Hello, I installed a Water Temp Gauge. I was wondering if anyone knew what the normal operating temperature should be on a 70 degree day and driving on the highway.

Hello all!

I went out and found this chart.
https://durathermfluids.com/pdf/techpapers/pressure-boiling-point.pdf


It discusses temperature of plain water @ atmospheric pressure, like an open kettle) and the same under a pressure cap of a sealed vessel.
There is a chart for water with antifreeze too under both conditions.
Going with the idea from another posting that the cooling system will be under 11 psi so that it does not lose Coolant the 8 PSI is very realistic.

After looking into those temperatures you will ask why so much more heat over a thermostat setting that opens in the 195 degrees area.
Well, this is when the thermostat will just "crack open" not fully open. The design of the system is not up to its operational temperature as it should be higher. This is only the first flow temperature or minimum. If you go into a long downhill coast or turn on a heater you want a buffer reserve in the engine.

In the paragraph above the charts it explains what is happening down inside the engine next to the cylinder walls or what we don't want to happen throughout the cooling system.

Of course it took evolution to get this idea proved.
After years of having what works keep on working like in the days of steam engine trains that Constantly was adding water at every fuel stop not so well for cars.

Somewhere with the advent of increasing the number and their size of cylinders pressure caps came a long. Some of you may remember we use to leave the radiator purposefully low in Coolant so not to add water unnecessarily. This always created an air space that put air in the Coolant when circulated.

Somewhere in the "muscle sixties" the hot rodders group figure out that a bigger radiator and water was heavy!
Now some students, with slicked back hair or maybe a curly haired chick that had not fallen asleep quite yet were listening. He or a she, told their friends and began to network, as we call it today, but under hoods in front of multiple carburetors and thought about that wasted air space.
A recovery bottle was added for a catch basin and it was about then, the bubble gum went flat under the desk!
A radiator cap was made to allow the Coolant back in after the radiator Coolant cooled back down.
The air space was gone and and amazingly, a gain of cooling happened to boot! Say what?
Now was it an accident that the air bubbles got figured out to be an insulation or was it some Einstein event. We will never know as NASA might have taken credit for it. It was the Sixties you know?

Anyhow, it comes down to antifreeze becomes a thermal fluid additive that enhances water density up,to,a point. That's why I chose this sites charts. Still Water is best refrigerant know to man, except for Hydrogen. It works better pound for pound moving BTU's over any of DuPont's inventions.

As far as where to mount a gauge the head is probably the best place. It's the highest point in the system and heat rises. Of all the areas that you think get hot this is where the water is less dense and we need to be concerned with heat transfer as those parts in the head are getting flamed!

The thermostat is on the outlet for the closest response. All the water is under the same pressure through but the last of the final heat transfer is all done by the point. From that point on outward we need to lose it. As a "rule of thumb" all of the heat transfer across the radiator is a 30+degree drop by design. The quantity of mass and speed flowing through a cooling medium's size, is a design factor. Water and air have fixed factors.

So, once the thermostat cracks there is a lag time before you reach a design temperature of stabilized operation with the design to be sufficiently large enough to cover in excess of expected temperature with a margin left for some aging and lack of maintenance.
Having the temperature of the Coolant higher than the crack open setting is not uncommon to avoid over cooling. So I agree with other posts of 5 or 10 degrees being normal.

Using mechanical gauges or infrared you have to allow for variances, i.e. Aluminum, rubber or brass conduct differently. In refrigeration, I allow approximately 10 degrees from the pressure reading of refrigerant converted into degrees inside versus the outside of copper tubing of heat exchangers.

If you measure a thermostat outlet you are probably under in temperature of up to 10 degrees of the actual center of the Coolant flow being slightly hotter.

On the car radiator you can measure the inlet to the outlet as a comparison and see an overall drop of at least 30+ degrees. I can usually read it in idling mode to be 150 degrees on the lower hose.
I would not want to see it less than that. If it is, the thermostat is broken in the open position and is not closing. Most likely causing slower warmups and richer running.

You can measure down the radiators face and "you should see" the most drop in the first upper half, if the radiator is flowing and breathing through correctly. It should not be nearly as hot at the bottom as the top.
If not and you feel cold spots or read cold spots in the radiator tubes it has an issue of being clogged, missing fins or something. A radiator in this shape the engineered design is going to fail near it's "top allowance" for that hot summer day. The radiator should alway be able to throw off mor heat than the engine can make.
Turning on the heater valve adds about half a radiator of size with its fan on. If the temp then drops from being to hot, the radiator has a problem.

