58 3A constantly running hot like so many of these cars even with
supplemental electric fan. I took apart the thermostat housing and noted
that previous owner had replaced with a modern thermostat which fits and
opened properly at temperature in the water bath. However, the
thermostat lacked a sleeve that was apparently found on the original
thermostats which, when open, covers and blocks flow to the shunt from
the block return back to the block coolant inlet. This shunt has coolant
flow only when the car is cold and the thermostat is closed and no
coolant is goint to the radiator. This shunt is closed off by the
thermostat sleeve when the thermostat is open forcing all flow to the
top of the radiator. The replacement thermostats without this sleeve are
cheap ($5) whereas the original-type replacement with sleeve is much
more expensive (about $35, Moss) so I imagine most folks go with the
cheaper version. The original type thermostat also has a much bigger
throat opening when fully open so flow to the radiator is better and the
shunt around the radiator is blocked. So I put in this new
"original-type" expensive thermostat and the car runs much cooler. I bet
I am not the only one. Is this a well-known issue?
Rich
TS26412
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