[Healeys] radiator thermostat

David Nock healeydoc at sbcglobal.net
Fri Sep 19 10:27:21 MDT 2025 

If you are using the original style Bellow thermostat be sure that you 
DO NOT use a higher pressure radiator cap. If you run a bellow 
thermostat and a higher pressure cap the excess pressure will close the 
thermostat once the cooling system gets up to temperature. Causing the 
engine to overheat.



On 9/18/2025 1:15 PM, Simon Lachlan wrote:
> Hi,
> The original sleeved ones are - I think - easier to find in the UK. 
> Certainly, I managed to find a few. I was advised that the Morgan 
> people were a good source. I bought mine on eBay but that was a while 
> ago. Simon
> Sent from my iPhone
>
>> On 18 Sep 2025, at 18:54, Harold Manifold <manifold at telus.net> wrote:
>>
>> 
>> Hi All,
>>
>> Thermostats and Healey cooling always generate interesting 
>> discussions, and I'd like to clarify my previous comments on what 
>> controls (or often doesn't control) the coolant temperature.
>>
>> To summarize some of the points made: Coolant flows down the 
>> radiator, out the bottom hose, and into the water pump. It's then 
>> pumped into the engine block's cooling jacket. The goal is to direct 
>> the coolest fluid to the hottest part of the engine for optimal heat 
>> transfer (i.e., the largest delta T). The coolant, having absorbed 
>> heat, then moves up to the cylinder head, through the thermostat, and 
>> back to the radiator. This process is known as thermosiphoning, where 
>> heated coolant rises through the engine and falls as it cools in the 
>> radiator.
>>
>> The heat generated by the engine is a function of the combustion 
>> process (timing, carburation, etc.) and horsepower efficiency loss. 
>> More horsepower output means more heat transferred to the coolant. 
>> The radiator removes this heat, but its effectiveness is proportional 
>> to the difference between the air and coolant temperatures.
>>
>> Assuming the radiator has sufficient capacity to remove heat, if the 
>> coolant temperature the thermostat "sees" is less than its opening 
>> temperature plus 20 degrees, the thermostat will slightly close to 
>> restrict flow to the radiator. In this scenario, the thermostat is 
>> actively controlling the coolant temperature. However, if the coolant 
>> temperature exceeds 20 degrees above the thermostat's opening 
>> temperature, then the coolant temperature is primarily a function of 
>> the incoming air temperature, and the thermostat is no longer a 
>> factor. In such cases, the coolant temperature is effectively 
>> uncontrolled by the thermostat.
>>
>> To add to the discussion, the engine fan has minimal effect at speeds 
>> greater than 15 miles per hour.
>>
>> Harold
>>
>> On Thu, Sep 18, 2025 at 8:46 AM David Nock via Healeys 
>> <healeys at autox.team.net> wrote:
>>
>>     The thermostat does not control the high end temperature of the
>>     engine. Its job is to get the engine up to an operating
>>     temperature as soon as possible. Then in maintains the low end
>>     temperature of the engine. Once the thermostat is open the engine
>>     temperature is controlled by the radiator, radiator fan and air flow.
>>
>>     On the 6 cylinder engine there is a sleeve attached to the
>>     thermostat, that blocks off a bypass in the cylinder head. The
>>     bypass is there to allow the coolant to flow when the thermostat
>>     is closed. Once the thermostat is open the sleeve is there to
>>     block the bypass allowing ALL the coolant to flow thru the radiator.
>>
>>     David Nock
>>
>>     British Car Specialists
>>
>>
>>     On 9/17/2025 12:54 PM, Richard Mayor wrote:
>>>     165 is too cold for good running.  Our engines run better in the
>>>     180 to 190 range.
>>>
>>>     Sent from my iPad
>>>
>>>>     On Sep 17, 2025, at 12:13 PM, Robert Markovich via Healeys
>>>>     <healeys at autox.team.net> <mailto:healeys at autox.team.net> wrote:
>>>>
