Water Temp

[Elanman99]

Under my therapist's direction, my doctor, Dr. L. Otus prescribed a brisk outing.

Our discussion brought up modern cars and how the temperature stays stable under almost all operating conditions. So why does the Elan's system have these wild mood swings?

On modern cars what stays stable is the needle on the temperature gauge (or the digital display).

Do you believe is showing the correct temperature?

The gauge might appear to have a nicely calibrated scale but pound to a penny its gets its reading via a whole lot of electronics and an even bigger lot of software.

The engine cooling system temperature is regulated by a mechanical thermostat (like the one in Elans) and I'm sure the actual coolant temperature varies with running conditions (as the Elans does). Car manufacturers have decided that the majority of drivers are not really interested in the precise coolant temperature so they tweak the display to give the driver peace of mind. If a hose does burst or there is a genuine problem the (non linear) gauge (and probably a warning light) will come into play.

Ian

[prezoom]

Well, the thermostat is rated at 190 degrees, and was checked in a pan of water on the cooktop with a candy thermometer. I have used two different combination gauges and both read identical temps. One, an early type, with a 60 pound oil pressure gauge, and a later style gauge, with a 100 pound oil pressure gauge. I am satisfied with the readings.

The car does have screened holes on each inner fender well. When the engine is unstressed, I believe the aluminum head, benefitted with additional under hood air flow, will actually act as its own heat sink, and the radiator sees little use, hence the low readings on the gauge. I have not closed off these vents to see if it makes a difference.

The cooling system is in excellent condition, with a recently re-cored original radiator. When the thermostat housing is removed, without lowering the water level, coolant will run out. The thermostat does have a 1/8" air bleed hole. The radiator remains full of coolant, which tells me the coolant recovery bottle is functioning as designed.

[JohnP]

Since reading all this I have been thinking too hard about some of the points raised.

Some coolants are advertised to boil at higher temperatures and with lower vapour pressures for a given temperature than water, which for obvious reasons perform better in that there is less tendency to pressurise the water system. However, if everything is working normally there seems little advantage in this.

If there is a coolant or additive that changes the heat transfer characteristics of the fluid to the extent that is makes it better at pulling heat from the engine, then surely it will result in your thermometer recording a higher coolant temperature if it is recording the temperature of the water coming out of the engine. The coolant contacting surfaces in the engine itself be running slightly cooler though.

As the more effective coolant runs through the radiator it will cool down better and enter the engine at a lower temperature relative to a less effective coolant although not necessarily cooler in absolute terms because it went into the radiator hotter.

Unless I'm mistaken then, assuming the coolant contacting surfaces in the engine are hotter than the coolant, the higher the coolant temperature, the more efficient the cooling process since the rate of energy transfer higher with a higher temperature difference between radiator and surrounding air.

in summary though, what claims to be a more efficient coolant should result in the engine water exit temperature being higher rather than lower.

Are the people who sell coolants that appear to result in a lower coolant running temperature actually selling the wrong stuff?

Comments alumni?

JP

[Gray]

I was tempted to comment that thank god no one had mentioned the dreaded subject alternative coolants! But now they have.

My take on the alternative 'waterless' coolant. Glycol based with higher boiling and lower freezing points,but significantly reduced specific heat - about 25% lower than water. Therefore, 25% reduced thermal transfer assuming wetting, etc. is similar. Therefore, higher temperatures in the same circumstances are inevitable unless someone can explain different, I've yet to see an objective explanation.

Gray

[rgh0]

In simplified terms the equation that governs heat transfer from a source such as the metal of an engine to a fluid such as the coolant is as follows.

Q = HTC x Area x Delta T

Q = rate of heat transfer

Area = The contact area between the fluid and the surface and is fixed in the situations we are talking about inside an engine.

