Another Question About Coolant Bleeding

[mikexgough]

Basics of coolant....... lets look at this bit first which could be like teaching you all to suck eggs.... apologies if that is the case...... and as you can see.... 50% is really the benchmark figure although many Old School mechanics are known to favour 40%.....but that maybe harks back to the 60's and the Hillman Imp...

Why More Antifreeze Isn't Better


Water, with the proper anticorrosion additives, would make an adequate cooling medium for automotive engines. But it freezes, and boils over. Ethylene glycol, an alcohol, is added to extend the boiling and freezing points of the coolant. Why not run pure glycol, and get better freezing/boil-over protection? As you can see from the chart, pure ethylene glycol will freeze at essentially the same temperature as water. At concentrations higher then 70 percent or so, freeze protection is not very good. Also, ethylene glycol doesn't carry as much heat from the engine to the radiator as an equivalent amount of water, which can result in overheating. Stick with concentrations of 50 percent to 60 percent water/antifreeze.



Basic chemistry tells us that pure water is the best coolant, period. The specific heat of water is 1.0. This is the common chemistry benchmark that says that it takes 1 BTU to raise 1 pound of water 1° F and is assigned the 1.0 specific heat number. A 50/50 mix of ethylene glycol (the green stuff) has a tested specific heat number of 0.5 and of propylene glycol of 0.3.
What this means is that it take twice the amount, in the case of the Green/Blue stuff (and over three times for the Red stuff) of BTUs to raise the same amount of water 1 degree!! This means that pure water will remove double the amount of heat and carry that heat away from the source per unit volume. Now, do the arithmetic and you will find out that the more pure water...the more heat gets taken away! Do not confuse this with the boiling point of the coolant. Pure water will boil at a lower temperature than that of a mix of water and antifreeze, as well as freeze at a higher point.

[haydn callow]

I don't think the radiator does very much at all unless you are either
a....moving forward (creating airflow)
b....the fans are on.(creating airflow)

You'd be surprised at just how effective the rad actually is Haydn... Even when stationary! As Mikexgough rightly highlights above, the rad (even when stationary), is a tremendous heat sink... If it's channels are clear and unobstructed, then it works really well, doing it's job effectively, that job being cooling the hot coolant, and storing it till the stat comes into play. Cold always "beats" heat...Once cooling starts, it escalates,the coolant cools the channels in the rad, the rad then further cools the coolant, then so on, and so forth...

As I understand it a radiator is designed to be effective when it has air passing through it....Unless it has airflow it does very little.

And I must repeat..I do not normally have any drop in coolant level after bleeding other than the "normal" expansion/contraction of the coolant which I allow for before finally putting the tank cap on....Works for me doing it my way....others may have different methods and as long as the result is good...Who cares.??

[mikeonb4c]

As I understand it a radiator is designed to be effective when it has air passing through it....Unless it has airflow it does very little.

That's correct. And it can get air moving through it either by the car moving forward, or the fan blowing it through, or by natural convection. The power of this last one should not be overlooked. It will depend on things such as:

* The amount of hot material in contact with the ambient air
* The temp. gradient between the hot material and the ambient air
* the humidity, conductivity etc. of the ambient air
* The way in which strong convection may be encouraged through the radiator.

A really good example of convection in action is the business of lighting an open fire and getting it to draw. When the coals have not ignited and heated, the draw of the fire is 'lazy', and smoke may back into the room unless the flue and fireplace have been well designed. People often hold a newspaper in front of the main opening to encourage air to be drawn by convection through the adjustable opening so that the air is forced through the coals (in this case to increase oxygen supply). Once the coals have caught, the hot gases created by them rise ever more quickly, drawing air faster, which makes the coals burn notter etc. (at some point you close the adjustable grille to reduce air through the coals and throttle back the heat generation. Efficient chimney design will allow the hot air rising up through the chimney, and any venturi type effect that can be gained from a well degined chimney pot, to exert maximum drawing effect through the fireplace entrance. Occupants of the room can often feel a draft on their backs as cold air rushes under a closed door to replace that being caused by air being pulled up the chimney.

