31 replies to this topic

[Carlos W]

Ignition timing has been mentioned above, but it's also worth making sure it's not running lean.

 

If the engine is set up properly then an electric fan to compliment the mechanical one is an option

[Ethel]

 Over and over I see over-cooling mentioned, "never run your engine too cool" and I keep thinking how is that possible?

Put that way, the answer is simple - use the correctly rated thermostat.

 

Calculating the potential heat loss from a radiator isn't too difficult. You just need the weight of the water in it and its temperature as it enters and leaves. Add 'em together and half the total to get the average temperature, you can divide the specific heat capacity of water (4200joules/celsius/kilogram)by that average and the weight to be left with the energy (joules).

 

Of course the water is replaced as it circulates, giving you a rate of flow that you can measure in kilograms/time. Though a Watt (power) is a joule per second, so you can have time on both sides of your equation, and total power in has to equal total power out. 

 

Conclusions:

 

The most efficient cooling system has minimal water temperature drop across the radiator.

 

If there is a sizable drop then there's power to be saved by  reducing the flow with a smaller or slower pump.

 

The less water circulating the better the warm up times and economy.

 

 

 

...That is if it doesn't overheat of course!

[yamoke]

Related, i have no wire for the thermostat and my temp is 82° with a fan always on.I guess thermostat is mechanical and a poor repare was made. Is it simple to rewire ?

[Alpenflitzer]

The following thermostats are recommended and <many people change it correspondingly thru the year:

In degree Celsius:

74° Sommer-summer
82° Übergang (Frühjahr/Herbst) -spring/autumn
88° Winter -winter

 

Above all the rad cap must provide the correct pressure for your car and the water pump must be ok.

[Magneto]

Now see, that also is confusing to me - if the thermostat is simply a valve, then closed is closed and open is open, the only difference between the ones mentioned above is the rate of change I would assume. Summer ones open fully earlier and so on.....the diameter of the opening is the same, isn't it?

 

And blocking off the bypass hose - the one between the head and water pump?.....doesn't the car need this? I know they eliminated it on later cars but then the cooling system was routed differently too - front radiator and such. Isn't it's function to send the water back thru the head to cool or warm it evenly till the thermostat opens? Could I just put a restriction in it and improve it's efficiency in winter?

 

I have an electronic supplementary temp gauge I run on my 2009 MINI and it shows accurate temps - and while they do change a bit, the amount is very small.....so I don't understand the comment about modern gauges being different than what's in the classic, the one in the classic is not a capillary tube type, but electric/resistance as well.

 

Most of the comments here pertain to running hot, the OP was concerned about running too cool, which can be just as damaging, and I'm having a similar issue. I wrote it off to the fact that it get's really cold here - today it will be a high of -15C! - but again, my modern cars still come up to temp OK in this weather.

Edited by Magneto, 05 January 2017 - 05:25 PM.

[carbon]

Magneto, sounds pretty chilly in Kansas City!

 

Yes, it is possible to have engine over-cool in cold weather (ie not getting up to proper running temperature). In days of old BMC used to sell 'radiator muffs' for purpose of limiting amount of cold air getting into the engine bay.

 

I remember cutting out a piece of 3-ply hardwood and putting this behind the grille of my '76 Clubman Estate many moons back. This had the desired effect of keeping the engine bay warmer. Before this I had problem with the carb icing up, with the grille blanked off this never happened again.

[Ethel]

The bypass was intended to encourage the water to circulate round the thermostat (it is hanging off the side of the head casting), Metros & later Mini have the sandwich plate heater take off to do the same job. The 'stat isn't a perfect on/off "switch" but even if it were you'd get an effect like a PWM speed controller on an electric motor - if it was continuously switching so it spent half its time on and half off you'd get half flow.

 

Modern electronic sensors are more sensitive/responsive because they don't flow all current to drive the gauge needle with a heated metal strip.

 

Remember a Mini's, comparatively powerful, mechanical fan is running all the time. Even when the air is freezing and the car isn't pushing air through its grille.

 

The cooling system is really about controlling the combustion chamber temperature*, even an alloy engine would withstand far more heat than the 120ish⁰C that will blow your rad cap. The breal difference to  a modern engine is that it can alter the fueling and ignition timing to compensate for temperature changes much better than a good ol' carb 'n dizzy.

 

* different rated 'stats are to compensate for likely changes in seasonal air temperature.

