Thermostat

[Sunset Six]

I just installed a stant 180, when I removed the stock 195 I noticed it had a little hole on the flange of the stat for coolant to bleed through.Whats this hole for? The replacement thermostat didn't have it.

[TwoTealTerrors]

The little hole is exactly what you said a bleeder valve. If there was any air in the system it would escape through the hole. It is not a necessity so if youre new one does not have it, its nothing to worry about.

Later,
Mike

[Dominic]

Actually the hole is what makes the stock stat a 195.

Each one of those holes is approx 5°F drop in temp when you see how the thermostat acts.

They install a 200°F spring stat and have a hole drilled in it to make it 195°F.

Do not worry [img]smile.gif[/img] All is normal.

[67-03 RIP]

<blockquote>quote:</font><hr>Actually the hole is what makes the stock stat a 195.
Each one of those holes is approx 5°F drop in temp when you see how the thermostat acts.

They install a 200°F spring stat and have a hole drilled in it to make it 195°F.

<hr></blockquote>

Would that mean if I had a hole or two in a 180 stat I'm getting ready to put in it wouldn't open at 180 (1 hole = 175, 2=170)??? Assuming the same size hole.

Ron

[Dominic]

No it would still open when the temperature reaches a critical point.

The thing to remember is these are temperature controlled spring valves... a 180F stat might be slightly open at 178F, and fully open by 190F.

What the holes do is allow a little bit more flow until its fully open, and that is like it being more open even though it isnt. (Does that make sense?)

[67-03 RIP]

Ooops -
Yea, didn't mean it changed the opening point of the spring.... Thanks for the clarification Dominic - that made sense. We did a trick with our "old" 350 in an 84 I had (NOT original). Those had a bypass in the block/water pump to avoid pressure build up before the stat opened, so to get slightly better pump flow, we tapped that hole and plugged it with a pipe plug to force all the water through the pump impeller and then drilled four holes in the stat housing to avoid the pressure build up.

Thanks again Dominic - good explanation.

Ron