You have to play with your thermometers and takes notes. Compare what is normal on the inside gauge and expect repeat performance within a minor range or you have a problem starting.
Just like a voltmeter know the where from where and let that be its normal.

Hope this "tunes you in" a little better. (:)
Phil

And for additional fun, most contemporary engines have switched over to having the thermostat on the coolant INLET of the engine, instead of on the outlet. That's how the LS3 in my 242 is set up and also how the 2.3L Duratec in my buddy's MG Midget works. So, the temp range that the t'stat operates at (around 186-189 in the case of my LS3) is always lower than the temp of coolant leaving the heads (around 198F in mine). Set my PWM fan controller to operate at 204F and things are working perfectly. Previously, with an engine that had the t'stat on the outlet, I had a 180F t'stat and the fans set at 187F.

Hi there,

I did thought during my post last night that a thermostat put in the inlet side would work too. The water is heavier or more dense when cooler. This might be splitting hairs but at my age as I have fewer to be abused.

Maybe you can answer a few questions for me about V8's.


On my old 74 Ford 360 the water pump has a bypass hose or at least I think it's a bypass, sticking out the rear of the water pump.
I was wondering if that actually pushed water through the intake manifold and into the banks. This would heat it up sooner for emissions back then. Could it be there to circulate water through the two heads banks until the thermostat opens up that is in the intake manifold.

How does your V8 heat up as the water is going to rise up and over to the radiator by convection, if it can flow?
The water pump have a way to circulate at least some water using a bypass channel or something?
Maybe the pumps for V8's or that block has away around there being any stagnant water movement until the stat opens.
Guess I'm again splitting hairs that the engine heads are really on their way to death quicker if the thermostat fails closed. (:-(

Its been so long since I have had to change out a Volvo pump I have forgotten if there is a small hole in the block behind the pumps impeller area? If so, Maybe it's there to push water through to the heater core and back on the return pipe that goes around the engine.

I dropped wanting V8's like a deadly bad habit. That was until I had a Chevy 454 giving to me in an '87 Motorhome. The motor home reminds me of what a beast a V8 can be.
My pickup truck has been sidelined for the last 11 years. The timing chain went bye bye at 180k. The engine was very tired and not very heart warming over the years anyway.
Both are Super duper heat generators and the gas guzzlers.
I have the engine halfway out but my old V8 enthusiasm has largely waned to where we both should be in museum or scrapyard.

Thanks for the update on contemporary engines, I needed it!

Phil

My understanding is that the bypasses are there so the pump isn't damaged by trying to pump against a closed t'stat. Not all V8's are the same in this regard. The 5.0L Ford bypass literally bypasses the t'stat - runs from behind it back into the suction side of the pump. The LS has a bypass in the form of fluid running through the heater core -- heat is on/off by controlling air across the core. On mine I simply installed a small (1/4") tee across the heater hoses since my car needs to be able to cut off flow to the heater core when the A/C is on (water control valve). The Ford intake manifold only had coolant flow from the front of the heads into the t'stat housing -- the entire intake is NOT 'heated' by coolant. The LS uses a plastic intake -- no coolant in the intake at all. The ins/outs of coolant are from the block to the water pump.

My understanding is that moving the t'stat to the inlet side was primarily done to facilitate making it easier to fill the engine with coolant without getting air trapped.

Hi there,
I will have to stay on the lookout for more articles of engine design changes. Some of the tricks they come up with have merit after they stand the test of time and a few copies are sold to get the bugs out.
High silicone aluminum for engine blocks took on a lot of mistakes in their beginning.
The LS, from what I have read is pretty popular. I have thought about junking the 360 CID if I can fall back in love with the '74 body.

Thanks for the light on the many ways there are to do things.
Phil

The challenges with aluminum blocks (Euro mainly) with higher silicone content and special prep for the cylinder bores is largely solved by sleeving the blocks with iron cylinder liners -- most OEM stuff has come that way for quite some time.