[Magneto]

I understand that the thermostat is not an on-off switch, rather a slow opening temp controlled valve......I may wind up doing the cardboard in the grill thing and see if it helps.

 

Good point on the computer controlled timing and fueling on modern engines helping to control the temps....not only that but on the newer MINI engines there is a two stage thermostat, the second stage drops the running temp from the normal 225* to 185* under heavy load and temp conditions (ambient temp over a certain number, above certain speeds on the highway and/or when the A/C is on "max" )

[Mini Manannán]

You can get the proper grill muff: http://www.ebay.co.u...n-/370763793697  Bit pricey though!  A bit of hardboard would be a dirt cheap experiment though.

  My dad used to cover the grill in the deep cold of the winters we used to have, when I say deep cold  it was nothing like you have there.  It was an annual thing, about December the grill would be 'mostly covered, in February it came off again.  It's nothing like as cold these days though, I run an 88° 'stat all year with a 4 blade fan in Summer and a 2 blade fan in winter.

[tiger99]

Actually, modern cars from reputable manufacturers "should" to have temperature gauges that work properly. (Some are dumbed down because the manufacturer knows that most if their customers don't even know how to open the bonnet.) The only reason that the gauge hardly moves should be that there is a fairly powerful computer regulating the fan and maybe even the water pump, amongst many other things, not simple and crude on/off control like a Mini. The gauge is also more heavily damped than is possible with a conventional mechanical or simple electric gauge, by digital filtering within the computer, to prevent it waving about needlessly. But over a time scale of 30 seconds or a minute you should find that it is quite accurate.

The temperature really is tightly controlled. But you can see warmup and cool down, a peak after stopping the engine, and almost always, if you want to waste fuel and damage the environment, you can find a way of making the gauge go fairly high. It is only like having a thermostat that is precise within its operating range.

But you "could" be presented with an aggregate of all engine temperature sensors including exhaust gas, oil, low pressure fuel, high pressure fuel, ambient air, turbine outlet pre and post intercooler, and coolant temperatures at several places. The computer needs all those for its own purposes. You can probably get them all on the CAN bus at your OBD socket via a cheap OBD interface and laptop. You can even buy things to mount on your dashboard and display them all.

But if you go delving into all if that, you will be wanting the same on your Mini. Scratch an itch and it only gets worse... I know from experience.

I have just finished playing with engine management computers for the week. Resume Monday.

Have fun!

[roblightbody]

As the original poster I feel that there's still confusion about how the classic mini works.

For example, why does a radiator cover help in cold weather? Surely if the engine is cold, the thermostat is closed, so the radiator, and it's powerful mechanical fan, is irrelevant.

[stoneface]

There is always some flow in the water system even when the thermostat is closed.

 

If the flow of the water and heat dissipation from the volume of water in the system is greater than the heat being put in by the engine, it stays too cold and never gets hot enough.

 

The mechanical water pump on a mini is always pumping. Remove the mechanical pump and fit a controlled electric pump and the closed stat will, I assume, allow the engine to get hotter. The problem then is that without some water flow there will be hot spots in the engine.

 

I believe the natural heating effect in the system will cause some flow of water but others probably know better.

 

Putting a cover on the radiator reduced the cooling effect it has and the heat loss from the radiator.

 

That's how I see it and happy to be corrected.

[Ethel]

As the original poster I feel that there's still confusion about how the classic mini works.

For example, why does a radiator cover help in cold weather? Surely if the engine is cold, the thermostat is closed, so the radiator, and it's powerful mechanical fan, is irrelevant.

Isn't only something like 25% of the heat escapes through the cooling system? By blocking off the grille you'll also be increasing the temperature of the air that gets sucked through the induction system. Also bear in mind when the thermostat opens it lets the cold water in the rad into the engine as much as it lets the hot out.

[psychobob]

it's the taking a long time to warm up that i worry about. When the old radiator rusted through on my hornet, I bought a nice shiny alloy one to replace it. Combined with the four blade tropical fan, it takes ages to get up to temperature in winter. On my seven mile journey to work, it just start giving out heat from the heater as i pull into the carpark!  On the plus side, it never overheats in summer. Overkill possibly?

[Alpenflitzer]

We have presently - 15/-16 C ( 5 Degree F) and I do not have any problems with my 88 C-Thermostat. There is no covering the grill. And the SPI s heater runs very well with the vent.

I only open the heater if the water temp is near the middle.

Edited by Alpenflitzer, 06 January 2017 - 04:37 PM.