>>>>      165 is the one I use
>>>>
>>>>
>>>>     Sent from the all new AOL app for iOS
>>>>     <https://aolapp.onelink.me/eG2g?pid=NativePlacement&c=US_Acquisition_YMktg_320_EmailSignature_AttributionDL&af_sub1=Acquisition&af_sub2=US_YMktg&af_sub3=&af_sub4=100002473&af_sub5=SentFromNewAOLApp__Interstitial_&af_ios_store_cpp=ce85ce34-ad0f-4811-a92b-a172743b064e&af_android_url=https%3A%2F%2Fplay.google.com%2Fstore%2Fapps%2Fdetails%3Fid%3Dcom.aol.mobile.aolapp%26listing%3Demail_signature_attribution>
>>>>
>>>>     On Wednesday, September 17, 2025, 2:50 PM, Richard Antal via
>>>>     Healeys <healeys at autox.team.net>
>>>>     <mailto:healeys at autox.team.net> wrote:
>>>>
>>>>         Gents,
>>>>              What is the desired coolant temperature for optimal
>>>>         engine performance? I've searched the tech articles and can
>>>>         find nothing that specifically answers that question. This
>>>>         summer my BJ8 seemed to run fine with a 160 thermostat
>>>>         which, according to the gauge which I've checked and found
>>>>         to be accurate, kept the coolant at around 165. Thanks to
>>>>         all who respond.
>>>>         rich antal
>>>>         _______________________________________________
>>>>         Support Team.Net http://www.team.net/donate.html
>>>>         Suggested annual donation  $12.75
>>>>
>>>>         Archive: http://www.team.net/pipermail/healeys
>>>>         http://autox.team.net/archive/healeys
>>>>
>>>>         Healeys at autox.team.net
>>>>         http://autox.team.net/mailman/listinfo/healeys
>>>>
>>>>         Unsubscribe/Manage:
>>>>         http://autox.team.net/mailman/options/healeys/rmarkovich@aol.com
>>>>
>>>>     _______________________________________________
>>>>     Support Team.Net http://www.team.net/donate.html
>>>>     Suggested annual donation  $12.75
>>>>
>>>>     Archive: http://www.team.net/pipermail/healeys
>>>>     http://autox.team.net/archive/healeys
>>>>
>>>>     Healeys at autox.team.net
>>>>     http://autox.team.net/mailman/listinfo/healeys
>>>>
>>>>     Unsubscribe/Manage:
>>>>     http://autox.team.net/mailman/options/healeys/boyracer466@gmail.com
>>>>
>>>
>>>     _______________________________________________
>>>     Support Team.Nethttp://www.team.net/donate.html
>>>     Suggested annual donation  $12.75
>>>
>>>     Archive:http://www.team.net/pipermail/healeys http://autox.team.net/archive/healeys
>>>
>>>     Healeys at autox.team.net
>>>     http://autox.team.net/mailman/listinfo/healeys
>>>
>>>     Unsubscribe/Manage:http://autox.team.net/mailman/options/healeys/healeydoc@sbcglobal.net
>>>
>>     -- 
>>     David Nock
>>     British Car Specialists
>>     Stockton Ca
>>     209 948 8767
>>     www.britishcarspecialists.com <http://www.britishcarspecialists.com>
>>
>>     _______________________________________________
>>     Support Team.Net http://www.team.net/donate.html
>>     Suggested annual donation  $12.75
>>
>>     Archive: http://www.team.net/pipermail/healeys
>>     http://autox.team.net/archive/healeys
>>
>>     Healeys at autox.team.net
>>     http://autox.team.net/mailman/listinfo/healeys
>>
>>     Unsubscribe/Manage:
>>     http://autox.team.net/mailman/options/healeys/manifold@telus.net
>>
>> _______________________________________________
>> Support Team.Net http://www.team.net/donate.html
>> Suggested annual donation  $12.75
>>
>> Archive: http://www.team.net/pipermail/healeys 
>> http://autox.team.net/archive/healeys
>>
>> Healeys at autox.team.net
>> http://autox.team.net/mailman/listinfo/healeys
>>
>> Unsubscribe/Manage: 
>> http://autox.team.net/mailman/options/healeys/simon.lachlan@alexarevel.plus.com
>>
-- 
David Nock
British Car Specialists
Stockton Ca
209 948 8767
www.britishcarspecialists.com
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://autox.team.net/pipermail/healeys/attachments/20250919/64831715/attachment.htm>

More information about the Healeys mailing list