The bypass hose bypasses both the heater and the radiator. There are
three parallel paths for the hot coolant back to the water pump inlet:
1. Through the heater valve and heater core;
2. Through the thermostat and radiator;
3. Through the bypass.
The radiator path is obviously the largest, although its ultimate flow
capability is limited by the actual thermostat opening area and the type
and condition of the radiator.
The heater path is dependent on the condition of the heater core, and on
whether or not you have the valve open (and how plugged the valve is ;)
The bypass path is the little right-angle elbow hose that comes off the
thermostat housing and goes straight back into the water pump inlet. If
there was no bypass at all (either from the heater, bypass, or bleed
holes on the thermostat) then the water pump would basically stall when
the thermostat was closed and there would be little or no coolant flow
at all in the engine, leading to localized boiling as well as retarding
the opening of the thermostat until things were way too hot. So you do
want the water to be circulating when the engine is cold... but once
it's warm, the bypass would ideally be minimized, so as to maximize the
flow through the radiators.
From: Tony Somebody [mailto:email@example.com]
Sent: January 25, 2010 11:12 AM
To: firstname.lastname@example.org; David and Varley Tweddle;
email@example.com; Smit, Theo
Subject: Re: [Tigers] Thanks to all for the great ideas. Re my
few unrelated questions email.
Theo- Ive always refered to the by pass as the "heater by pass hose".
So, am I correct in thinking when you plugged your by pass the heater no
longer would work if it was cold weather and I wanted heater on?
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