[TR] Explain This Overheating

[Dave1massey at cs.com]

Check your radiator cap.  I had an overheating problem in one of my cars 
but only at altitude (6,000 ft and higher).  The cap was not holding pressure 
and I would get boil over even when the car was just at normal operating 
temperatures.  

A new cap solved the problem.

Dave

In a message dated 3/13/2013 12:19:28 PM Central Daylight Time, 
wsb1960tr3a at att.net writes: 
>      So I've begun driving the TR3 to work again. It has been in the 80's
> during the day in Mojave. It is pretty brisk at 0600 at the mile high
> elevation that I live at.
>      The temperature gauge in the TR3 has lost the
> ether and is getting sent in to be rebuilt asap.
>      So yesterday I am
> driving home. The TR runs like a freight train. I coasted down about 1/2 
> mile
> and downhill and stopped outside my garage. While the garage door is 
> opening
> the car overheats and steam comes out.
>      I topped off the coolant. Later
> that evening I let my daughter drive the TR with me in the car with her. 
> We
> are tooling around the hills at low speeds, under 35 mph. We coast down 
> about
> a mile of downhill and stop at a stop sign. I begin smelling hot coolant
> again. It is like it is taunting me.
>      My radiator was rebuilt about 12
> years ago without a crank hole.
>      I have blocked off the water pump bypass
> with a brass plug with a 1/8" hole drilled in it to prevent vacuum lock.
>     
> I have an electric fan (puller, not pusher) that comes on at about 190.
>     
> Tonight I am going to use a Prestone radiator flush and refill with fresh
> coolant and distilled water 50/50 mix.
>      With the coolant out I am going to
> pour water in the top to see how fast it sloshes out the bottom hose hole 
> to
> see if the radiator appears blocked..
> 
>      I only use distilled water and
> coolant in my radiator.
>      Last year I put on a new Moss radiator cap and a
> new 185 thermostat and put on all new hoses.
>      My question is, why does it
> overheat after a long downhill? I could see it overheating after a long
> uphill.
>      Gotta get the temp gauge fixed. I meant to do it when the cold
> weather arrived.