Hey guys. Having some cooling issues. Bought my 2013 used with 100k miles. Typical driving temp is anywhere from 198 to 220 in this Texas heat. The old thermostat failed so I put in a 203 new one. Of course as soon as I did the radiator went out. Extended warranty covered that but I’m now seeing temps sitting from 213-222. Resting it will drop to 210 sometimes but driving it seems to live between 219-222.replaced the brand new t-stat as toy mechanic said it might be defective but I’m still seeing the same temps. Is this normal for a 203 t-stat? Is there a break-in period for these? Sorry if it’s a noob question but I’ve got a 1200 mile round trip coming up this weekend and don’t wanna chance it if it’s not normal behavior. Thanks in advance.

 

2013 what? Clearly not an XJ.

 

You’re right. Clearly NOT an XJ. I thought I posted in the Grand Cherokee forums making it obvious what it was. Sorry for not including specs though. 2013 Grand Cherokee 3.6 2wd.

 

Well, you see your profile block says 99 XJ 4.0 and that's why I asked. Also the 3.6 was important. I have no idea what temp thermo is supposed to be in that, but I believe a 195* is normal and that shows in your 198-220 range temps. If you wanted it to run cooler, why did you put a 203 in it? The thermostat's function is to make the engine maintain the thermo's set point as a bottom temp. Why not try a 180* and see if it makes a difference?

 

Thanks for the info. I never said I wanted it to run cooler. I’m just trying to make sure these temps are normal for a 203 thermostat. Unfortunately, since I bought it used I’m not sure if the t-stat in it before was a 203 or 195. I just know it’s not what I was seeing before. I thought maybe someone with another WK2 might have some useful input on the matter. Clearly that’s not the case. If you don’t know it’s ok. Just don’t answer. Easy as that.

 

Okay, enough said! I was just trying to help. It seemed to me it's running a little hotter than it should. Just my opinion.

 

I'm not familiar with the 2013s or that engine, so I can't help on that, but I will say that thermostats are very often misunderstood. The T-stat does not control the engine temperature. It's not like a house thermostat which has a set point and keeps the temp within a certain range of that point. It prevents the coolant from flowing until the engine is up to the correct temperature, then it opens. Once you are into the operating range, it's fully open, and fully open is fully open. If you run hotter than the opening temperature, the thermostat can't help you keep the engine cooler because it is already fully open. That's all it can do. After that point, whether you overheat or not, the temperature you run has nothing to do with the thermostat. It's controlled by how well the rest of the cooling system extracts heat from the engine, and how fast the engine puts heat into the system. In a properly working system, a balance is achieved and the engine runs at a stable temperature, which will be above the opening temperature of the t-stat.

So, all that to say, running a cooler than stock thermostat will not make your engine run cooler. It will just take longer to get up to temperature, since the coolant starts flowing sooner.

Except in one case: If you do a lot of very short runs where you don't get the engine block fully up to temperature, then you will see lower running temperatures for those few moments. But if you are running more normal distances, nope. It's not going to keep it cooler.


To put it another way, do vehicles with properly operating cooling systems, including the stock temperature thermostat, overheat? No.

So, replacing a faulty thermostat may cure an overheating condition if the thermostat was the cause of the problem (by not opening correctly), but replacing a perfectly good stock thermostat will not cure an overheating condition. Since it didn't cause the problem, replacing it can't cure the problem.

If you are overheating, find the reason it's overheating and fix that problem. You gain nothing from a cooler thermostat, and in fact, you cause the engine to not run properly.