Does the thermostat have to be put in facing a certain way?

[AlpineRob]

Obviously the small end of the thermostat goes into the motor first. but my does it have to face a certain way in the other direction? there are no arrows on mine..?

[cristimm]

If it has no arrow then this picture should guide you - look at the yellow brace vs where the arrow should be.

http://z.about.com/d/autorepair/1/0/2/-/84902118.gif

[RED IS 91]

The spring goes towards the head.

[PumpItUp]

wahler on right
behr on left (after i drilled my own hole through the arrow)

i still never got an answer to this question. does the thermostat have to be tilted a certain way if it has no bleeder hole, it will still have an engraved dot or arrow which "should be pointed up" when installed. but for what purpose???

[rac3r]

The Bentley manual says: "Some thermostats have a direction arrow or vent hole near the edge. Install the thermostat so that either the arrow or hole are at the top."

There is a photo that shows the thermostat installed. The thermostat is clocked such that the the "arch" runs from 12 o'clock to 6 o'clock. I have mine clocked as such and have had no issues.

The manual also does instruct to note the existing thermostat orientation before removing it. It makes it sound like the proper clocking is somewhat of importance. My guess would be that an improper positioning of the arc can impede coolant flow.

[DesktopDave]

Having done this on my car, I'd suggest that the thermostat arch should be horizontal to the ground with the body of the thermostat inside the block.  I'd also suggest mixing more distilled water and a surfactant (like water wetter or purple ice) into the coolant, up to 75% water by volume.  Higher % water will improve heat transfer from the engine.  My philosophy is to use just enough coolant to prevent freezing, and change it often enough (every year or two) to prevent corrosion.

If our thermostats had jiggle valves or bleeder holes orientation would matter more, but IMHO it doesn't make an incredible amount of difference either way.  Even putting the thermo in backwards won't stop it from working properly, it'll just cut down on efficiency.  I'd suspect that the thermostat has no bleed hole by design...as the thermostat housing has a bleeder passage cast into the mounting flange.  I'd assume that this requires the OEM paper gasket to work properly.

I'd also suggest avoiding silicone goop in the cooling system, but if you must...then drill a small hole in the top of the thermostat...that bleed passage isn't critical but definitely makes bleeding more difficult if it's not clear.