[DeTomaso] Heater control valve

[Larry Finch]

 Barry wrote-

 
Just a note of caution on this:

The only benefit to allowing any portion of the coolant to bypass the rad
and return to the engine directly, is when the engine is cold. Once it's hot
outdoors, allowing "constant water flow back to the engine" actually impacts
negatively on the engine cooling system, moving in the direction of
overheating.


"The water is continuously flowing through the heater hose and does not stop
the flow like the original valve did."

In fact, the original valve helps to add capacity to the cooling system by
stopping the bypass of coolant in hot weather (if it's working).

These things matter in a mid-engine car with marginal cooling system? Of
course, manual shutoff valves would stop this loss by bypass too.

Barry

-----------

Barry, I think you are confusing two aspects of the coolant system in a Pantera.
And perhaps confusing the job of a thermostat and the heater core shut-off valve?

We often discuss the problem created when a stock 351C uses a Windsor thermostat.
The Windsor stat will allow some coolant to always bypass its proper flow through the radiator,
instead it is allowed to flow back to the engine block. This happens because the Windsor stat does
not have a 'hat' that expands when warm to block the engine bypass passage. Allowing some coolant to
bypass the radiator is what the 351C stat allows, but only to assist in engine warm-up.
At that point the 351C stat closes the "hat", blocking the bypass passage and forcing
all coolant to travel through the radiator.

The 4-port valve in question is connected to the supply and return hoses for ONLY the
heater core. It is NOT part of the radiator coolant piping.

In a stock Pantera, the dash heater valve just "dead heads' the coolant flow at the valve.
The water pump is still trying to push coolant through the hose, but the flow is blocked.
This restriction to letting the water pump work is likely not advisable. It may in fact
affect coolant flow in not just the heater hoses, but also the radiator portion. I've never
really seen that possibility fully discussed or analyzed.

The advantage of the 4-port valve with the bypass function is the flow of coolant pushed
by the water pump into the hose feeding the heater core is not blocked, but is free to return
(via the heater core return hose) to the engine block. As I conjectured above, this MAY in
fact improve flow of coolant to the radiator.

If one digests all the info I've posted in the POCA album, one sees the 4-port valve does allow a small
coolant flow through the heater core EVEN when 'closed'. Likewise, it also allows a small amount
to bypass the heater core even when fully open. The manufacturer rep I spoke with agreed with me
that this may have been incorporated in the design specs to prevent the stagnation (and possible
corrosive results) of coolant trapped in a heater core all summer long.

I'm now taking that same thinking and wondering if Ford perhaps intended our heater core valves to
NOT fully close for the same reasoning. Problem being, the AC portion is so minimal, that small hot
coolant flow during summer seriously degrades the ability of the AC to provide low temp cabin air.

Perhaps another owner with other-vehicle knowledge can address the question of other car heater
systems and whether those valves FULLY close?

The two manual shut-off valves many of us install act like the stock under-dash heater core valve -
they 'dead head' the coolant flow in the heater hoses. They are also a PITA to open/close as weather
requires, as I wrote regarding my yearly Monterey experiences.

The use of the 4-port valve can in no way adversely affect the engine's cooling abilities, any more 
than the stock under-dash valve or our added shut-off valves would do.

Larry