Okay okay okay (deep breath, shift cigar, blow ashes off keyboard)... as far
as I can make out, the entire purpose of the thermostatic vacuum switch in
the upper radiator hose is to provide a vacuum source to the carbs' bypass
valves only at normal operating temperature. Evidently, it's an emissions
thing.
Here's how I figure it:
1) The thick, green tube goes to the bypass valves (front side of carbs) and
attaches to the thermo switch's right/rear vac port (marked F1). This port
is blocked until the thermo switch warms up and opens it to manifold vacuum
which exists continuously at the forward two ports (marked D&C).
2) Manifold vacuum exists in the two thinner black tubes attached at these
front ports D&C to
- the intake manifold's vacuum port (bottom of front carb),
- the distributor's retard vacuum port.
3) I can't find any use (on a '74 TR6) for the fourth vacuum port (marked M)
at the left/rear on my switch.
The real problem is this I tested my switch in hot water as you'd do with
a thermostat, but I couldn't get that puppy to move at all. Stamped into the
capsule end is "220," but that can't be the opening temperature (water's
vapor pressure at 2200F is almost 18psi).
I can't find a source for a replacement switch, so I reckon we need to fix
this one... hopefully without de-crimping the assembly.
Question 1: Do I understand this thing correctly?
Question 2: How big a hammer does one use to free-up a stuck thermostatic
capsule?
Doug Morris, '74 TR6 CF18kUO, NC
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