Technical Your thoughts on 160° thermostat

What are your thoughts and experience on running a 160° thermostat?
I see this option suggested a lot for engine Cooling problems. My thoughts are that as soon as you go over 160 you're basically running without a thermostat at all.
I understand that 160 will help your engine warm up in a cold day, but once you go north of 160 you have effectively no thermostat at all.

 

Well, that’s what I used to do (run 160)!unti i was told about oil,condensation and sludge.

 

If you need the heater because you live and drive in a cold climate, 180 stats. Other wise 160's are fine. I don't run any thermostats in my Flathead and it doesn't overheat even in high 90's temperatures but I don't drive in the winter. OK, now I'm going to get lots of comments about the water circulating too fast in the radiator.

 

According to info published by Summitt, cyl waqll wear is 3 X higher with a 160 vs 180-195.

 

I've started using 160s just to keep underhood temps down, so fuel won't boil. 180 is better for long engine life, but since we don't drive our cars 100k miles, that doesn't really matter much.

 

Been one in my 56 for the 11 years I’ve had the car. I do mostly in town stop n go and summer with the AC on and can see 180-185. Not one to change just for the winter and I’ve used the heater and defroster with the 160 and it fine. I change oil once a year and the milage varies but usually it’s 1500 miles.

 

I ran 160 for years, didn't have any issues with sludge etc, I keep good fresh oil in my rides. Inside of my motor looks like the day I did the heads 9 years ago. So I think the old oils, more sludge prone. I did switch to 180 because I went to a clutch fan, the clutch fans don't full engage till 195 roughly, so I can say my motor has not seen 200 degrees idling with ac on.

There is 2 thoughts on cycling the radiator to cool it down, and lower thermostat to get things moving faster and sooner in temperature. Both have some valid points... 180 Is a good all around piece. Better heater temps etc.

 

I'm also going to vote 180. Engine gets up to operating temp faster and runs better quicker. Engine temp shouldn't go up more than that if everything is working like it should. If you have overheating issues, something else is wrong and needs to be fixed.

 

I like pretty hot air in the winter, usually drive with the window part way down for the fresh air, 160* wasn't quite enough heat compared to the 180 I have now. In the summer, I see no difference with a 250 inline six.

 

I bought a new GMC Suburban in 1996, it now has over 333K miles on it. Engine has never been apart, there was one recall for an intake manifold gasket replacement. It uses no additional oil between changes and I've used WEX filters. With less than 1K miles on it I installed a HyperTek reprogram software. In the instructions it was stated to install a 160 degree thermostat. The engine still p***es the bi annual smog check and runs as well as it did when new. I have three other sbc powered cars they all have 160 thermostats. I personally believe that oil temperature is more important than water temp, but that's another subject.

 

160 is the degree that the stat opens . Once it’s open your engine has no idea if it has a 160 or 190 degree stat . I have for years took the guts out of a stat and ran the washer . There is a lot of mis thinkin about a thermostat . Because you run a 160 doesn’t mean your engine will maintain 160 . As stated heating up the oil to remove junk is not such a bad idea . After of fact , it’s better to be at 190 than 160 for engine life .

 

I've run a 160 for decades in the 283 in my '34. Dropped the oil pan for a new gasket after about 30 years and found no sludge. I do change the oil yearly.

 

Cylinder bores wear faster at cooler temps....see how much wear there is at 100k miles, then you'll know. But if you don't put that many miles on it, you'll never know, and it won't matter.

 

Depends on the engine and what the OE used.
I drive the **** out of old engines. If the OE used a 180/19/195 then that’s what I use.
If it runs hot then there’s something else that needs attention. Not the thermostat.

 

older drivetrains can keep cooling system from too much pressure....head gaskets ..etc...

 

The thermostat is only one part of engine heat control. Thermostat controls opening and full flow, but doesn't really control overall engine temp. Contributors to overall heat are oil temp and expelling heat from the engine compartment (radiator fan and hot air escape), so concentrating on the thermostat is misleading.
Get the engine to operating temp and check oil temp, and use a clip-on oven thermometer to check under hood temp. I use a 160* stat in my 327 powered '51 pickup with no problems (it typically runs about 170* cooling temp), partially because it's now producing the heat of approx 300 hp vs. the 95 hp stocker, so under hood temp is higher than stock. Needless to say, the temp of the overall 'system' is what's important. If it ain't broke.... don't fix it!
Side note..... when choosing a thermostat, look at the size of the 'open' flow path.... there are wide variations between manufacturers), and before installing, check the actual opening temp in a pan of water on Momma's stove. Observe the opening rate and full-open temp.

 

A thermostat has very little to do with an engines maximum temperatures. It's job has more to do with getting the engine up to the acceptable minimum operating temperature quickly, and then maintaining that minimum temp. If the engine temp starts to drop (think cold weather), the thermostat will start to close and restrict coolant flow, thus keeping the engine temp from dropping below operating temperature. Above the desired operating temp, the thermostat will be fully open, and will have no effect whatsoever. It is then the job of the cooling system to moderate temperature.

Put simply, the thermostat is responsible for achieving and maintaining minimum operating temp only.

Such a basic part, and so often misunderstood. I am sure some people think they are magic.......

