Any Problem with Switching to a 180º Thermostat in a Dodge 5.9L Gas Engine?

[DonCurley]

I've got a swapped-in Dodge Magnum 5. 9L V8 gas engine in my 2000 Jeep Wrangler 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 5. 2L or 5. 9L gas engine 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

 

[JJPage]

I would also like to go with a 180º thermostat, however, 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.

Thanks in advance,
Don

I believe this is exactly what is going to take place, however the only real noticeable performance difference will be poor fuel mileage.

I did this on my Ford 302, with the recommendation from Superchips to change my t-stat along with the octane bar in the distributor to compliment their box. The lower temp t-stat made the ecm feed more fuel (choke), because it did not believe the engine was up to operating temp. My fuel mileage went to heck, I changed back to the factory stat, my mileage returned and I really could tell no difference in power.

I understand you are asking about Dodge, but I believe they will behave the same... .

 

[Bob4x4]

The Dodge gassers will trip a code if the correct temp is not acheived in the anticipated amount of time unless you reprogram the controller

 

[jgillott]

We used to have a '96 Grand Cherokee with the 318. It has been a lot of years ago now, but I believe that I put a 180 in it when I replaced the hoses without any ill effects.



On Edit: As others have mentioned, it may have effected the fuel mileage. But, that thing on the best day couldn't get better than 12 mpg if you dropped it out of an airplane. At that point, it wasn't relative.

 

[DonCurley]

I believe this is exactly what is going to take place, however the only real noticeable performance difference will be poor fuel mileage.



I did this on my Ford 302, with the recommendation from Superchips to change my t-stat along with the octane bar in the distributor to compliment their box. The lower temp t-stat made the ecm feed more fuel (choke), because it did not believe the engine was up to operating temp. My fuel mileage went to heck, I changed back to the factory stat, my mileage returned and I really could tell no difference in power.



I understand you are asking about Dodge, but I believe they will behave the same... .

I agree, whether for a Ford or a Dodge, I am sure they will behave essentially the same in this regard.



Also, here's a comprehensive write-up on the subject on Dodge Forum ... 180* Thermostats... Pro's and Con's. . - DodgeForum.com



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.

 

[DonCurley]

The Dodge gassers will trip a code if the correct temp is not acheived in the anticipated amount of time unless you reprogram the controller

From what I now understand, going with a 160º thermostat will definitely do this in a 5. 2L or 5. 9L Dodge Magnum engine, however, the 180º thermostat probably won't throw a code. That said, you're still going to run rich, get worse fuel mileage, and get the other negatives that go along with the lower temp thermostat (i. e. , without adjustments from a tuner/programmer).

 

[DonCurley]

We used to have a '96 Grand Cherokee with the 318. It has been a lot of years ago now, but I believe that I put a 180 in it when I replaced the hoses without any ill effects.



On Edit: As others have mentioned, it may have effected the fuel mileage. But, that thing on the best day couldn't get better than 12 mpg if you dropped it out of an airplane. At that point, it wasn't relative.

I hear ya. We also had a '97 Grand Cherokee with a 318. Nice ride, but fuel mileage wasn't its strong suit (nor its dismal repair record).



Trouble is, 5. 9's are even worse in the fuel mileage department than 5. 2's, so I don't want to make a bad situation even worse by going with a 180º thermostat.