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</o:shapelayout></xml><![endif]--></head><body lang=EN-GB link=blue vlink=purple style='word-wrap:break-word'><div class=WordSection1><p class=MsoNormal><span style='mso-fareast-language:EN-US'>Alright so far. 25 years or so…………..<o:p></o:p></span></p><p class=MsoNormal><span style='mso-fareast-language:EN-US'><o:p> </o:p></span></p><div><div style='border:none;border-top:solid #E1E1E1 1.0pt;padding:3.0pt 0cm 0cm 0cm;font-size:pt'><p class=MsoNormal><b><span style='font-family:"Calibri",sans-serif'>From:</span></b><span style='font-family:"Calibri",sans-serif'> David Nock <healeydoc@sbcglobal.net> <br><b>Sent:</b> 19 September 2025 17:27<br><b>To:</b> Simon Lachlan <simon.lachlan@alexarevel.plus.com>; Harold Manifold <manifold@telus.net><br><b>Cc:</b> Richard Antal <rantal243@yahoo.com>; Healeys <healeys@autox.team.net><br><b>Subject:</b> Re: [Healeys] radiator thermostat<o:p></o:p></span></p></div></div><p class=MsoNormal><o:p> </o:p></p><p>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.<o:p></o:p></p><p><o:p> </o:p></p><p><o:p> </o:p></p><div><p class=MsoNormal>On 9/18/2025 1:15 PM, Simon Lachlan wrote:<o:p></o:p></p></div><blockquote style='margin-top:5.0pt;margin-bottom:5.0pt'><p class=MsoNormal>Hi, <o:p></o:p></p><div><p class=MsoNormal>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<o:p></o:p></p><div><p class=MsoNormal>Sent from my iPhone<o:p></o:p></p></div><div><p class=MsoNormal><br><br><o:p></o:p></p><blockquote style='margin-top:5.0pt;margin-bottom:5.0pt'><p class=MsoNormal style='margin-bottom:12.0pt'>On 18 Sep 2025, at 18:54, Harold Manifold <a href="mailto:manifold@telus.net"><manifold@telus.net></a> wrote:<o:p></o:p></p></blockquote></div><blockquote style='margin-top:5.0pt;margin-bottom:5.0pt'><div><p class=MsoNormal><span style='font-family:"Tahoma",sans-serif'></span> <o:p></o:p></p><div><div><p class=MsoNormal>Hi All,<o:p></o:p></p></div><div><p class=MsoNormal><o:p> </o:p></p></div><div><p class=MsoNormal>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.<o:p></o:p></p></div><div><p class=MsoNormal><o:p> </o:p></p></div><div><p class=MsoNormal>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.<o:p></o:p></p></div><div><p class=MsoNormal><o:p> </o:p></p></div><div><p class=MsoNormal>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.<o:p></o:p></p></div><div><p class=MsoNormal><o:p> </o:p></p></div><div><p class=MsoNormal>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.<o:p></o:p></p></div><div><p class=MsoNormal><o:p> </o:p></p></div><div><p class=MsoNormal>To add to the discussion, the engine fan has minimal effect at speeds greater than 15 miles per hour.<o:p></o:p></p></div><div><p class=MsoNormal><o:p> </o:p></p></div><div><p class=MsoNormal>Harold<o:p></o:p></p></div></div><p class=MsoNormal><o:p> </o:p></p><div><div><p class=MsoNormal>On Thu, Sep 18, 2025 at 8:46<span style='font-family:"Arial",sans-serif'> </span>AM David Nock via Healeys <<a href="mailto:healeys@autox.team.net">healeys@autox.team.net</a>> wrote:<o:p></o:p></p></div><blockquote style='border:none;border-left:solid #CCCCCC 1.0pt;padding:0cm 0cm 0cm 6.0pt;margin-left:4.8pt;margin-right:0cm'><div><p>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.<o:p></o:p></p><p>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. <o:p></o:p></p><p>David Nock<o:p></o:p></p><p>British Car Specialists<o:p></o:p></p><p><o:p> </o:p></p><div><p class=MsoNormal>On 9/17/2025 12:54 PM, Richard Mayor wrote:<o:p></o:p></p></div><blockquote style='margin-top:5.0pt;margin-bottom:5.0pt'><p class=MsoNormal>165 is too cold for good running. Our engines run better in the 180 to 190 range. <o:p></o:p></p><div><p class=MsoNormal> <o:p></o:p></p></div><div><p class=MsoNormal><o:p> </o:p></p><div><div><p class=MsoNormal>Sent from my iPad<o:p></o:p></p></div><div><p class=MsoNormal><br><br><o:p></o:p></p><blockquote style='margin-top:5.0pt;margin-bottom:5.0pt'><p class=MsoNormal style='margin-bottom:12.0pt'>On Sep 17, 2025, at 12:13<span style='font-family:"Arial",sans-serif'> </span>PM, Robert Markovich via Healeys <a href="mailto:healeys@autox.team.net" target="_blank"><healeys@autox.team.net></a> wrote:<o:p></o:p></p></blockquote></div><blockquote style='margin-top:5.0pt;margin-bottom:5.0pt'><div><p class=MsoNormal style='margin-bottom:12.0pt'><span style='font-family:"Tahoma",sans-serif'></span> 165 is the one I use<br><br><o:p></o:p></p><div><p