EPaul21988@aol.com wrote:
> Sam / John Haynes writes:
>> The paramount reason for
>> overheating in a TR2,3,4 is a non stock thermostat or no thermostat.
>> TeriAnn"s description of it is exactly correct. However I must disagree with
>> her statement "the longer the water is in contact with the radiator surface,
>> the more heat can be transfered. Without the restriction of the thermostat
>> slowing down the coolant flow , the coolent just may not have enough contact
>> time to transfer much heat." This statement conveys the mistaken idea that
>> by restricting the flow the engine will run cooler.
> I'm now lost on this one. You agree that one reason for overheating is the
> absence of a thermostat, but you disagree with the theory that the thermostat
> functions as a physical barrier to slow coolant down and allow more heat
> transfer ? Why does the absence of a thermostat result in overheating then
TR3s will tend to overheat without a thermostat, but the reason
that this happens isn't that the thermostat is slowing the
coolant down as it circulates through the cooling system.
The reason is that there is a "radiator bypass" in the TR3,
which is also controlled by the thermostat. If the thermostat
isn't present, much of the coolant runs round and round in
the engine, and never gets to the radiator -- correspondingly,
the car overheats. This is true for any car with a thermostat-
controlled radiator bypass.
TeriAnn mentioned this in her original post, but it got cut
somewhere along the line:
> A TR3 has a radiator bipass. This allows water to circulate
> within the engine while the thermostat is closed. This
> eliminates hot spots in the head that can lead to head cracks.
> The thermostat has a skirt that acts as a valve for the
> radiator bipass. When the thermostat opens, the skirt
> closes off the bipass. If you have the wrong thermostat
> or no thermostat in place close to half of the coolent will
> bipass the radiator and stay in the engine (guessed quantity
> based upon size of bipass hose and radiator
> rods).
For maximal cooling, one would block off the bypass port,
forcing all the coolant through the radiator, and run
without a thermostat. This would give maximum coolant
flow, without much of the coolant recirculating within
the engine, without ever getting to the radiator.
However, doing this would be unwise as it would make the
engine take significantly longer to warm up. If one is
having problems with overheating in a TR3, don't take the
thermostat out, but rather make sure that it is the correct
type to block off the radiator bypass, make sure that the
thermostat functions, and backflush the cooling system to
get rid of rust/scale which may be obstructing flow and
heat transfer. A stock TR3 cooling system in good condition
will keep the car from losing it's cool, even though it can
be marginal in hot days at idle, particularly with a poorly
tuned engine.
(I hope this isn't turning into a heated debate -- maybe
we all need a cooling off period... :-) )
--ken
'74 TR6 Daily Driver, well for at least 6 months each year...
--
Kenneth B. Streeter | EMAIL: streeter@sanders.com
Sanders, PTP2-A001 |
PO Box 868 | Voice: (603) 885-9604
Nashua, NH 03061 | Fax: (603) 885-0631
|