Thought I'd post a fresh question on this subject.

Stock 195 thermostat vs. 180 thermostat.

You see my intake body gasket is leaking so I'm tempted to put a 180 in, but the open/closed cycle argument has got me on the fence.

I put in a 180* and haven't looked back.

I got a 180* wish I could have found a 160*

A 180* is great because it isn't too extreme and still allows the grand to reach operating temperature and run within normal range. The thing that is always said with the lower degree thermostats is that it fools the computer. By the thermostat opening sooner and keeping the engine cooler it makes the computer think that the engine isn't getting up to operating temperature around the midway mark on the temperature gauge. To compensate and create more heat the engine dumps more fuel creating more power in the cylinder. I've noticed this idea in the fact that most of the cars and Jeeps i've owned are more "ballsy" in the morning when its colder. This is all the theory behind it.

I think the 180* makes my 5.2L run at the perfect temperature even in the hot days of summer. I don't think dropping to a 160* would be much more beneficial.

run the 195 in the winter, and the 180 in the summer, you will have less problems with overheating on the trail.

A 180°F t-stat [smilie=bal_cool.gif]

I like the 195 for winter and the 180 for the summer idea myself. But remember that a cooler thermostat does nothing except drop you operating temp. If you are running hot, then you need to address this at the source be it air flow, water flow or radiating capacity.

In terms of extra power, cooler air, and therefore cooler manifolds equals denser air and better power too.

Last summer we talked about this a lot. In good health the stock set-up will usually do a great job at least for 4.0's and 5.2's. I have found on these the stock Mopar thermostat does a great job, better than a 195 aftermarket. My 5.2 barely moves it's needle a half a marking be it cold winter or hot summer. Somebody at engineer did a lot of homework and testing on these rigs and set ups. Never owning a 5.9 I can not comment on those. But as things start to age out that is another story.

Is there really a difference once the Jeep warms up? I leaning towards a stock T-stat even though popular opinion is pointing the other way.

Logically doesn't the 180 only delay the warm up? Once the t-stat opens up you introduce the cooler stored fluid in the radiator to the system. Then that heats up so the entire loop is keeping the engine at about 210.

There are certain temperatures at which the thermostat is partially opened and fully opened. If the thermostat fully opens at 180* then it allows the coolant to start working quicker to keep the engine temperature down. If the temp is already up around 210* and then the thermostat finally opens fully its now playing catch up to keep the engine block from overheating. I like the 180* being ahead of the game. Before I installed mine, I had to watch the needle climb past the halfway mark before it would finally start to come back down. Now it never gets up near it.

I had a 160 in mine for about 6 months. ZJ's with 5.2's run rich from the factory as it is, with the 160 even moreso to the point where you start seeing even less mileage than usual (I know hard to believe). When I switched back to the 192-195 I gained about a mile and a half per gallon, back up to a whopping 12.7 :mrgreen:

Exactly same like AndyZJ.

A 5,9 has an electric two speed fan. When t-stat is changed,is better to change the fan switch too.
I have 180°F t-stat and the 200°F fan switch for first speed.Opposite a stock 214°F. Now is better continuity in the cooling

I went from a 195 to 180 to 160 and back to 180. The 160 was just to low, it was fine when the outside temp was in the upper 90's and higher but when it was cooler or on the highway my engine temp was too low. I found the 180 to be just right.

The only time you should consider the 160* is if you've got all kinds of ponies running through your engine. I wouldn't even consider it otherwise. 180* is perfect for the 318 and 360.

When t-stat is changed,is better to change the fan switch too.
I have 180°F t-stat and the 200°F fan switch for first speed.Opposite a stock 214°F. Now is better continuity in the cooling

Interesting,

I actually have been debating an auxiliary fan with a manual cut off for the aux fan in the cabin in addition to a change in T-stat.

I'm running hot at idle and crawling on the trail and need more air flow over the radiator.

A manualy switch I have too.

I'm gonna replace my stat w/180* in my '93 ZJ/5.2L. I read somewhere that you can drill a small 1/8" hole in the stat to act as a "Jiggler Valve" to prevent air lock. Has anyone done this with success? Or can it be detrimental?