I have a '96 Dakota, that I replaced the radiator, water pump and timing chain at 140k miles. At the same time I replaced the thermostat with a 180 degree unit. I'm an old musclecar guy, so back then, we wanted stuff to run as cool as we could get it... I was tempted to run a 160, but like my heat to work when needed!

Anyway, here I am at 235k miles, and the cooling system is doing great. No leaks, no bulges, nothing bad at all. Motor runs like a top. Most importantly - no blown head gaskets.

My Blazer is currently torn apart getting new heads, gaskets etc. One head was cracked through an intake valve, that head gasket was blown in several places, and the other side head gasket showed signs of being miles away from blowing out similarly.

Sooooo... I'm thinking about putting in a 160 or 180 degree thermostat. I believe 195 is just too damn hot of a starting point, especially in a SB Chevy based engine which has had cooling problems since 1955. These motors fluctuate heat horribly, from "normal" to "oh crap!" sitting at a redlight in July when brand new. So lowering the initial temp should solve the problem or at least slow it down to a safer range.

what say you?

 

Well if the temperature is too low your PCM will try to raise the temp by running richer which gives bad mileage. I have a bad thermostat in now that opens at 185 instead of 195 and i notice a difference in mpg. Also at 160 degrees you aren't getting hot enough to burn the carbon out of your engine. Run a 195 and get good gaskets the stock ones are just crap

 

like cherry stated above. emissions are the biggest thing for reason of operating temp.

 

A 180 or 160 thermstat can be put in...but will need to have the PCM reprogrammed due to reasons stated above.

The PCM expects to see a certain operating temp after a pre-determined operation duration or will set a code plus the mixture will be richen. I too learned this as above with a stuck open thermostat.

Cheaper to just use the stock temp thermostat.

 

i ran a 160 years ago in a truck, seemed to run ok but i remember the heat sucking in the winter time

 

Running a cooler tstat was easier on the older non computer controlled motors cause you didn't have all the sensors and crap to control fuel input and such. I had a bad temp sensor that was reading 20-40deg cooler than actual temp depending on the day and I could smell unburnt fuel being sent out the tailpipe due to the pcm trying to add fuel to what it thought was a cold motor. I would stick with a good quality 195 and call it good.

 

If this is on the 2000 Blazer in your profile.... As mentioned already, the PCM monitors ECT data when determining fuel mixture, (moreso in open loop operation). If coolant temp is low, or the ECT sensor is indicating low, the PCM will richen the mixture, which will cool the engine even more, and destroy fuel mileage in the process. As Lanny mentioned, it can also set a DTC in memory. Using anything other than a 195 degree stat will cause other problems. If you've got a cracked head, it's been HOT. Locate and repair the cause: Make sure there are no lean DTC's in memory, a lean mixture burns hotter and can raise coolant temp and burn valves. It could be that the cooling system has not been maintained properly. The entire cooling system needs to be flushed & refilled every 36K miles, (radiator, block & heater core). There may be a coolant leak somewhere: the lower intake manifold gaskets are a common place to leak coolant. Another often overlooked item is the fan clutch. They're typically good for ~100K miles but have been known to die before that. On a cold start, you should hear the fan "roar" for a few seconds before it quiets down.

 

Three little words. "Open loop mode". When you run F.I., you don't have a choke like on a carburetor. I ran 180 thermostats regularly on carbureted engines. On a fuelie though, the computer thinks the engine is still warming up. Since it does without a choke plate, it injects extra gas to enrich the fuel mixture like a choke would have.

With too cool of a thermostat, your engine will slurp fuel and waste both that expensive liquid but shorten the life of your oil.

In addition, while you have the engine apart, replace the timing chain. A worn chain can make the engine run cool by getting the valve timing off. I had a 3.9 in a Dodge Ram a few years back and when I replaced the timing chain, the engine got up to where it should be. My mileage on a 1/2 ton Ram with V-6 and automatic went from 17 mpg to 25 on long straight highway driving.

 

Running rich will actually do the opposite and make the engine run cooler.

195 degree T-stat is what these trucks were designed to use, and I have learned the hard that running lower than recommended stat temps will give no benefits on modern, computer controlled engines. I don't know if a 180 will give you any problems, but I know from experience, that you will have a permanent MIL if you run a 160 and you will get garbage fuel mileage, not to mention, increase your oil change intervals considerably.

 

This thread is strange....I've been running a 180 degree for the last year with no problems. Put it in after replacing head gaskets. Temp gauge is cooler, no lights, no alarms and no codes. Been running just fine, gas mileage is the same as before.