[Healeys] radiator thermostat

[JSARCH]

Hi Herold,

 

I am puzzled by your statement that a thermostat can maintain a coolant temperature of + 20 degrees. Once a thermostat has opened at its set temperature, at least for our 1950’s engine technology, I believe the thermostat cannot regulate the coolant temperature unless the operating conditions of the engine are radically changed because the coolant temperature would be regulated by the air flow through the radiator. To put it another way, once the thermostat is fully open the coolant temperature is regulated by the radiator, if the thermostat were to close the coolant temperature would be regulated by the engine temperature which could only be higher because of the combustion temperatures. 

 

John

 

From: Healeys <healeys-bounces at autox.team.net> On Behalf Of Harold Manifold
Sent: Wednesday, September 17, 2025 1:52 PM
To: Richard Mayor <boyracer466 at gmail.com>
Cc: Richard Antal <rantal243 at yahoo.com>; Healeys <healeys at autox.team.net>
Subject: Re: [Healeys] radiator thermostat

 

Hi All,

 

Thermostats always generate interesting discussions.

 

I use a 180-degree thermostat in my car. However, what's equally important is how effectively the thermostat regulates the coolant temperature. A thermostat that is fully closed or fully open is no longer actively controlling the temperature. The normal operating range is typically the opening temperature plus 20 degrees. For example, a 165-degree thermostat should maintain the temperature between 165 and 185 degrees, while a 180-degree thermostat should keep it between 180 and 200 degrees.

 

If your current thermostat maintains the coolant temperature within its specified range under normal driving conditions, then it's the correct one for your needs.

 

Harold

 

On Wed, Sep 17, 2025 at 1:36 PM Richard Mayor <boyracer466 at gmail.com <mailto:boyracer466 at gmail.com> > 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



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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

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