"CLASSIC CARS, thoroughbred &"

[Mike Wattam <101714.1343@domain.elided>]

Dear Chuck

The sender unit you refer to in the back of the cylinder head was a
'normal' sender unit,set to operate at around 95 degrees Centigrade.  This
would have been fine with an engine which is able to run at normal
temperatures, but the Stag when worked hard will routinely run at around
95-100 degrees without boiling.

Because the cooling system is heavily pressurised to 20psi on cars with a
pressurised overflow tank, the boiling point is about 115 degrees.

There is no doubt the sender could be used, but we would have to find a
sender unit with a higher temperature closing point and having made some
enquiries a few years ago, I could not find a suitable sender.

The end-game is that because Triumph could not get the engine to run
without boiling on Mk1 cars, they raised the cooling system pressure to
stop the boiling.  A classic case of attacking the symptoms, and not the
cause.  

I believe nearly every car sold in the USA was converted to the Mk2 system
because of this.

Mike Wattam
Triumph Stag Register