----- Original Message ----- Date: Sat, 31 Jul 2004 09:05:22 -0700
From: "Randall" <tr3driver@comcast.net>
Subject: RE: thermostat specifications
>> My original thermostat was a 165 degree skirted bellows unit. the ROM
>> specifies a thermostat which begins opening at 158 and is fully
>> open at 180.
>> So, does this correspond to a modern 165 degree unit or a modern
>> 180? I was
>> unable to find the complete data on any thermostats on the net....
>
>Neither, really, modern wax pellet thermostats open much quicker (over a
>smaller temperature range) than the old aneroid ones did.
>
>I've talked before about the pitfalls in looking at shop manuals to
>determine what parts should be on your car ... here is another example.
>According to the TR4A factory Spare Parts Catalog, the 4A used a
non-sleeved
>thermostat, P/N 140970. I don't have specs for that one, but I do have a
>factory supercession list that shows P/N GTS111 as a replacement, which is
>an ordinary, non-sleeved, 180F (82C) thermostat.
>
>Randall
Wow. that is very interesting. I guess that is why Triumph Rescue used a
180 degree non-skirted thermostat. I wonder if the supercession numbers were
based on a product mananger's comparison of non-comparable specifications,
or an engineer's decision based on experience. If I were very very
motivated, I might consider monitoring the actual coolant temp with the old
bellows thermostat, and then see what it reads with a variety of
thermostats. To a degree (hahahaha) one can do this by watching the temp
gauge.
As I and Jerry Van Vlack have found, the 180 degree non-skirted thermostat
"works", but obviously the engine is running hotter than the temp gauge says
is perfectly normal. The gauge runs at 3/4 rather than the normal 1/2.
However, when driving with a perfectly clean radiator, and a relatively
clean engine, the temp did not rise much even in mostly stopped traffic.
But I would rather have the engine running at the "normal" operating temp to
give me 20 degrees more cushion in overheating. Plus, I would rather try to
direct more flow to the radiator and away from the bypass hose by having a
skirt (if it actually does anything).
When I tested the old and new thermostats I did not notice a narrower range
in temp sensitivity for the new wax-type thermostat, but I was raising the
temp fairly fast and the bellows type responds so much faster that I
probably would not have been able to see any difference no matter what. I
guess the new thermostats will cause wider swings in coolant temperature
than the old type (it reacts slower allowing the temp to climb higher, then
opens wide and the temp plummets and keeps dropping until it finally reacts,
then closes up a lot and the cycle starts over).
All theorizing aside, the engine seems to be very happy with the new skirted
thermostat and the pointer rests just about exactly at the first tiny dot on
the gauge which is almost perfectly 1/2 way on the dial.
-Tony
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