I can't disagree with simply "restricting" the coolant flow rather than
blocking it off completely. It's just that I have been running that way for
years with only other non-bypass issues giving me problems.
I only relate what has worked for me here in Minne"snow"ta.
Regards,
Lew Palmer
-----Original Message-----
From: Larry Cogan [mailto:woodrat@spacey.net]
Sent: Thursday, July 06, 2000 4:12 PM
To: Lew Palmer; Stuart Keen; MG T Digest
Subject: Re: Thermostat
Lew: Im not an expert on this, for sure, but let me relay the essence
of whats been a recent long thread on the T-ABC list. (Of course the
XPAG engine is the same in the TC.) Some very smart guys have made
the point that blocking off the by pass completely is not good, if a
thermostat is installed. The reason has to do with localized hot
spots at the rear of the engine which develop because if the bypass
is totally blocked, there is no coolant movement for a period of time
before the thermostat opens. The consesus is to place a restrictor
plate in the bypass with a 3/8" hole in the plate. This then of
course allows some movement of coolant to take place while waiting for
the thermostat. Additionally, if the thermostat fails closed, you
have a much more "benign" temp rise, hopefully allowing you to see the
problem before meltdown.
Leave it wide open or put in a drilled plate. Regards, Larry
----- Original Message -----
From: Lew Palmer <lpalmer@mn.mediaone.net>
To: Stuart Keen <simbafish@home.com>; MG T Digest
<mg-t@autox.team.net>
Sent: Thursday, July 06, 2000 4:22 PM
Subject: RE: Thermostat
> Stu,
>
> Although Minnesota isn't exactly Florida climate, we do a lot of
touring in
> the hot summer months (90 degrees). Here's what I do:
>
> 1) I completely block off the bypass. I simply cut a solid gasket
from a
> plastic pop bottle and place between the thermostat housing and the
bypass
> elbow.
>
> 2) I make sure all water passages in the block and radiator are
clear.
> Especially prone to blockage are the areas behind the
expansion/access plugs
> in the block.
>
> 3) I make sure I have the minimum possible amount of clearance
between the
> water pump impellor and pump body.
>
> 2) I add 1 quart of NAPAKool to the radiator into a 50% mixture of
> water/antifreeze. (A lower ratio is better (more water than
antifreeze), but
> unless I want to constantly change mixtures during the year, I can't
because
> of freezing temperatures during the cold months.)
>
> 3) I drive with no concerns.
>
> I am only using a stock, modern thrmostat (don't remember the
number, but it
> is a 165 degree unit) that fits the opening.
>
> And, yes, water flows from the engine into the top of the radiator
and out
> the bottom. (Remember, hot water rises, cold water sinks). This
gives an
> assist to the water pump because of thermosyphon action. Many
pre-war MGs
> never even used a water pump, relying solely on thermosyphonic
action.
>
> Regards,
> Lew Palmer
>
> -----Original Message-----
> From: owner-mg-t@autox.team.net [mailto:owner-mg-t@autox.team.net]On
> Behalf Of Stuart Keen
> Sent: Thursday, July 06, 2000 2:54 PM
> To: MG T Digest
> Subject: Thermostat
>
>
> The original thermostat in my 1951 MGTD MKII is defective and a
similar
> type is no longer available. What should I do? Please bare with me
as I
> explain in somewhat detail; history and what has been done to date.
>
> When I purchased the TD, the thermostat was the removable type, it
had a
> center brass bolt which bolted to a cross arm in the upper parts of
the
> housing. The bolt was affixed to 1) a 1 7/8 inch diameter, 5/8 inch
high
> brass band (which affected the flow in the bypass tube) and 2) to
the
> thermostat diaphragm. The bottom of the diaphragm was bolted to a 2
inch
> diameter flat ring via three supporting arms. This lower ring fitted
> into a grove in the housing. To install, the thermostat was inserted
> through the bottom of the housing until seated and the top bolt was
> inserted in the crossarm and the nut tightened.
>
> The thermostat was inoperative when I purchased the car. The
previous
> owner had soldered the diaphragm in the compressed (open) condition,
> saying that driving in Florida, the thermostat would be open all the
> time anyway. He emphasised the need for some restriction in the
water
> flow path.
>
> When the engine was rebuilt in January, the machine shop saw the
> soldered thermostat and junked it; ie. returned the TD with no
> thermostat installed. I have the old thermostat but it is in pieces;
i.e
> butchered.
>
> Being advised I should not drive the TD without a restriction in the
> water flow, I ordered a thermostat from Moss (also tried Abingdon,
but
> they had none available). The Moss thermostat was completely
different,
> just a flat circular plate with a small thermostat system protruding
> from the center. The replacement fit loosely in the grove in the
bottom
> of the thermostat housing, so I flattened the raised edge to make it
> more snug.
>
> I am concerned about the thermostat since I am about to make a 5,000
> mile trip in the TD. I was about to order a housing with
non-removable
> thermostat from Moss, but would like advice first to know if this
> expense is really necessary.
>
> Last night I read over 200 archived messages about thermostats. The
> common thread is that you should have some restriction in the bypass
> outlet. The original unit provided this with the brass band, but the
> Moss replacement does not provide any restriction. Is control of the
> bypass really necessary if I am driving in a hot climate all year?
>
> I ask if it is really necessary because I have now driven approx
4,000
> miles with the Moss replacement thermostat installed and with no
> restriction in the bypass outlet. Much of the driving has been in
> Florida, but even here my water temperature gauge (rebuilt several
> months ago by MoMa) never registers higher than 83 deg C, usually in
the
> mid to high 70s. The water temperature seems to be okay, so should I
> even be worrying about the quasi thermostat installation in my TD.
Am I
> just being a perfectionist and a worry wart?
>
> I am not even sure I installed the replacement thermostat correctly,
but
> it seems to work. The unit is marked with the words "TOP" on the
ring,
> with the spring and housing protruding below. This is how I have it
> installed. However, there is an annotation on the side saying "Flow"
and
> an upward arrow. What is the direction of water in the system? Is
water
> coming from the top of the engine, UP into the thermostat housing
and
> then into the top of the radiator to cycle downward and be cooled.
For
> some reason I thought it was the reverse. Shows how little I know
about
> cars.
>
> I am listening to all advice, such as
>
> 1) leave well enough alone, the water temperature seems to be okay
now
>
> 2) order a housing with non removable thermostat from Moss
>
> 3) put some kind of restriction across the bypass opening as
suggested
> by some of the archives.
>
> Thanks for your patience in reading all this detail, for putting my
mind
> at ease and for any suggestions.
>
> Stu Keen
> Venice, Fl
> simbafish@home.com
>
>
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