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

Tue Mar 29 20:00:22 MDT 2022

Hi Bob -

the Robertshaw thermostats are nicely made, but they open the wrong way
around... let me do some measurements as I am dealing with the cooling on
my BJ8 now.  I have a robert shaw... as well as another sleeved thermostat
as well as the bellows.

Best,

Alan

On Wed, Mar 30, 2022 at 9:54 AM Bob Spidell <bspidell at comcast.net> wrote:

> 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 <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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