 

On cold days, the engine will run right at thermostat temp if the cooling system works right and the block is clean. Even on warmer days, the engine still shouldn't get to far above the thermostat rating with a properly working cooling system. The front cylinder of the Chevrolet inline sixes have more wear then the other five due to the water pump location and cooler water hitting the cylinder.

 

That’s something I’ve never thought about, I suppose all inline engines show this as well?
Does that also affect say, 1 and 2 more on a Chevy V8?

 

This discussion has occurred within circles I'm in; my inline 8 has a large folded br*** tube that runs from the outlet of the water pump to the back of the engine, and has holes in which direct the coolant flow at each exhaust valve along the way. From there, the coolant can then just circulate the block and up into the head and back to the radiator.

Without that distribution tube the rear of the engine has a tendency to be at the correct temperature while the front is significantly over-cooled, leading to thermal stresses and eventual cracking of the block between the cylinders.

So, large flow can be a problem when the engine is not doing a lot of work, opening up to the radiator instead of just retaining internal circulation only benefits to warm the block up more slowly in a lot of cases.

As others have said, if you are fighting an engine that runs hot, fitting a lower temperature thermostat only extends the distance you can drive a little- if your cooling system is up to spec then under light load I would expect to see it hold 160 degrees- if it climbs and continues to do so it's time to start poking at the system as a whole.

Sediment blocking the coolant path? Partially blocked radiator? Broken vanes or key on the pump? Especially if it is a recipe that others have used successfully in terms of engine/radiator/transmission/rear-end/climate.

Phil

 

Happens on V8 engines also. I've worked on quite a few engines, first thing I do when ***essing a block is to feel how much ridge there is at the front of the front bore, wear is always greatest there, because that's where the block is the coolest. If you don't believe it, find a collection of old blocks and see for yourself.

 

Number 1 is always cooler than being number 8 right?

 

If you can reliably run them at 190º or so, that's best as it lets the oil also get a lot warmer than if you run a cooler thermostat. The critical issue is that you have a radiator, water pump and airflow adequate to keep it at that temperature. Too many of the vehicles we build run on the hairy edge of overheating if conditions such as weather, traffic, load on the engine, etc. work against us from time to time.

The downside to having too much radiator cooling is that the coolant temperature is significantly reduced by the time it reaches the bottom (or cool side in a crossflow) of the radiator. There is increased thermal shock when the coolant is sent back into the engine due to the difference in temperature of the engine and that chilled coolant. A fan clutch (or thermostatically controlled electric fan) can help to reduce this shock by controlling the airflow through the radiator.

 

I'm in the middle of most of the choices. I run 170 stats in all of my old cars and trucks. I'm not certain what advantage there is to aid in cooling with a 160 stat? I've not seen any vehicles that didn't run warmer than that, so having it open earlier wont avoid overheating, it will simply open sooner and maybe delay the higher temps for a few minutes at best.

 

I just got done with a long road trip with an old Rambler, which has a pretty good cooling system. I put a 160 tstat in it, and it ran at that temp most of the time. The exception was on the highway when it was hot out, and climbing long grades, it would go up. But cool down immediately when going downhill, or in slower traffic. So, most of the time this engine is running pretty cool, and probably getting a bit more cylinder wear than if it had the correct 180 tstat in it. Over the course of a decade, if the car were driven daily, this could make a slight difference in how soon the engine would need to be rebored, to keep it going another decade or two, in regular daily use.

Notice that the concepts of "decade" and "daily use" are totally out of the real life destiny of this car, so it makes zero difference what thermostat I use in it.

 

As has been mentioned, colder engines wear faster.

It's not just a sludge issue. PCV systems and modern oil seem to handle that nicely.

Run the hottest thermostat that you can without overheating.

Complete combustion, depending on the engine, does not occur until the coolant is at about 205°, and sometimes higher.

If you engine is not there, you are putting unburnt fuel out of the exhaust, lowering both power and mileage, all while draining your wallet.

 

Yep, when we were young and dumb (70's) and read too many magazines, we thought cool (many times "boat") thermostats, 50 wt oil in our warmed up stock engines, cold plugs etc., and thought we were cool. Nowadays a 190 or 195 thermo will help keep temps consistent and burn off moisture and bad doodoo, oil viscosity appropriate to bearing clearances, and educated plug choices

 

If only they made gasoline how they used to, it would be fine to run a 195 thermostat. But that doesn't seem to work out too well.

Something's gotta give.

 

I’m running a return line from the mechanical pump on one engine. 180 stat. No vapor lock issues.
I need to reroute or insulate the fuel line on another. It shows slight vapor lock signs occasionally. Running a 190 stat. The mechanical fan is about 6 inches from the radiator and no shroud. I plan to build a shroud. That should fix the higher temp change when not moving. It doesn’t run hot but fluctuates more than it should.
the one with the 180 stat seems to run too cool
Runs a consistent 185 degrees. I’d like to see that around 210. It’s a big caddy. From what I read, gm changed to a 195 stat in the mid 70s. I plan to change to that and see how it does.
Its strange how each system can have different results. An engine running a 160 stat could run a consistent 190, my 180 in the caddy runs a constant 185, the 350 with a 190 stat runs 210ish.
lots of variables: engine design, load, timing, accessories, fan type, radiator, ………
There are more than one correct answer.

 

Yup. And as long as you can drive it OK under most conditions, it really doesn't matter which one you use.