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Coolant. How to check correct temperature


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25 minutes ago, Lo100469 said:

there is no way to know what resistance they are cold and hot....

There are some resistance curves and cross-references in the document I linked to above. 

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I think I would like to try another gauge. Anyone have one, preferably known to read correctly, they are willing to let go?

Regards Richard 

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19 minutes ago, roy53 said:

Could the voltage stabiliser cause this ?

Yes it could but it would also make the fuel gauge read wrongly.  I asked about that in my first post on page 1 of the thread. 

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Ah yes i see that now.

In my case the fuel gauge is OK

Perhaps i just need to purchase every available type of sender as trial and error 

Roy

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You could do that but it might prove less frustrating to calibrate the gauge to suit a sender you already have.  The procedure for that is at the top of page 2. 

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I always wondered why "70C" degrees was mid-point on late (flat glass) TR4 gauges and "185F" on early (domed glass). No TR engine runs at 70C.

185F = 86C

158F = 70C

Did someone at Smiths-Jaeger have a typo-moment? Hence the fudged/ revised sender?

Anyway, my late gauge always read high until I got the correct, late sender. It now reads 70C bang-on. No need to calibrate gauge etc.

Yours conspiratorily

Adey

PS: great to see some of you at the International - It's been too long!

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6 hours ago, Ade-TR4 said:

Did someone at Smiths-Jaeger have a typo-moment? Hence the fudged/ revised sender?

It does look plausible but I think the real explanation is that the action of the bimetallic thermal-type temperature gauge is inherently non-linear as is the change in resistance of the type of sender used.  The combination of both in a simple instrument, as Smiths made them, naturally results in the scale becoming 'cramped' towards the hot end of the scale.  It could have been made to read more linearly but the cost would probably be disproportionate to the benefit.  Perhaps thats why most later cars don't have numbers - just C-N-H lettering. 

Of course the bourdon-tube gauges used in the early cars are more linear in response, but still not completely so.

 

 

Edited by RobH
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Interesting. I am looking for an early TR4 temp gauge (If my capillery one ever breaks, or, I have to remove the inner dash panel for any reason, then I will go electric tio save the hassle of feeding the capillery tube through ever again) The sort I am after has the same scale as the TR3 original.

494398603_TR4temp2.jpg.8adfc412b2be95aaf11d16e2e437fd28.jpg  895906498_TR4temp1.jpg.6cc8e66dc08e1d33121e144af0f3e036.jpg  1378679381_TR3Tempgauge.jpg.edfe98500dea017984ed1c6373caf585.jpg

Only difference I can see is the top end reads 250, and not 230

Bob

Edited by Lebro
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5 hours ago, Ade-TR4 said:

I always wondered why "70C" degrees was mid-point on late (flat glass) TR4 gauges and "185F" on early (domed glass). No TR engine runs at 70C.

185F = 86C

158F = 70C

Did someone at Smiths-Jaeger have a typo-moment? Hence the fudged/ revised sender?

Anyway, my late gauge always read high until I got the correct, late sender. It now reads 70C bang-on. No need to calibrate gauge etc.

Yours conspiratorily

Adey

PS: great to see some of you at the International - It's been too long!

The original bellows thermostat for summer use was rated to open 72 degrees c.   I used to run a 72 degree thermostat in the summer in my TR and the two things I noticed were cooler reading on the gauge when running and not such a hot heater.

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20 hours ago, RobH said:

You could do that but it might prove less frustrating to calibrate the gauge to suit a sender you already have.  The procedure for that is at the top of page 2. 

So i guess that i could first check the compatibility by taking out the sender and placing it in a known temp water. Leaving the gauge in place ?

Roy

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Yes. Don't forget you have to earth the body of the sender though. 

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11 hours ago, roy53 said:

Just checked and at 77c the gauge read 3/4  [ 7mm from hot ] so  i guess that means it's all ok

Now need to look at the rad .

Roy

Surely 77° should be halfway on the gauge as normal running temperatures or even a bit below? Or am I missing something 

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I thought that 100c would be just into the red H on the gauge.

But as Richmac has found his issue i will remove the gauge and adjust as Rob h post.

What temp should i see at half way ? in C please.

Roy

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I don't claim to be an expert, far from it but if you have an 82° C thermostat then it would ask for cooling at anything above and be shut anything below. So I am thinking 82°c should read half way on your gauge. Sure I'll be corrected if I'm wrong 

Edited by Richmac
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