[Healeys] Coolant bypass port in the head - 6-cyl

Wed Mar 30 19:34:38 MDT 2022

Harold -

Thank you, that is great information.  Oddly I have a purchased unit that
is exactly as you show on the right.  Must be Moss or someone made that
same modification.  Generally speaking I think these sleeved thermostats
only really matter for hot climates... probably for cooler climates, a
normal thermostat is good enough.

Best,

Alan

On Thu, Mar 31, 2022 at 8:10 AM Harold Manifold via Healeys <
healeys at autox.team.net> wrote:

> The blanking sleeve was available for Healey’s and is listed in the parts
> list with this note: “Sleeve - thermostat blanking               11G 176 b
> For use in extremely hot climates in lieu of thermostat, optional extra”. I
> don’t think it is a good idea to use the blanking sleeve and a thermostat.
> The blanking sleeve will fit any car that uses a standard 2 1/8” thermostat.
>
>
>
> Pictures of the modified Land Rover 596225 thermostat are attached. Remove
> the upper lip from the original thermostat with a Dremel cutting disk. The
> material is soft brass and cuts easily. The original in the open and closed
> position is on the left and the modified is on the right. The other picture
> is the modified thermostat in a Healey 3000 cylinder head.
>
>
>
> Harold
>
>
>
> *From: *Mark Donaldson <ardmorebusiness at xtra.co.nz>
> *Sent: *Wednesday, March 30, 2022 3:16 PM
> *To: *Jim Ryan <ryan at jimryan.com>
> *Cc: *Harold Manifold <manifold at telus.net>; Healey list
> <Healeys at autox.team.net>
> *Subject: *RE: [Healeys] Coolant bypass port in the head - 6-cyl
>
>
>
> Jim,
>
>
>
> I never experienced overheating in our 997 Austin-Cooper. The sleeve fits
> many Minis, so I am sure it will fit you’re ‘A’ series engine too.
>
>
>
> The image below incorrectly says it fits a Hundred.  Clearly it does not.
> But it DOES say it fits a *Sprite*.
>
>
>
> Cheers
>
> Mark
>
>
>
>
>
>
>
>
>
> *From:* Jim Ryan <ryan at jimryan.com>
> *Sent:* Thursday, 31 March 2022 10:29 AM
> *To:* Mark Donaldson <ardmorebusiness at xtra.co.nz>
> *Cc:* Harold Manifold <manifold at telus.net>; Healey list <
> Healeys at autox.team.net>
> *Subject:* Re: [Healeys] Coolant bypass port in the head - 6-cyl
>
>
>
> I've been following this, and just wondered if any of this would apply to
> a bugeye with the stock 948 in it.
>
>
>
> On Wed, Mar 30, 2022, 4:33 PM Mark Donaldson via Healeys <
> healeys at autox.team.net> wrote:
>
> Gentlemen,
>
>
>
> I had ongoing mild occasional overheating issues in my 3000 tri-carb for
> many years  . . .  until I fitted a *blanking sleeve* two years ago.
>
> Problem instantly solved.  It’ll sometimes climb to 190 on a high-speed
> hill climb but, otherwise, rock steady where it should be.
>
>
>
> The sleeve is a stock BMC part.  I got mine from a local Mini supply house
> here in NZ.  The part number is  *11G 176*.
>
> Moss sells them: 434-135.     I know other suppliers do also.
>
>
>
> I fit it with a wax stat, which sits neatly on top.
>
>
>
> Mark
>
> Ardmore
>
> NZ
>
>
>
> *From:* Alan Seigrist <healey.nut at gmail.com>
> *Sent:* Wednesday, 30 March 2022 2:36 PM
> *To:* Harold Manifold <manifold at telus.net>
> *Cc:* Michael Salter <michaelsalter at gmail.com>; Healey list <
> Healeys at autox.team.net>
> *Subject:* Re: [Healeys] Coolant bypass port in the head - 6-cyl
>
>
>
> Harold -
>
>
>
> Thank you, now I understand how the whole thing is supposed to work.  The
> sleeve works to cut off the bypass so that hot water is not recycled into
> the system after it warms up.  FWIW, this only applies to the 6 cyl, the 4
> cyl doesn't have any sort of bypass.
>
> Yes, I think it would be great if you could share with us which thermostat
> to purchase and how to modify it.
>
> Best,
>
> Alan
>
>
>
> On Wed, Mar 30, 2022 at 1:28 AM Harold Manifold via Healeys <
> healeys at autox.team.net> wrote:
>
> The coolant bypass plays an important but problematic role in the Healey’s
> cooling system. When the thermostat is closed coolant returns to the water
> pump via the bypass. See the red circle on the attached picture. The bypass
> is important for three reasons: its allows the coolant in the block to
> continue to circulate and come to a uniform temperature before the
> thermostat opens, it prevents hot spots that could develop from stagnant
> coolant and it prevents the water pump from dead heading.
>
> The problematic part is in the original design the bypass was closed by a
> sleeve on the bellows type thermostat when the thermostat opened. The
> original Bellows type thermostat used a volatile liquid and were not
> reliable and were not suitable for the 7 psi cooling system pressure. Wax
> type thermostats are much more reliable but they do not have a sleeve to
> close off the bypass. There may be some expensive wax type replicas of the
> original bellows type.
>
> After looking at many options the best option for a reasonably priced wax
> type thermostat with a sleeve to close off the bay pass is the modified
> Land Rover Series ll thermostat. If anyone would like to know about
> modifying the Landver thermostat let me know. It can be easily done.
>
> Harold
>
>
>
>
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