lower temp thermostat - Toyota Nation Forum : Toyota Car and Truck Forums

TheKevin · 06-28-2009, 12:55 PM

are there any drawbacks going with a lower temp thermostat?

for example, going with 170* instead of the stock 180.

Stillrunning · 06-28-2009, 03:33 PM

Why?

96CamrySport · 06-30-2009, 09:56 AM

yes. Lower temperatures cause richer running - car runs rich anyways, but your fuel mileage will drop. Heat output at cruise during the winter will also suffer, but i doubt that matters in CA. Some vehicles will throw a CEL if the car doesn't get up to a preset temperature.
The cooling system works just fine as is unless you're running tight auto-x circuits, when the single core radiator gets overwhelmed. If you want to do it anyway for some reason (like nitrous) then you should be able to find a same-size thermostat (52 or 54mm, can't remember which) or you can drill a small hole in it.
Since you're posting this on the gen 3/4 forum, I'm betting the 'stat is a 190F anyway.

If you want to improve your cooling for cheap, I'd recommend washing off the fins of the radiator from the back side and adding Water Wetter.

mspringer · 07-01-2009, 05:52 AM

You know, this is one of the better questions that I have seen on this forum. Its just too bad that you haven't gotten any good feedback.

I have been running a lower t-stat for over a year now, with nothing but good results. I am in the Houston area, where it is much hotter than your area, but I doubt that will make a lot of difference sitting in traffic with the engine running. I had no problems when it was 30 degrees this winter and snowing (ok, barely, but it was snow...), either.

In my opinion, at least the 4 cyl Camry is on the ragged edge of adequate in terms of cooling system design. So, the lower t-stat can help, especially when it is hot (summertime).

Using a scangauge II, before any changes, my car was running between 205 and 215 with the a/c on and under normal driving conditions. Now, I'm an older V8 musclecar guy, but that seems hot to me, although, for emissions purposes, that is probably what they want it to run at. However, with all the complaints of "sludge build-up" in these engines, heat, would seem to me, to be the enemy. (Sludge is usually associated with oil breakdown, due (in large part) to heat.)

First, I changed the radiator (due to the infamous cracking tank issue), which made absolutely no difference in temps, and yes, I use that stupid red Toyota coolant...

Second, I changed the t-stat, from the stock 180, to a 170. (Note - 10 degrees is not enough of a change to trip the low coolant temp codes). I did notice a somewhat longer time to reach 200 degrees, but it still got there, running overall maybe 5-7 degrees cooler overall.

I was still not real happy with running 200 degrees @ 70 mph with a 170 t-stat. At this shop I used to work at while going to college, my mechanic friend always told me that if the cooling system was operating properly, and adequately designed, the car should run very close to the t-stat temp when in motion, so 200+ degrees bothered me.

Next, I looked at the ridiculous transmission cooler - the one-row at the bottom of the radiator. This seemed to me to be an issue, as transmissions run well over 200 degrees, there are two issues - 1, the transmission is not really being adequately cooled, and its lifespan may be shortened, and 2, the transmission fluid is heating the radiator.

So, I went out and bought 5 or 6 add-on transmission coolers at Autozone and O-Riley's, and crawled under the car and test-fitted until I found one that I liked. The cooler I ended up with is a medium-duty towing cooler for a truck, it fits well, and covers about 25 percent (maybe less) of the radiator opening. I ran the cooler in series with the factory cooler (factory cooler, then aftermarket cooler, then back to transmission). Coolant temperatures dropped significantly. My car runs at 186 degrees now, almost all the time. You have to really sit and idle for a long time to get the temps to move up close to 200 degrees.

I have never had the check engine light come on. Fuel economy has remained UNCHANGED, and I don't really think performance changed, except I think the transmission shifts a little more firmly due to the lower fluid temps (slightly thicker, I think), especially in the winter.)

As background, I bought the car about 3 years ago, with 60k miles, it now has 125k. Since purchasing the car, I only run Mobil 1 oil, 10w30, and premium gasoline (some will argue that is a waste, but I don't think so). Last week I changed the (leaky) valve cover gasket, and the inside was clean as a pin - no sludge. My car consistantly gets between 23 and 26 MPG, with 18 inch wheels, and I check the mileage with every fill-up. If I drive it a long distance, out of town, I get 29-30 mpg if its sustained highway driving. You can add 2 mpg for the stock wheels. (In other words, I lost 2 mpg with the wheel change - extra unsprung weight!) The motor is completely stock, except for a generic short ram intake from e-bay (Injun, I think, with the metal tube, which makes the car sound like a giant vacuum leak).

I hope this helps you. In short, you won't see huge changes with the lower t-stat, but there is nothing wrong with doing it - it shouldn't negatively impact you in any way, and if you are changing it anyway, I'd use the 170.
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