[Fot] radiator preasure

[Randall]

> I have a problem with pressure in the radiator forcing coolant (water)
> to the overflow catch can but not allowing the coolant back in the
> radiator.

If it's not pulling coolant back out of the reservoir, then there is an air
leak somewhere.  Could be in the overflow hose, could be a water pump seal,
could be a small compression leak (too small to show on a compression test),
or (most common in my experience) the secondary seal in the radiator cap is
not sealing to the top of the radiator neck.

If you have an early TR4 with the tall (1") fill neck, most of the caps
available don't have that secondary seal.  Any radiator shop can substitute
a later neck, though.

Note that it is normal for a certain amount of water to be expelled to the
reservoir as the engine warms up.  Water expands more than cast iron does.
So the issue is why doesn't it get sucked back in as the engine cools.
Since it cools slowly, it only takes a microscopic leak to cause problems.

-- Randall