HTC = heat transfer coefficient which is specific for the physical situation and materials involved

Delta T = The temperature difference between the surface and the fluid

The HTC for waterless glycol coolants is less than for water. Thus a higher Delta T is required to remove the same heat from the engine. The waterless coolants also have a lower specific heat (Cp) so that they rise faster in temperature as they absorb heat compared to water. This reduces the average Delta T as the coolant flows through the engine meaning the coolant has to heat even more by the time it exits the engine to remove the same amount of heat. Waterless coolants are also higher in viscosity than water and due to this their circulation rate is lower and thus the mass flow of coolant though the engine is lower and this again raises the temperature of the coolant at the engine exit and the engine metal.

Note that HTC improvers like Redline water wetter reverse this situation and lower coolant and metal temperatures.

The rejection of heat from the coolant fluid to air through the radiator is governed by the same equations. Typically the radiator metal to air surface is what governs the rate of heat transfer here as inside the radiator tubes the HTC is much higher from coolant to the metal tubes than from the radiator tubes to the air which is why the area on the air side is made larger through the use of fins on the outside of the radiator tubes. The hotter coolant makes rejection of heat to the air easier and the lower Cp and circulation rates means that the coolant exit temperature from the radiator will probably be lower than with water.

The overall result of the balance of these effects will be a coolant fluid that runs hotter at the engine exit where it is measured and higher engine metal temperatures will result. The 10 or 20 degree higher average engine metal temperatures can dramamtically shorten the life of an aluminium head as the aluminium softening rate accelrates rapidly with temperature. Typical metal temperatures may be 20C above the coolant temperature so a twin cam cylinder head that may have an operating life of 50 years before it softens excessively at 110 C metal temperature may have a life of 25 years at 130C or 1 year at 150C or a few hours at 170C etc so its desirable not to have excessive metal temperatures either through loosing coolant and boiling the engine or through using waterless coolants that raise the metal temperatures.

cheers
Rohan

[lotocone]

Thanks for the refresher class on heat transfer Rohan.? .It was one of my favorite studies?in college?back when we used slide rules for our calculations.?? Anyone else remember those things??

A friend is thinking about using waterless coolant, so I'll let him know about the compromise it could present. I'm glad you brought it up.

Bob

[rgh0]

Thanks for the refresher class on heat transfer Rohan.? .It was one of my favorite studies?in college?back when we used slide rules for our calculations.?? Anyone else remember those things??

A friend is thinking about using waterless coolant, so I'll let him know about the compromise it could present. I'm glad you brought it up.

Bob

Still have half a dozen different slide rules in my desk drawer including one from my Great Grandfather which is a spiral slide rule accurate to 5 figures and equivalent to a straight slide rule 83 feet long around the spiral in length. Also have my original HP35 calculator still on my desk that I got in final year of university in 1973 to replace my slide rule I used every day during Uni before that. That one was used by my father and it is also interesting as it was "Made in occupied Japan" in the late 1940's

cheers
Rohan

[lotocone]

That's a nice collection of slide rules, especially the spiral one from your Great Grandfather. I missed out on the HP35 by a year or so during my student days. My yellow Pickett slide rule is here somewhere. I'll have to dig it out and see what I can do

Bob

[msd1107]

Still have the K&E slide rule my father gave me in high school. It probably dates from when he was in college in the '30s.

Also have a circular slide rule.

And a HP41 and a HP12

I was a member of ANSI X3J14 which standardized the FORTH language - also a RPN virtual machine. Wrote a HP41 emulator in FORTH. RPN all the way!

Lotus fits the mold.

David
1968 36/7988

[alan.barker]

hi Mark Gasman,
on my Elan Sprint 1. i make sure the correct Rad Cap with double seal is in good condition.
2. the small hose from Rad to Overflow Bottle has no leaks and end
submerged in half filled Overflow Bottle.
3. Foam is in place above Rad and sides. Deflecter card below Rad in place.
4. Rad inside and out nice and clean.
5. Fill system with a good quality AntiFreeze.
6. Timing set with Strobe
Never a problem with small Rad
Alan

[Quart Meg Miles]

I was a member of ANSI X3J14 which standardized the FORTH language. David
1968 36/7988

That was a biblical language: "Go FORTH and MULTIPLY".

