[alfa] Re: 115 spider cooling system saga bypass valves

[Jon Pike <jhpike@xxxxxxx>]

Hmmm...  I read the article,  and as it looks to me,  the flow 
restrictor still has some use.

It isn't just a basic restrictor of a single hole.  It is an aprox 1/8" 
orifice, in a spring loaded plate of maybe 1/2" dia.  So, when the 
thermostat is fully closed,  the pressure overwhelms the spring pressure 
and you get a big bypass flow thru the engine as it warms.  Then,  when 
the thermo starts opening,  the pressure goes down,  the bypass valve 
closes,  leaving the smaller hole for less bypass flow,  eventually the 
thermo opens fully and at the same time blocks the bypass for full 
radiator flow.

Possibly the limited bypass flow helps the thermostat block plate close 
off..

Anyway,  this I figured out by looking at the old one I have laying 
around in a hose from my basket case motor.  So, I'm sold...  and want 
to put it in a new hose for my rebuilt motor.

$100,000 question... how the heck do you get this thing into a new 
hose,  when it looks to be 20% larger in diameter than the hose?  Boil 
the hose and use a speculum??   Or can you still buy bypass hoses with 
them embedded inside?

Jon


>  Rich Hirsch's excellent article at 
> http://www.geocities.com/motorcity/downs/3837/bypassco.html is good reading if you haven't already seen it.  The 
> only thing I'm muddy about is the fact that the thermostat is acutally a "dual 
> mode" design that is supposed to BLOCK the bypass hose in the fully open 
> position (that's why generic thermostats from Grand Auto or Kragen don't really work 
> on Alfas).  So it seems like the function of the restrictor is a little 
> redundant - it regulates the circulation when the thermostat is closed (but who 
> cares since the radiator is not in the loop) and flow to the restrictor is blocked 
> by the thermostat when the thermostat is open.  So I am actually puzzled - 
> unless Alfa designed the flow restrictor before they developed the dual action 
> thermostat and the restrictor was left in as a "prehensile tail".  But I never 
> took mine out for fear of what Fred might do to me if he ever found out!  ;->
>    Hope this helps somewhat.
> Cheers,
> Charlie 
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