4 replies to this topic

[noeman]

I just bought a 74 thermostat As a experiment. I noticed there is a hole drilled in the side with a small ball float. I wondered what the hole and float function is?
Is it to let more flow when the thermostat opens and the ball will drop?

[nicklouse]

That should be on every Mini thermostat it allows the system to bleed.

[noeman]

Ah, that's good. I've got a few thermostats and it's the first time I've come across one like that.

[unburntfuelinthemorning]

Yes it prevents air being trapped underneath the thermostat when the system is being filled.  When I got my van there was some odd stuff going on with the cooling system.  I got a new thermostat and when removing the old one I found it didn't have one of those holes at all.

[Spider]

Some have that hole with a 'jiggler' in them. As Nick and Unburnt have said it does help with bleeding the system. The 'jiggler is there so that once the coolant has reached the Thermostat, the jiggler floats and the hole (for the most part) is closed off, so the Thermostat can do it's job.