fan probably had two speeds to keep the temp more stable, now with the mechanical fan its taking a bit of heat to get the fan clutch to engage then dropping the temp all at once.
 

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05 WK 3.7 4wd
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4 Posts
Discussion Starter · #6 ·
Makes sense, I have the opposite set up here though. The dakota's cooling system is fan clutch with same thermostat and sender as the jeep is with a electric fan. I just swapped the engine in from the dakota to the jeep. Thought thermostats will be different, but they are not according to specs and part numbers (not sure). I am guessing fan clutch is more of a linear drop off compared to electric. You might well be right, I dont think the dakota's fan clutch is electronically controlled. So might be the sending unit.
 
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