[Healeys] Coolant bypass port in the head - 6-cyl
Bob Spidell
bspidell at comcast.net
Tue Mar 29 20:09:36 MDT 2022
It's been years, and my memory is (always) suspect, but I believe I put
a RS in a pan of boiling water (with a frog, of course). The conical top
of the RS goes up in the thermostat housing, so I think the moving part
can only go down. IIRC, the sleeve only moved a quarter-inch or so and I
thought at the time it would only cover maybe half of the bypass port.
I mostly came to the conclusion Michael did: Covering the port or not
makes no measurable difference; it's certainly not a cure for
overheating Healeys.
On another note; I drained my BJ8 to install another heater valve and
block valve and, when filling noticed some crud blocking a couple tubes.
It was hard to extract, but when I did it appeared to be solder that had
come off from somewher (by the shape probably from around a tube). Rad's
not leaking, but I'm not a happy camper; this was an 'uprated' core
installed less than 6 or 7 years ago.
On 3/29/2022 7:00 PM, Alan Seigrist wrote:
> 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
>> <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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