[Healeys] radiator over flow problem

[Dave Russell]

Hi John,

I have found that drilling a 1/16" hole through the thermostat "valve" 
cures the no vent problem.

As others have said, there will be about 1/2 quart of expansion from 
cold to hot, so underfilling or using a coolant recovery tank are the 
only ways to handle this.

Dave Russell

John Harper wrote:

>Sam
>
>Is it possible that you fitted a type of thermostat without a venting 
>'jiggle pin'?
>
>I had this problem many years ago. What happens is that with the 
>thermostat fully closed and no way for a small amount of coolant to move 
>around the system and allow warm coolant to reach the thermostat bellows 
>the thermostat doesn't open.
>
>The coolant then boils inside the head. This cases back pressure and 
>forces coolant out of the radiator overflow. Eventually steam or hot 
>coolant will get to the bellows and they will open.. The system then 
>operates normally as you describe.
>
>I suggest that you have a look to see that you have the correct type of 
>thermostat fitted.
>
>Regards