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

Wed Mar 30 15:28:38 MDT 2022

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
>
>
>
> *From: *Michael Salter via Healeys <healeys at autox.team.net>
> *Sent: *Tuesday, March 29, 2022 9:17 AM
> *To: *Healey list <Healeys at autox.team.net>
> *Subject: *Re: [Healeys] Coolant bypass port in the head - 6-cyl
>
>
>
> The coolant travels from the bottom of the radiator to the water pump into
> the block then from the block into the head then through the thermostat to
> the top of the radiator.
>
>
>
> M
>
>
>
> On Tue., Mar. 29, 2022, 11:57 a.m. Elton S, <eps2660 at gmail.com> wrote:
>
> As a related question, what is the direction of flow through the radiator
> - up from the bottom or down from the top?
>
> Elton
>
> BJ7
>
>
>
> On Tue, Mar 29, 2022 at 11:44 AM Michael Salter <michaelsalter at gmail.com>
> wrote:
>
> As Gary points out, and far as I have been able to figure out, the bypass
> passage is open when the engine is cold, the idea being that by "short
> circuiting" the radiator the coolant in the heater and bypass passage will
> warm up more quickly and the heater will produce heat more quickly.
>
> We had a slew of the "shrouded " type thermostats that I bought when
> Smiths Canada closed down. The part number was 43570/28 and we used to sell
> them to customers who reported overheating problems.
>
> I stopped promoting them as a potential solution to overheating issues
> after being taken to task by a customer who did an extensive study of the
> issue and proved, at least to my satisfaction,  that they improved cooling
> not one iota.
>
>
>
> M
>
>
>
> On Tue., Mar. 29, 2022, 10:47 a.m. Alan Seigrist, <healey.nut at gmail.com>
> wrote:
>
> I don't know if this has ever been answered before, but where does the
> little bypass port begin?
>
>
>
> What parts of the head does that bypass come in contact with?
>
> When do you want to cover the port with a sleeve (when coolant is hot or
> cold?)
>
>
>
> I ask because the old bellows style thermostat will cover the bypass port
> when the thermostat opens
>
> then I have another wax thermostat and the sleeve actually cover the
> bypass when it is cold, and doesn't cover it when the thermostat opens....
> so it works exact opposite to the old bellows style thermostat.
>
>
>
> confused....
>
> Cheers,
>
>
>
> Alan
>
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