class=MsoNormal><a href="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" target="_blank"><span style='font-size:9.0pt'>Sent from the all new AOL app for iOS</span></a><o:p></o:p></p></div><p class=MsoNormal><o:p> </o:p></p><p style='margin-top:0cm'><span style='font-size:11.5pt;color:#8473FF'>On Wednesday, September 17, 2025, 2:50 PM, Richard Antal via Healeys <a href="mailto:healeys@autox.team.net" target="_blank"><healeys@autox.team.net></a> wrote:<o:p></o:p></span></p><blockquote style='margin-top:5.0pt;margin-bottom:5.0pt'><div id="m_2673071501772592614yiv6324880639"><div><div><div><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Helvetica",sans-serif'>Gents,<o:p></o:p></span></p></div><div><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Helvetica",sans-serif'> 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.<o:p></o:p></span></p></div><div><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Helvetica",sans-serif'>rich antal<o:p></o:p></span></p></div></div></div></div><p class=MsoNormal style='margin-bottom:12.0pt'>_______________________________________________<br>Support Team.Net <a href="http://www.team.net/donate.html" target="_blank">http://www.team.net/donate.html</a><br>Suggested annual donation $12.75<br><br>Archive: <a href="http://www.team.net/pipermail/healeys" target="_blank">http://www.team.net/pipermail/healeys</a> <a href="http://autox.team.net/archive/healeys" target="_blank">http://autox.team.net/archive/healeys</a><br><br><a href="mailto:Healeys@autox.team.net" target="_blank">Healeys@autox.team.net</a><br><a href="http://autox.team.net/mailman/listinfo/healeys" target="_blank">http://autox.team.net/mailman/listinfo/healeys</a><br><br>Unsubscribe/Manage: <a href="http://autox.team.net/mailman/options/healeys/rmarkovich@aol.com" 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</o:p></pre><pre>Unsubscribe/Manage: <a href="http://autox.team.net/mailman/options/healeys/healeydoc@sbcglobalnet" target="_blank">http://autox.team.net/mailman/options/healeys/healeydoc@sbcglobal.net</a><o:p></o:p></pre><pre><o:p> </o:p></pre></blockquote><pre>-- <o:p></o:p></pre><pre>David Nock<o:p></o:p></pre><pre>British Car Specialists<o:p></o:p></pre><pre>Stockton Ca <o:p></o:p></pre><pre>209 948 8767<o:p></o:p></pre><pre><a href="http://www.britishcarspecialists.com" target="_blank">www.britishcarspecialists.com</a><o:p></o:p></pre></div><p class=MsoNormal style='margin-bottom:12.0pt'>_______________________________________________<br>Support Team.Net <a href="http://www.team.net/donate.html" target="_blank">http://www.team.net/donate.html</a><br>Suggested annual donation $12.75<br><br>Archive: <a href="http://www.team.net/pipermail/healeys" target="_blank">http://www.team.net/pipermail/healeys</a> <a href="http://autox.team.net/archive/healeys" target="_blank">http://autox.team.net/archive/healeys</a><br><br><a href="mailto:Healeys@autox.team.net" target="_blank">Healeys@autox.team.net</a><br><a href="http://autox.team.net/mailman/listinfo/healeys" target="_blank">http://autox.team.net/mailman/listinfo/healeys</a><br><br>Unsubscribe/Manage: <a href="http://autox.team.net/mailman/options/healeys/manifold@telus.net" target="_blank">http://autox.team.net/mailman/options/healeys/manifold@telus.net</a><o:p></o:p></p></blockquote></div><p class=MsoNormal style='margin-bottom:12.0pt'>_______________________________________________<br>Support Team.Net <a href="http://www.team.net/donate.html">http://www.team.net/donate.html</a><br>Suggested annual donation $12.75<br><br>Archive: <a href="http://www.team.net/pipermail/healeys">http://www.team.net/pipermail/healeys</a> <a href="http://autox.team.net/archive/healeys">http://autox.team.net/archive/healeys</a><br><br><a href="mailto:Healeys@autox.team.net">Healeys@autox.team.net</a><br><a href="http://autox.team.net/mailman/listinfo/healeys">http://autox.teamnet/mailman/listinfo/healeys</a><br><br>Unsubscribe/Manage: <a href="http://autox.team.net/mailman/options/healeys/simon.lachlan@alexarevel.plus.com">http://autox.team.net/mailman/options/healeys/simon.lachlan@alexarevel.plus.com</a><o:p></o:p></p></div></blockquote></div></blockquote><pre>-- <o:p></o:p></pre><pre>David Nock<o:p></o:p></pre><pre>British Car Specialists<o:p></o:p></pre><pre>Stockton Ca <o:p></o:p></pre><pre>209 948 8767<o:p></o:p></pre><pre><a href="http://www.britishcarspecialists.com">www.britishcarspecialists.com</a><o:p></o:p></pre></div></body></html>