Not sure about specific MMM issues, but generally there should be a bypass
of some sort to allow some flow even when the thermostat is shut, to prevent
hotspots occuring before the thermostat opens. In the A-Series engine
(Spridgets etc) there was a small hose under the water pump that did this,
the later (A+) engines did not have this bypass hose but had heaters that
always took some flow. My (Turbocharged) Sprite has this set-up and all is
well.
One other issue with putting the thermostat in the hose is it might not
recieve any heat to open it, even if the water in the engine is already too
hot, unless there is some flow of water past it. In Vizards A-Series tuning
book he suggests drilling a couple of holes in the thermostat base plate to
provide the bypass flow path - maybe this would be worthwhile for the MMM
application.
My other thought is regarding non-pumped systems. Would the thermostst in
the top hose give too much restriction for thermosyphoning to be effective
enough?
Neil
PA1218
'68 CGT, '73 Midget, '71 Sprite Turbo
----- Original Message -----
From: "Gill And Dick Morbey" <gd.morbey@virgin.net>
To: <mg-mmm@autox.team.net>
Sent: Friday, January 03, 2003 11:49 PM
Subject: Thermostat in PA cooling system. Worth the effort?
> Dear All,
>
> (The following is a repeat of a message I tried to circulate recently - it
> appeared to go into a black cyber hole!)
>
> The excellent Triple M Bulletin bulletin, edited by Philip Bayne-Powell,
is a
> fascinating and regular publication available to Triple M register
members.
>
> In the latest one I spotted a tip which may be of help to us Brits at this
> time of year - fit a thermostat into the top hose. Halfords evidently
sell
> one that is a nice snug fit. It is their part no. HTS 610.
>
> This set me wondering.
>
> The Halfords thermostat is of a type which remains totally closed until
the
> temperature rises to 83 degrees C, whereupon it opens. It has no bleed
hole
> or bypass valve.
>
> My P type has a water pump fitted, which circulates water away from the
botom
> of the radiator and assists its flow through the hot part of the engine
until
> it reaches the rad header tank. In normal conditions this allows the
engine
> to run cool - far too cool, I suspect - 60 degrees in Winter and not much
> above 75 degrees in Summer. Blanking the bottom of the rad has helped to
get
> a bit of extra heat into the system, but not much!
>
> So, if I fit a thermostat, I reckon that the water will heat up nicely,
but
> will have nowhere to go until the temperature reaches 83 degrees and the
> thermo valve opens. So instead of being over-cooled, it's likely that the
> beastie may become over-heated - es[ecialy at the back end of the cylinder
> head !
>
> What opinions do MMM folks have on this subject. And would it be any
> different for cars that do not have a water pump, and simply rely on
> thermo-syphoning to move the water around?
>
> Best wishes to all.
> Dick Morbey
> PA 0743
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