[Healeys] radiator thermostat

Wed Sep 17 20:53:57 MDT 2025

On my BJ8 I measure the coolant temp in the top hose.This is generally
about 10F less than the Smiths. I attribute this to the temp loss in the
hose ? Have calibrated this sensor with a mercury stick thermometer and it
is within a few degrees on the Smiths.  BTW hot coolant enters the rad.
from the top.
rg

On Wed, Sep 17, 2025 at 7:32 PM Michael Salter <michael.salter at gmail.com>
wrote:

> Something else to remember is that the temperature bulb is located either
> in the top tank of the radiator 100's & 100/6 or directly below the
> thermostat housing where the coolant which has passed through the radiator
> enters the engine. This means that the coolant in the engine and exiting
> from the engine is probably significantly hotter.
> Has anyone actually measured the temperature of the coolant as it enters
> the radiator at the bottom?
> It could well be that magic 185°F that an engine apparently requires for
> best operation occurs at a significantly lower indicated temperature.
>
> M
>
>
>
> ------------------------------
> *From:* Healeys <healeys-bounces at autox.team.net> on behalf of richard
> mayor <boyracer466 at gmail.com>
> *Sent:* Wednesday, September 17, 2025 7:09:14 PM
> *To:* Leach Hank <gradea1 at charter.net>
> *Cc:* Richard Antal <rantal243 at yahoo.com>; Healeys <healeys at autox.team.net
> >
> *Subject:* Re: [Healeys] radiator thermostat
>
> Hank makes a very good point about where to measure the water temp.  And
> to get an infrared temperature sensor.  I recently fired up a fresh V8
> engine to break in the cam.  I had also bought a new water temp gauge with
> sensor.  The new  sensor was screwed into a port on the cylinder head.  As
> we were running the engine I saw the temp climb and approach 220 degrees
> but fortunately I had my infrared sensor.  The water temp was actually
> quite lower and I was able to take readings from various places in the
> system.  If I had relied solely on the gauge I would have freaked out and
> probably shut the engine down.
>
> Just another example of the garbage that is being sold in the parts stores
> these days.
>
> Richard Mayor
> boyracer466 at gmail.com
>
>
>
> On Sep 17, 2025, at 3:47 PM, Hank Leach <gradea1 at charter.net> wrote:
>
> I would like to comment about the position of the temperature "sensor"
> found in the Healey. All of them-100s and 3000s measure the
> water/antifreeze temperature flowing thru the radiator. That is not
> necessarily the temperature of the engine itself. Using a heat detector gun
> (Harbor Freight) you can actually see the head, block and exhaust readings
> and they will be different than the degrees indicated which has been read
> in the water flowing and transferred down a long capillary tube to an
> analog gauge.
>
> In contrast, most older American cars, and incidentally the Jensen-Healey,
> measure the temperature of the manifold, or the block, by electronic sensor
> to an analog gauge.
>
> I'm sure todays' vehicles have more accurate measurements, but they don't
> tell us what that actual number is unless an icon illuminates on the dash
> indicating a problem with temperature. I guess that ancient type of
> measurement is what gives the Healey its charm. Be it Fahrenheit or
> Centigrade. Hank
>
> --------------------
>
> From: "Harold Manifold" <manifold at telus.net>
> To: "Richard Mayor" <boyracer466 at gmail.com>
> Cc: "Richard Antal" <rantal243 at yahoo.com>, "Healeys" <
> healeys at autox.team.net>
> Sent: September 17, 2025 at 3:05 PM PDT
> 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>
> 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> 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> 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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