High temp at water rail

XJ-S
22

Gary, you’ve got me beat with time owning an XJS V12 … by 1 year … I’ve had mine 15 years, starting my 16th year in February.

Regarding IR cameras, I bought one in 2003 and used it in my construction consulting and litigation consulting business. One of the first, if not the first, to have an IR camera for that use in Florida.

Never did use it on the V12, so you got me there too.

Does that IR camera experience possibility cause me to go in more detail than may be necessary? Without a doubt, yes, I would agree to that.

Does that make it matter if an IR thermometer (had those too) is used properly to get reliable and accurate readings?

Only if one wants to actually rely on the readings.

Otherwise, no, does not matter at all.

I was simply alerting the IR thermometer users to the correct ways to use their IR thermometer guns and what to expect from the distance and angle to the surface being read.

24

Oh no, not again ,… nope … trying your side of things.

Recognizing the limitations of using an IR thermometer, but also acknowledging that there are things which they can be used for in investigating things, I purchased a reasonably lower priced (<$40) IR thermometer from O’Reilly’s which has a 12:1 cone.

The 12:1 cone means that if I point the laser at a surface 4" away, the reading circle is approximately 3/8" if reading perpendicular to the surface (or close to perpendicular to it). If trying to read the temperature of a surface, which has a flat area of less than least 1", from 12" away, and not close to perpendicular … well, the reading is not going to be very accurate as the reading is including other areas and their temperatures.

That said, though, I did some experimenting with the IR thermometer for what it is good for: comparisons of similar items, shapes, and surfaces.

Starting from overnight setting, I shot the IR at both thermostat housing, with the laser about 4" from the thermostat housing, with the laser pointer about 3/8" from the mounting flanges, for a measurement area of 3/8" diameter circle, reading 65.7F each side … engine cold.

After starting the engine, I made additional IR readings on the A side and then the B side, and looked at the temperature gauge needle.

It only took a few minutes for the B side to read higher than the A side, and after about 10 minutes or so, the difference when to 25-30F higher on the B side than on the A side. and basically followed 30F higher all they up until the A side was around 179F and the B side was 201F.

Eventually, the A side stabilized at around 189F+/-3 and the B side stabilized at around 203F+/-4.

I also noticed that the temperature gauge barely rose above C until the temperatures were well over 160F, and even at the stabilized temperatures, the gauge was well below the N.

The car was in the garage (exhausts facing out the garage door) the entire time as this eliminated other factors, such as air flowing in while driving.

The temperature gauge sensor is on the A side, so it is reading the lower temperature between the two banks.

There must be something inherent in the cooling system, even before the thermostats open, which allows the B bank to heat up faster and hotter, and remain slightly hotter even after the thermostats open.

I found that I still have two brand new, in the boxes, Calorstat thermostats, complete with gaskets and seals, thermostat model TH1514.81J. I looked those up and the temperature rating is only 81C (177,7F, likely considered as being 180F).

I don’t know what temperature rating thermostats are in there now as my mechanic swapped thermostats a few times to get ones which kept it right around N on the temperature gauge in the hot Florida summers. Having driven it a few times here the past several weeks and it never even gets close to N on the gauge, yet the IR thermometer, reading the metal and not the water, shows the temperature is around 195F+/-5 (average A&B sides).

How far off is the IR at those thermostat housing points? I would think within 5 degrees or so of the water temperature inside.

I would think that should put the gauge right around the N?

My gauge does not read in degrees, just C … N … H.

25

Jerry I would, say the IR is a good device to provide cursory checks to confirm what your car temp gauge is telling you.
The nice thing about it is its not a fixed location which you can add later. I have not added any additional gauges as Greg has to his car(I may at a later date) but I primarily use it to to confirm if the radiator is doing its job and the t’stat operation. It’s served me well, no issues so far.

26

There are a few points worth mentioning concerning the cooling system on a V12 HE engine.
The design of the radiator, and consequent water flow means that there is more back-pressure on “B” bank and less water movement", so “B” bank will run hotter.
The ports behind the water pump direct more coolant to “A” bank. Same result.
“A” bank will always be cooled more efficiently than “B” bank, unless you place a restriction of some kind in “A” banks radiator hose, to even things up. (Works, on my engine.)

If the Calorstats you mention have “seals” contained with the gaskets, chances are they won’t fit your engine, which does not require seals.

27

I just realized another reason why B bank may always be hotter than A hank.

A bank is always cooled by the airflow of the engine driven radiator cooling fan more directly than B bank is, and the electric fan on the B bank is not running.

That also effects the cooling of the radiator on the A bank side.

I’ll need to rerun the testing with the electric fan running all the time to get a better comparison.

28

Hot air flow around the block exterior I very much doubt cools the insides of the engine.

