thermostat or no thermostat, that is the question

[supergreenmachine73]

I have recently removed my radiator from my mkIV Spitfire due to a rupture in the core, and a weakness near where the cap screws on  
It has gone to a radiator repair specialist for complete restoration - I am told it will be like new when I collect it. I set about stripping out old hoses, then heater control switch, and the thermostat, and I am in process of flushing out the whole system. But talking to the radiator special ops guy he advised to not bother putting the thermostat back in - unless I planned to use the car in cold winter weather  

What is the general consensus on running the system without a thermostat?
Anyone tried it?

I'm a bit of a stickler for originality - hence the restoration of the my original 16" radiator rather than a full width (export) from the internet.

What are peoples thoughts on using what Triumph intended (regarding the cooling system)???

[Richard B]

Fit a thermostat, otherwise the engine will struggle to get up to the correct operating temperature.

This will accelerate engine wear. You can always fit the winter thermostat (something around 78 degrees)

[supergreenmachine73]

yes thanks Richard. I had my doubts about leaving the thermostat out completely. I think the one I have is an 82 deg one. That seems to be the standard for a MkIV 13oo engine.

thanks again

[Velocita Rosso]

Quoted from Richard B

Fit a thermostat, otherwise the engine will struggle to get up to the correct operating temperature.

This will accelerate engine wear. You can always fit the winter thermostat (something around 78 degrees)

What he says....beware of eskimos selling anti freeze
Always listen to this forum or Triumph owners......unless the repair guy is between 75 and 80  !

[bob dunn]

I ran for years with no thermostat (mk4 spit) but this was to fix a overheating problem caused by an engine full of rubbish in the water ,this was balancing one problem with another and not the way to plan anything.

[Steve AKA vitessesteve]

Never run without antifreeze it raises the boiling point of water and so protects against overheating as well as freezing.  

Not sure about the plumbing on your car but on some cars the thermostat is an essential baffle in the flow.  Even when fully open a thermostat gets in the way of the flow of the water.  Without a thermostat your engine may suffer bad circulation.

[piman]

Hello Steve,

an academic point (as anti-freeze is necessary for other sound reasons), water is a superior coolant to anti freeze as it conducts heat at a higher rate, and the boiling point is irrelevant on a sound system as it shouldn't get near to boiling anyway.

Alec

[RedRooster]

You can always fit a sleeve, this restricts the water flow, i use them in both of the cars.

[JohnD]

RR,
I don't understand how the sleeve restricts water flow.    I use an orifice, the same diameter as that in an open thermostat.  It's cut out of sheet alloy.

Alec,
"the boiling point is irrelevant on a sound system as it shouldn't get near to boiling anyway."
A little misleading, if I may say so.    Water boils when its saturated vapour pressure equals atmospheric, and the water in the cooling system will not boil at 100C because the system is pressurised by the radiator cap valve.   A typical valve is set at 13psi, so the water cannot 'boil' until the temperature rises to 119C, higher if there is antifreeze present.   A small but significant increase, that allows the engine water to run normally at more than atmospheric boiling point.   An experienced driver like you would never remove the cap while the engine was hot, as you know that will lead to an explosive decompression of the system as it boils instantly in atmospheric pressure with steam and boiling water in all directions, especially over you!

And heat transfer; this occurs by three different pathways : Conduction, Convection and Radiation, and the greatest of these is Convection.    This is apparent in everyday life, as we feel much colder when the wind blows.    The movement of the engine coolant is a form of convection, as is the air passing through the radiator, which loses little heat by "radiation"!   Any deficiencies in Conduction and Radiation  are compensated for in the engine cooling system design, and by the benefit of the anticorrosion additives in antifreeze, let alone the the reduced risk of freezing solid in cold weather.    Even when Triumph designed the four and six cylinder engines, these were recognised, as was the need for increased flow in the system- more convection - built in when antifreeze would be recommened.  See: http://www.engineeringtoolbox.com/ethylene-glycol-d_146.html

John

[piman]

Hello John,

I made no mention of specific temperatures as that is a variable, simply it's an irrelevant comparison as in normal circumstances there is no boiling anyway, so the fact that anti freeze solution may boil at a higher temperature is not relevant to which is the better coolant.

The majority of the heat is removed by conduction; convection cools us by evaporation of moisture from our body which removes heat (The basic principle of refrigeration). This does not happen with a radiator as there is no evaporation, it is largely conduction.

Alec

[Pete Lewis]

most dont realise the thermostat does modulate the flow it opens and closes or partially opens and closes all the time,
you need to control engine temperature as the engine relies on a steady temperature or you will have the need to continually adjust the mixture , a steady temp and fuel ratio to correspond is essential.

the triumph specs are in general   88c cold climates,, 82c european, 78c hot climates    there's no winter , summer  for european

wiith a stat fitted and the rad cap Off you will see when idling the  flow across the top of the radiator , it will ebb and flow as the stat changes every few seconds .. its that quick

if the rads working and the fans running the top tank will be at Stat temp the bottom outlet will be nearly cool

Pete

[JohnD]

Quoted from piman

Hello John,
The majority of the heat is removed by conduction; convection cools us by evaporation of moisture from our body which removes heat (The basic principle of refrigeration). This does not happen with a radiator as there is no evaporation, it is largely conduction.
Alec

A common misconception.
Convection = "Heat transfer by the movement of a fluid"  A fluid can be a gas such as CO2 in some Nuclear reactors or a liquid, Sodium in other reactors or water in cars. unless it's an air-cooled engine, when it is once again, gas cooled, but in all cases, by convection.   Evaporation is a special case of convection as the sweat or other liquid evaporates into a vapour or gas and moves away, or is moved by wind, from the source of heat.   Convection occurs when the fluid moves.