Still use the Faber-Castell rule I bought c1961 before 'A' levels (where I wasn't allowed to use it) and am on my third HP calculator: HP45 1973 stolen with Elan 1980, 34C broken display after dropping, currently 48G which is over-complicated. Can't handle non-RPN. Spiral slide rules were Otis in the 60s, I think.

Rohan, you once advised that the thermostat should have the bleed hole towards the exit pipe (I believe that was the way round). Why does it make much difference as it is only allowing a small passage of fluid while it is cold otherwise the thermostat will never know when it is hot?

[prezoom]

Most engines that I am familiar with have some sort of bypass that allows water circulation during warm up, prior to the thermostat seeing enough temperature to open. It appears the only way this will happen on the TC, is if the heater water valve is open.

On the Zetec I am installing in the Plus2, the original thermostat is a dual phase unit, in that as the water temperature rises, the thermostat closes off the warm up bypass circuit. This bypass allows water to circulate, thus preventing hot spots in the cylinder head during warm up.

Most of the water rails used with the Zetec to re-direct the water flow, when the engine is installed in a north/south direction, do not incorporate this feature. Thus resembling the water system in the TC. I personally like the idea of water circulation during the warm up process.

As a result, I decided to construct my own version of the water rail, incorporating the bypass feature. Additionally, I was not enthused with having the water rail running parallel with the head, directly over the exhaust. The Zetec conversion is still "under construction" with hopes of having a running car by the end of January. Seeing this will be the dead of winter, with temperatures sinking below a bone chilling 60f, the new water rail should get a fairly good test of its operation. Summer in this reclaimed desert I live in, should test the opposite scale.

During the thought process of designing and constructing the new water rail, gave thought to making a similar adapter that would install directly below the thermostat in the TC. This adapter would be T'eed into the return water line from the heater core to the water pump, and act in the same manner as the more modern Zetec system. Not sure this is necessary, as the TC has been running just fine for over 50 years, but it would provide a more even warm up for the cylinder head.

[holywood3645]

Yes Rob, it does get bitter cold here!

[rgh0]

I was a member of ANSI X3J14 which standardized the FORTH language. David
1968 36/7988

That was a biblical language: "Go FORTH and MULTIPLY".

Still use the Faber-Castell rule I bought c1961 before 'A' levels (where I wasn't allowed to use it) and am on my third HP calculator: HP45 1973 stolen with Elan 1980, 34C broken display after dropping, currently 48G which is over-complicated. Can't handle non-RPN. Spiral slide rules were Otis in the 60s, I think.

Rohan, you once advised that the thermostat should have the bleed hole towards the exit pipe (I believe that was the way round). Why does it make much difference as it is only allowing a small passage of fluid while it is cold otherwise the thermostat will never know when it is hot?

The bleed hole in the thermostat allows a small circulation of water when the thermostat is closed ensuring the thermostat is sensing the current water temperature at all times and is not stuck with a dead zone of cold water below it so it does not open when it should.

Most thermostats these days do not have a hole so worth drilling a 3mm hole in the flat disk section. Thermostats back in the 60's often had a small jiggle pin in the bleed hole with a ball on one end and a T on the other. The pin moved around loosely in the hole and prevented build up of any corrosion that would block the hole. This is probably not needed with modern coolant corrosion inhibitors.

cheers
Rohan
HP 35
HP 41C
HP 32SII
HP 12C
HP 15C emulator on my iPhone
Fuller 1879 spiral slide rule

[john.p.clegg]

"The bleed hole in the thermostat allows a small circulation of water when the thermostat is closed ensuring the thermostat is sensing the current water temperature at all times and is not stuck with a dead zone of cold water below it so it does not open when it should.

Most thermostats these days do not have a hole so worth drilling a 3mm hole in the flat disk section. Thermostats back in the 60's often had a small jiggle pin in the bleed hole with a ball on one end and a T on the other. The pin moved around loosely in the hole and prevented build up of any corrosion that would block the hole. This is probably not needed with modern coolant corrosion inhibitors. "

I always assumed the hole was to allow any trapped air past the thermostat,so it was sensing the water temperature not the "air" temperature...and the "jiggly" thing was for the same purpose as a float,would allow trapped air through but restrict the water ??

John