29

FWIW, perhaps nothing, my V12 has different temps, bank-to-bank. Haven’t checked this in some time but 10ºF difference is ringing a bell. Been driving it that way for years. Something said long ago, and now long forgotten, convinced me that it wasn’t a matter of concern.

I don’t recall if my previous V12 (about 16-18 years ago now) was the same.

Cheers
DD

30

If both my temp gauges are correct

my A bank is 5F cooler than B bank while getting up to operating temperature
my A and B bank are about the same during idling/fan cooling
my A bank is 2F cooler than B bank while driving/cruising

31

Aye, but we are measuring the temperature of the outside of the engine, and air flow over the outside of the engine will cool the outside some. How much? I don’t know.

Now if these engines had cooling fins as air cooled engines have … hmmm … cooling fins add surface area for greater heat transfer to the cooling air.

32

Each has two seals to choose from and a gasket if that is needed instead.

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33

They look exactly like the ones I use in my car (model number wise) . I don’t remember anything about the seals just the t’stat housing gasket.
Also if I remember correctly ensure the jiggle pin is in the upward position.

34

Interesting. The thermostat housings on my engine- one has three bolts , and the other housing, which is square, takes four .I hope they work.
Quite a few years ago I ordered a pair of thermostats from a national chain. One thermostat came with a gasket, and the other with a rubber ring type seal. The second thermostat would not fit the housing and clearly was meant for another application. It was returned to be exchanged, so, just sayin…

35

Okay, new test, new results.

I ran a jumper tesr wire from battery to electric fan, tested fan, worked, disconnected test lead at battery.

Car has not been moved, or run, since yesterday’s test.

Started engine, reconnected test jumper to elevtric fan, within less than a minute, the B bank was 5 degrees hotter than A bank, and over next several minutes the B bank went 10 hotter, 15 hotter, 20 hotter, than A bank.

Then stayed at 20 degrees hotter until 170 on A bank. Expected 190 on B bank, but was only 185.

From that point on, the A bank gained on the B bank until there was 10 degrees difference, with B bank 10 degrees hotter.

Let run an continued checking, but that was less consistent as each side would get hotter by 10-15 degrees, then cooler again. The A bank range was 185 to 200, with the B bank range 200 to 215.

The above was with electric fan running continuously.

The electric fan appears to have made a 10 degree difference in temperature until the thermostats began opening.

Granted, yesterday’s tesr was a ‘one off sample’, as was today’s test being a ‘one off sample’.

Thus, as pointed out above, there are cooling system differences, but the electric fan does provide some cooling (taking exterior temperature measurements). Was this due to cooling effects of air through the radiator or external metal cooling? Because there was little flow through the radiator until the thermostats began to open, I’m guessing not much from the radiator as the flow was only from through the thermostats bypasses.

36

I looked at my thermostat housings closer and, one has 3 bolts, the other 4 bolts.

However, I have two other gasket sets, one old and used, one new. Apparently my mechanic gave them to me with the thermostats in case I replaced them at some point in the future.

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37

That looks more like it. I’m just trying to save you (or your mechanic) some grief in the future.

38

Doing things myself now.

We moved from Ormond Beach (next to Daytona Beach) a year and a half ago to Asheville. My mechanic is in Daytona Beach, so I’m getting back into doing my own stuff again.

Years ago … er … decades ago, I did my own work, including rebuilding two XK engines (from my 1954 XK 140, many years later one from my 1972 XJ6), others engines and a couple of automatic transmissions, among other things.

I’m just a lot slower now. :slight_smile:

2 Likes
39

Just did my thermostats over the weekend. A bank is square with four bolts, B bank is triangle with three bolts. I prefer the black gaskets, they are the new and improved gortex/metal which Ford brought in, not the old paper. Eurospare is what i bought. Identical to Genuine Jag, but cheaper. The thermostats need no seal, they fit right in the housing with gasket behind them.

40

Do you smear coolant or vaseline on your gaskets.
When I change my t’stats the housings were like they were welded on there. Had to use my convincer to pry them off. I was nervous of smacking them too hard.
Which led me to believe that my trusty mechanic had told me he had changed them a few years earlier but they seemed like they had been there a lot longer. And of course they had no jiggle pins.

41

Nope, nothing. These new and improved black gaskets are just like the new cam cover ones and new oil pan ones. They seem to work great between aluminum.

And unlike paper gaskets, these new ones come off easily.

Make sure to use antiseize on bolts.

42

The thermostats began moving (as best I could tell visually) at about 1801F on my small dial thermometer with its sensor in the water between the two thermostats.

At 212F boiling, and letting it boil for a couple of minutes, they each had extended to 1-5/8", measured from the engine side of the flange.

I just need to get some of the better gaskets now. One 3-hole (B bank side) and one 4-hole (A bank side).