Consider 'wind chill'.   At South Pole Station, occasionally in summer there are still days.  The air will not be warmer than MINUS 20C, but it's possible to walk about in shirt sleeves or even as below (note that  the flags are still).   Even though the participants are still losing heat from sweat, it remains around their bodies as a heat shield.   The instant a breeze blows, they are shivering, as convection, the moving fluid of air has removed the heat.

Yes, the heat must be conducted through the metal of the engine and of the tubes in the radiator, but without that moving, convecting fluid, water or air, it will overheat.
John

[DougBGT6]

Despite all the clever stuff John tells us he still says " I use an orifice, the same diameter as that in an open thermostat. It's cut out of sheet alloy" or am I misunderstanding that?

I would strongly advise to do it the way Triumph designed it.

[supergreenmachine73]

Lots of opinions flying around 'for and against' using a thermostat. But ideally I guess I want to run the car the way Triumph intended which is with the spec of thermostat it came out of the production line with. My cooling system was clogged anyway after careful inspection, and before the radiator ruptured it soldiered on in that state. 😲 Hail the battle scarred army of Smiths, Jaeger, Lucas, Stanpart, and other notorious warriors of the 'Triumph campaigns'

There should be a cenotaph to British Leyland, lest we forget!!! 😀

[JohnD]

Of course, you could have used a £2 coin?
The silver middle can be knocked out if you wish, leaving a goodsized hole in your £2 washer!
John

[JohnD]

Quoted from DougBGT6

Despite all the clever stuff John tells us he still says " I use an orifice, the same diameter as that in an open thermostat. It's cut out of sheet alloy" or am I misunderstanding that?
I would strongly advise to do it the way Triumph designed it.

The orifice is to provide a small resistance for the centrifugal pump to work against, increasing its efficiency, as otherwise it is prone to cavitation.
See: http://www.engineersedge.com/pumps/cavitation.htm
I'm not 'clever', I've just taken the trouble to study these things.
The thermostat is an economy device, accelerating warm up, I don't care about that. so KISS!

John

[Basil Fawlty]

Good luck warming up on a cold morning without a stat fitted

If its wasn't required, it wouldn't be fitted

Baz

[RobPearce]

Quoted from JohnD

The thermostat is an economy device, accelerating warm up, I don't care about that. so KISS!

No, it's not just for economy. The engine will NOT like you for making it struggle with cold running for any longer than it should. None of the fluids (oil, fuel, air) are working how the engine is designed for when it's cold. Get it warm quickly, for the sake of your engine. The benefit to your wallet is entirely secondary.

[JohnD]

Ah, but I have an electric fan, that is manually controlled.
So it warms up as quick as an engine without a radiator, until I flick the switch.
JOhn

[RobPearce]

NO, an electric fan simply DOES NOT HAVE THAT EFFECT.

An electric water pump would. Not a fan. Unless you're sitting stationary the radiator is doing its job just fine with the fan off, so you still need a thermostat.

[JohnD]

But with no air going through it, it merely acts as a 'radiator', not a 'convector'!

With the car stationary it needs the fan on, or overheating beckons, whereas it isn't needed while moving.

[RobPearce]

Quoted from JohnD

But with no air going through it, it merely acts as a 'radiator', not a 'convector'!

Untrue. Most of the heat loss is still due to convection, although since this is also true of the things we bolt to the walls of our houses and insist on calling "radiators" I suppose you can be forgiven for not realising that. You might ask, though, why we feel it acceptable to leave them just sitting there if you're so convinced that a stationary car radiator is having no effect!

Quoted from JohnD

With the car stationary it needs the fan on, or overheating beckons, whereas it isn't needed while moving.

You said:

Quoted from JohnD

So it warms up as quick as an engine without a radiator

which is clearly not the same as "an angine with a radiator that I'm not explicitly forcing any air through", and was not, in any case, qualified with "as long as I only sit there idling".

[JohnD]

A car radiator is designed to have water going down it and air going through it, driven A/ by its progress along the road, and B/ by the fan.   It is an active system for heat transfer.

A house radiator is designed to have water going through it, with air passing upwards along it's rails, BY CONVECTION.    This is an entirely passive system.

You can forgive yourself for not having noted these differences in design, but I won't.
In the absence of progress or a fan, air can only pass over the inside or outside surfaces of car radiator, a much, much lower surface area than the complex honeycomb that is provided for through-passage of air.
Moreover a car radiator is always shrouded by the bonnet, so that heated air is trapped around it.

A house radiator is (or should be - I've seen them with ornament ledges over) unshrouded to work efficiently.

JOhn

[DougBGT6]

I read John's link regarding cavitation, very interesting. However these are 40 year old triumph engines design going back even further. I must have changed a dozen water pumps in my time, not one died of impellor cavitation, it was always the bearing! I'd be really interested to hear if anybody on here has actually suffered from cavitation. In the mean time for people asking for advice let me repeat, Triumph designed it to have a thermostat so, why not fit a.................thermostat!

[heraldcoupe]

With the thermostat closed, there is a smaller volume of water being heated by the engine.
Opening (or removing) the thermostat increases the volume of water through which the engine's heat is dissipated.

To put it in it's simplest terms, try boiling a kettle full of water, then try it with only a cupful. They don't boil at the same rate...

The thermostat is there to get the engine up to it's optimum temperature as quickly as possible, then to maintain that temperature with minimal fluctuation.

Cheers,
Bill.