[Healeys] Coolant bypass port in the head - 6-cyl
Bob Spidell
bspidell at comcast.net
Tue Mar 29 19:49:13 MDT 2022
Years ago, someone--might have been BCS, but I'm not sure--was selling a
Robertshaw thermostat with a brass sleeve soldered to it (Robertshaw
thermostats have a center portion that moves up and down). The one I
bought was 160deg; I desoldered the sleeve and soldered it to a 180deg
Robertshaw. I bought one of the original, bellows-type from
Kees--whatever happened to him?--but never installed it; heard they were
the 'fail closed' type, which could turn a minor failure into a
catastrophe (still have it around somewhere).
https://flowkoolerwaterpumps.com/products/robertshaw-330-160-degree-thermostat
On 3/29/2022 6:35 PM, Alan Seigrist via Healeys wrote:
> 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 <mailto:healeys at autox.team.net>
> *Sent: *Tuesday, March 29, 2022 9:17 AM
> *To: *Healey list <mailto: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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