Thermostat

[Brian Cole]

Is the hole with the valve in the thermostat a bleed valve or a drain whic affects its position?

[Leo Bolter]

Hi Brian.

Edited after reading your other post (Distributor - Water loss http://jowett.net/forum/viewtopic.php?f=1&t=2290).
I believe it's been found to be beneficial to remove any valve that would stop the water flow as described below . . in fact I seem to recollect that some have found the need to enlarge the existing hole or of course, drill one if there's not one in the main valve or outer disc already!

I habitually install the hole in the thermostat to the topmost position as it would allow nearly all the air to vent through it when the empty cooling system is being refilled . . . it probably doesn't matter where it actually is, in fact.

After the system is refilled and the engine is initially running (i.e., cool coolant and thermostat closed) the hole allows sufficient flow through it (the flow driven by the water pump) so that the thermostat is able to sense the coolant temperature . . otherwise the thermostat is in a "blind pocket" at that stage of it's operation sequence and would be delayed in it's opening. Well, that's my theory anyway

Incidentally, there's probably no supplies of the old bellows type thermostats available these days anyway, but they were inclined to fracture at the convolutions of the bellows and subsequently "fail shut" (and the engine would overheat!). The more modern Waxstat type has a plunger to actuate the valve so are deemed to be more reliable . . . if they do fail, they are reputed to fail in a open state . . . don't believe it (unless your water pump is able to produce plenty of pressure!).

You know, of course, how to check a thermostat by standing it in a pot on the stove and slowly bringing it towards boiling point and observing the fully opening (and closing, with the heat source turned off). A suitable thermometer aids in the verification of the opening temperature marked on the "bulb".

Regards to all.
Leo.