As a comparison - the 376 cube LS3 (alum block/heads) in mine weighs 70 lbs. less with a 9.2" deck height than a cast-iron head/block 302 cube Ford with an 8.2" deck height. It weighs about 140 lbs. less than a cast iron head/block 351 Ford with a 9.5" deck height. By moving the battery to the trunk and putting lighter weight bumpers on my Volvo, the total weight and front/rear distribution is pretty close to what it was with the original 4 cylinder. A bigger difference occurs when a passenger is in the car than with the engine swap. So I'm a big fan of the all aluminum V8 I chose.

Would you please describe in detail what you installed and how?
--
Art Benstein near Baltimore

A husband got in big trouble after his wedding anniversary.
His wife told him the day before: "Tomorrow there better be something in the driveway for me that goes zero to 200 in 2 seconds flat."
The next morning the wife found a small package in the driveway.
She opened it and found a brand new bathroom scale.

Hello Art,

Sorry for the delay. I have installed a 52mm VDO Water Temp Gauge with the correct sender via an adapter that fits in the radiator hose (made by Auto Meter). Out of curiosity I installed an extra sensor on the lower hose as well (because I am replacing hoses anyway). I was shocked at how long it took the thermostat to open and after it did the readings on the lower hose never reached 140 degrees. Granted it is 70 degrees outside here in the Houston area. I just wondered what the readings should be on the upper hose.

5-10 f higher than the thermostat rating at idle...about 0-5 f higher steady state cruising on level ground at sane speeds.

Pro tip...if it is always reading about 210 f it is because your system is not pressurizing or the block is partially empty (or both).

I can't say the specific temp -- guess that would depend on the thermostat used. Under most ordinary circumstances the needle on the original gauge will read dead center. -- Dave

Yes, but that's mainly because the instrument clusters keeps it there in a pretty wide band of temps. Not until the temperature creeps up to unsafe levels will it start to rise towards the red.

This was done on purpose as the coolant temperature may vary quite a bit during driving. That's perfectly normal, but it worried drivers unnecessarily.

I used to have an Amazon with the ether (or some other substance) filled hollow tube sticking in the head and transferring the temp to a bi metal temp gauge in the instrument cluster. So no compensation whatsoever, this instrument always showed varying temps. Much more so than you would expect.

I once took it on holiday to Austria on a pretty hot day (for our climate, that is) around 33 C (~91-92 F), the needle was nudging up against the red all the time while driving around 100 km/h (~62 mph). The cooling system was in perfect working order.

The same trip under the same circumstances with my 1992 245 doesn't see the needle anywhere as near the red as on the Amazon, but I don't think that its cooling system has much different capacity...

Long story short: if your auxiliary meter doesn't apply the same "steadying" of the needle as the original does, expect to see varying temps, some of which may start to worry you.

The correct thermostat starts to open at 89 C (~ 192 F) and is fully open at 100 C (212 F). At steady speeds under the conditions you mention, I would definitely not expect to see a temp above boiling point because I don't think that the cooling system will pressurize much above ambient pressure (maybe a bit but not very much).

There was an ancient post on this BB by a guy who installed a temperature sensor in the upper rad hose plus he tapped into the rad overflow hose (the little one that goes to the top of the reservoir) with tubing that lead to a dash mounted pressure gauge.

He said that after cold startup the first thing to show activity was the pressure gauge, which started to increase well before either temp gauge reacted. Then the Volvo dash gauge and finally the hose-monitoring gauge. (This makes sense, as the Volvo gauge monitors the coolant temp in the cyl head, and the hose doesn't get hot until the thermostat opens.)

Old-timers on this BB may remember that post and the poster's description of the action of the various needles which he described as "a bit of Kabuki theater".

I tapped into that same upper line with a little 0-30psi gauge and found the same as he did...pressure rises before any temperature indication on whatever gauges you have. It's due to thermal expansion of the coolant in a confined space. This assumes the pressure cap is sealing correctly. My system pressured up to a steady 8psi at full operating temp. with the stock 75kPa (11psi) cap.

Aftermarket gauges I have used don't even register until temp. gets to 130F or so. That's typically the minimum on their scale. I think the Volvo dash gauge is like that. At least my non-compensated 1983 is.

I have tested some aftermarket gauges both mechanical and electrical, and the only ones that had decent accuracy were the more expensive ones such as VDO, Autometer, and such. Those little 3-gauge panels from the FLAPS are particularly bad.
--
Bob: Son's XC70, my 83 244DL, 89 745 (Chev LT-1 V8), 98 S90 (recently sold) and 2010 XC60. Also '77 MGB and four old motorcycles