Any Problem with Switching to a 180º Thermostat in a Dodge 5.9L V8? - JeepForum.com
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Unread 05-02-2012, 12:53 PM   #1
DECJ
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Any Problem with Switching to a 180º Thermostat in a Dodge 5.9L V8?

I've got a swapped-in Dodge Magnum 5.9L V8 engine in my 2000 Jeep TJ and I am about to do the plenum plate upgrade to my factory intake manifold.

While I am doing this work, I plan to replace the thermostat. I could of course just go with the same 195º thermostat that the factory used for this engine, but I have previously heard that a lot of guys have gone with a 180º unit.

I would also like to go with a 180º thermostat, however, I want to make sure that I am not going to get into any unintended consequences from a performance perspective by doing this. For example, if the PCM is looking for the engine to come up to operating temperature, I don't want to get into any potential fuel mixture or advance curve issues with the PCM wrongly interpreting the lower engine operating temp as an indication that the engine hasn't fully warmed up yet.

So, if anyone with either a Dodge Magnum 5.2L or 5.9L has switched to a 180º thermostat, or is otherwise knowledgeable about the way the PCM looks at the engine operating temp (as a function of coolant temp), please let me know if you have had any adverse performance problems or whether this move wouldn't be recommended for some reason.

Thanks in advance,
Don

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Unread 05-02-2012, 01:54 PM   #2
LJameson
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The problem with going to a cooler thermostat is like you said, the PCM will possibly stay in open loop and not operate as efficiently, dumping more fuel into the engine then it should.

Chrysler designed the engine as a whole unit to run as efficiently as possible with a 195* thermostat. And really, all the thermostat will help with is the minimum operating temperature that the engine will run at. During hot days, it will run at whatever temp your cooling system is capable of keeping it at. IMHO, I'd just stick to the 195* thermostat.
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Unread 05-03-2012, 07:52 AM   #3
DECJ
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Yep, you're absolutely right.

Also, here's a comprehensive write-up on the subject on Dodge Forum ... http://dodgeforum.com/forum/2nd-gen-...-and-cons.html

I also received a response from a Dodge service tech on another board I posted to who basically gave a shorter version of the same information that was in the Dodge Forum write-up.

So, since I don't have a tuner/programmer, I am definitely going to stay with a 195º thermostat as I don't need to get even worse fuel mileage.
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Unread 05-03-2012, 08:11 AM   #4
comptiger5000
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The PCM will still go into closed loop at 180*. It won't hurt anything to run a the 180* stat, other than maybe a small drop in fuel mileage. However, there's no good reason to do it, as the benefits are minimal. Heck, I'm one of the few running a 5.9 with power mods that still has a 195* t-stat in it.
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Unread 05-03-2012, 08:32 AM   #5
DECJ
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Quote:
Originally Posted by comptiger5000 View Post
The PCM will still go into closed loop at 180*.
That's good to know as I wasn't sure what the closed loop temperature threshold was.

Quote:
It won't hurt anything to run a the 180* stat, other than maybe a small drop in fuel mileage. However, there's no good reason to do it, as the benefits are minimal. Heck, I'm one of the few running a 5.9 with power mods that still has a 195* t-stat in it.
I get bad enough fuel mileage as it is, so I don't want to add to that . By the way, here's a shot of my 5.9 going into my TJ. It also has a number of power mods as well ...

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Unread 05-03-2012, 08:36 AM   #6
comptiger5000
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Very nice!
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