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When operating on the highway today in TX my engine temp gauge was at about 5/8. Is that normal?

SF Roth

I think the gauge should normally show more like 3/8ths i.e. just below the mid point, rather than just above. But individual cars vary - is 5/8ths higher than you are used to seeing?

Was this sitting in traffic, or were you on the move? Standard cooling system & fan, or any modifications?

Tony

<font size="1">1981 TR7 FHC Cavalry Blue
1980 TR7V8 DHC Jaguar Regency Red - sadly sold!
1977 TR8 FHC EFI Factory development car Inca Yellow</font id="size1">

My good friend Sean, does there reside in your diagnostic tool bucket a temperature gun? If not, then why?

So, after trotting down to your local Harbor Freight tool store to purchase one, you will be enjoying aiming it at the top of the thermostat housing of your completely warmed up TR7 that you drove to get the temperature gun.

What is the temperature of the hot thermostat housing?

If the temperature is about 180 degrees F., the temperature gauge in the car should read just below the half way mark. If the temperature is about 190 degrees F., the gauge reading should be just over the halfway mark.

Please note, due to the U.S. E.P.A. emissions mandate back in the 1970's, the factory installed 190 degree thermostats in our engines to increase the combustion temperatures to get a smidgen more power out of the detuned engines. This was not a good idea due to the marginal reliability of the head design and on the early engines, the presence of that nylon filler plug on top of the thermostat housing. That plug had a tendency to pop the cork releasing all the hot coolant and warping the head. This is why the TR7 community has installed 180 degree units instead.

There are other items to be discussed, but they can wait till later.

Mildred Hargis

Hi, no mods. It is usually a needle width higher than half on the temp gauge. Yesterday it was two needle widths higher, that was on the highway doing 70mph for about 45 miles.

After I got off it cooled back to normal mid gauge range.

SF Roth

Okay, let's review your driving environment. You live in southeast Texas, it's July, it's hot & humid, you're driving on a blacktop highway with a radiant heat in the area of 125 degrees F., and you're spinning the engine at about 3000 RPM.

Is that about it?

So, you've got 125 degree F. hot air from the pavement being drawn thru the radiator with a thermostatically controlled heated coolant of about 180 degrees, depending on the thermostat in the housing. The temperature gauge reads at and over 1/2. Is the engine safe?

Well, yes it is. However, more questions need to be asked. Are both of the side boards next to the radiator intact? What is the rating of the thermostat? Are the radiator fins clear of road debris to allow sufficient air flow? Is the radiator flowing coolant thru all the tubes?

When these questions have been answered, a better assessment of your original query can be made.

Mildred Hargis

<blockquote id="quote"><font size="1" face="Century Gothic, Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by Sean Roth</i>

Hi, no mods. It is usually a needle width higher than half on the temp gauge. Yesterday it was two needle widths higher, that was on the highway doing 70mph for about 45 miles.

After I got off it cooled back to normal mid gauge range.
<hr height="1" noshade id="quote"></font id="quote"></blockquote id="quote">

That's about right. When it's cooler the gauge sits at just over a quarter (where the thermostat limits the amount of coolant entering the cooling system) and when it's hot out (it's hitting 80F these days, just like in California only better [8D]) the needle will go up a needle width maybe one more at high speeds. Any differences between quarter and half gauge showing between cars might well be sender/gauge/contact or terminal cleanliness/rad and cooling channel cleanliness etc. etc. etc.


- - -TR7 Spider - - - 1978 Spitfire- - - - 1976 Spitfire - - 1988 Tercel 4X4 - Kali on Integra - 1991 Integra - Yellow TCT

My gauge always sits at about 3/8 and that gives a fearsome heater output if required... Last week we had a 'heatwave' (well - for Ecosseland anyway....nowhere near TX standards - I lived in Houston for a while...) and the gauge moved up to maybe 7/16 but still below the half mark. I say as long as you are not losing any water - don't worry about it.

My gauge usually sits around just past 1/4 when running and then standing still she goes up to 1/2. That is when the fan kicks in and takes it back to 1/4. I have thought about this for a bit and think that as long as it is between 1/4 and 1/2 I am happy.

I have been thinking recently though if taking of the original fan and replacing it with an electric one was a good idea. Oh well it is done now. I could always move the fan to the front of the rad and then put the original fan back in behind the rad, but I am sure that would be overkill

My cars normally run at half mark and the fan cuts in at 5/8ths.

<blockquote id="quote"><font size="1" face="Century Gothic, Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by jeffremj</i>

My cars normally run at half mark and the fan cuts in at 3/4.
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I was always wondering if my fan was coming in too soon, but I start to feel scared when it goes past half way.

Interesting, my car has the fan behind the radiator and also has an electric fan in front of it. The electric one comes on just above half way mark on temp gauge.

SF Roth

Even with the air conditioning going full bore, on 100+ degree days, with a standard engine fan, mine never gets to 3/8 on the gauge.

At that the top of the thermostat is at 89 C, so I think they are safe to 3/4, but I wouldn't want to see above that.

Hasbeen

If I remember correctly, Kenlowe fan installation documentation mentions that you set the fan cut-in temp as that which maintains a low on to off duty cycle - that is, you don't set it at 80C (with an 89C thermostat) as the fan will be on most of the time! If you have the correct fan for the car and follow the instructions you will probably find the fan cut-in temp is at around the 5/8th mark.

I remember with mine I changed the cut in point as I wanted her the run just under half was. However, from what I am reading I may of got the fan to come in a not too early.

With original fan mine always sat at 3/8. Now with electric fan and aluminum rad with 180 temp switch it comes on at 3/4. I have since installed a manual switch as well and try to keep it at 1/2.

Craig '75 2.0 FHC