Thermostats use and function

[ThosL]

One of the area Subaru specialists installed a really heavy duty looking thermostat in my 2.2 Outback engine when they did the water pump job.  I went to an auto parts place recently asking for an OE unit which was considerably less substantial looking, they both functioned.  I was wondering if you pull out the thermostat leaving the rubber o ring in against leaking if that has any bad effects?

[gbhrps]

thosl,

 

It is ill advised to run any engine without a thermostat. Engines run best at a predetermined temperature that is set by the thermostat (generally 170 - 180 degrees). Running the engine without one, will not give you enough heat for the heater, but worse will have the engine wasting fuel and possibly fouling spark plugs and valves.

[lstevens76]

Actually it's 195 on Subarus.  

 

There has been a lot of time and research put into the "optimum" operating temperature for an engine.  What this calculates in is fuel usage, air usage, how clean the engine burns, is there heat available for the inside (secondary to the first), etc...

 

The optimum temperature for all of these combined on most vehicles is 190 to 195f.  The reason some racing thermostats are lower is an engine will run differently at colder temps whether it is carb or injected and the computer reacts differently to colder temps supply more fuel, etc...

 

What a lot of places consider "OE" is not.  Many aftermarket cheap OE replacements are not as big or as well built as the OEM.  If you search around there's a picture of an OEM vrs an Afermarket thermostat for Subaru's.  It makes the difference very obvious.

 

You have about a month you could safely run without a thermostat, but it isn't going the fix the problem just buy you a little more time "MAYBE" and by running it you could make the problem worse as well.

 

When winter hits your going to want a thermostat in it.  No defrost can really suck.

[Fairtax4me]

Running no thermostat keeps the engine from reaching proper operating temp. Causes wear in the cylinder walls and to the piston rings.

 

Also when the coolant temp is too low the ECU is forced to run in open loop which gives a richer fuel mixture. Poor fuel economy, fouls spark plugs, overheats the cats, washes the rings.

 

 

The real Subaru thermostat is huge. It's that way for a reason, because the larger design doesn't open and close as quickly as the small aftermarket ones. It provides better (smoother) temperature regulation.

[1 Lucky Texan]

most 'fairly modern' soobs use a 170* stat  and it has a larger wax capsule (probably for the thermal mass/hysteresis)

 

 

 

Stant's Xacstat model is probably OK too - it is built like the Subaru model.

Edited September 11, 2015 by 1 Lucky Texan

[desertsubaru]

I used the Stant's Xacstat on my 03 forester. It has worked very well so far. Temp stays at one spot no matter what the outside temp is.

[Loyale 2.7 Turbo]

Running no thermostat keeps the engine from reaching proper operating temp. Causes wear in the cylinder walls and to the piston rings...

 

Isn't the other way around?

 

As far as I know, Hotter temperatures causes metal expansion, and thus gives closer tolerances, and increase shearing; That is why an engine that overheats, looses power: the Piston gets hard to move on a cylinder wall that gets narrower under high temperatures.

 

However, besides that, the Thermostat is really needed to keep the engine at proper operating temps, especially on places where there are cold climates and snows; otherwise, the oil will become Mud inside; it is common to see engines that runs without thermostat, to have much more gunk and mud buildup than the ones that has thermostat.

 

However, you must be aware that usually, the ideal operating temperatures for an engine, are Lower than the ones forced by Thermostats and Thermoswitches; the reason is the Catalytic Converters. Those devices are the ones who doesn't work properly unless the gases are coming pretty Hot, and the Automotive industry has moved the operating temperatures up, since the use of Catalytic conversters.

 

As side information, I run my Weberized EA82 without thermostat, since late 1985 up to date, the car only takes more minutes to reach operating temperatures, but once reached, it stays there all day long; but here in Honduras you have permanent warm climate from the caribbean, and you don't need to have Catalytic converters on your cars...

 

Also my Wife's car, an 1.8L M.P.F.I. runs without thermostat since 2009 ... but that only works well, under stable climate conditions, and using catless exhausts. Your car needs the Thermostat in other world areas.

 

Kind Regards.

[1 Lucky Texan]

thermal efficiency is better at higher temps, less likely to carbon-foul the plugs too. Oils are designed to be at 'proper' viscosity at specific temperatures ,etc.

 

sure, specific engines in specific conditions might benefit from some change to operating temp. But keeping temps in the proper 'range' is best.

Edited September 11, 2015 by 1 Lucky Texan

[matt167]

carbons gritty, and a cold engine makes carbon. Cold engines wear more.. Chevrolet turned the SBC, an engine that used to be pooched after 100-150k miles into a 200 plus engine. They did it by running the engines at 212* and low tension rings and fuel injection

[ThosL]

Good discussion on this topic.  However running the 2.2 without a thermostat I am not getting the overheating or the loss of water which is far more destructive and stressful, it can be a living hell to have to constantly watch the temperature gauge wondering if it is accurate, seeing the needle creep up alarmingly; not knowing what is actually going on and on overheatings, whether I need to let it cool for a half hour and then refill with water.  Forget about $13 a gallon antifreeze, I would just be pissing more money away.  The only real solution I'm afraid is a good used engine which will run upwards of $1500 all in which I can't afford.