The most fearsome examples of this kind of convection were perhaps the firestorms of Tokyo, Dresden, Hamburg, Coventry etc.

I'd have expected the majority of heat generated by an engine to be due to combustion of fuel. In this case heat generation rises rapidly as the engine is made to work. At tickover, provided the ambient air is cool enough and the water pump and rad. working efficiently, I'd have thought it quite possible that the convection that gets going through the rad. is sufficient to keep the engine within limits for quite a long time without intervention by the fans. But that's just a guess.

Frankly, TGP is probably yer best man for chapter and verse on this one I reckon.

On the 'who cares' issue, I'd prefer to have a bit of spare 50/50 mix in the car only to find that the header tank level hadn't dropped, than not to have any with me only to find that it had. On the one occasion when I have done mine, I worked on the basis that it was possible that a little 'settlement' might take place post bleeding (not least because the level drops anyway as the engine cools and since I'm not sure I finished off the bleeding process by topping the header tank sufficiently etc....). In the event, looking back, I don't think I had to top up at all except possibly for the level drop due to cooling.

[haydn callow]

As I understand it a radiator is designed to be effective when it has air passing through it....Unless it has airflow it does very little.

That's correct. And it can get air moving through it either by the car moving forward, or the fan blowing it through, or by natural convection. The power of this last one should not be overlooked. It will depend on things such as:

* The amount of hot material in contact with the ambient air
* The temp. gradient between the hot material and the ambient air
* the humidity, conductivity etc. of the ambient air
* The way in which strong convection may be encouraged through the radiator.

A really good example of convection in action is the business of lighting an open fire and getting it to draw. When the coals have not ignited and heated, the draw of the fire is 'lazy', and smoke may back into the room unless the flue and fireplace have been well designed. People often hold a newspaper in front of the main opening to encourage air to be drawn by convection through the adjustable opening so that the air is forced through the coals (in this case to increase oxygen supply). Once the coals have caught, the hot gases created by them rise ever more quickly, drawing air faster, which makes the coals burn notter etc. (at some point you close the adjustable grille to reduce air through the coals and throttle back the heat generation. Efficient chimney design will allow the hot air rising up through the chimney, and any venturi type effect that can be gained from a well degined chimney pot, to exert maximum drawing effect through the fireplace entrance. Occupants of the room can often feel a draft on their backs as cold air rushes under a closed door to replace that being caused by air being pulled up the chimney.

The most fearsome examples of this kind of convection were perhaps the firestorms of Tokyo, Dresden, Hamburg, Coventry etc.

I'd have expected the majority of heat generated by an engine to be due to combustion of fuel. In this case heat generation rises rapidly as the engine is made to work. At tickover, provided the ambient air is cool enough and the water pump and rad. working efficiently, I'd have thought it quite possible that the convection that gets going through the rad. is sufficient to keep the engine within limits for quite a long time without intervention by the fans. But that's just a guess.

Frankly, TGP is probably yer best man for chapter and verse on this one I reckon.

On the 'who cares' issue, I'd prefer to have a bit of spare 50/50 mix in the car only to find that the header tank level hadn't dropped, than not to have any with me only to find that it had. On the one occasion when I have done mine, I worked on the basis that it was possible that a little 'settlement' might take place post bleeding (not least because the level drops anyway as the engine cools and since I'm not sure I finished off the bleeding process by topping the header tank sufficiently etc....). In the event, looking back, I don't think I had to top up at all except possibly for the level drop due to cooling.

That's what I have observed.

[mikeonb4c]

In the event, looking back, I don't think I had to top up at all except possibly for the level drop due to cooling[/b].

That's what I have observed.

I'd noticed

But this is about having insurance just in case. I took the same line about fitting an LCA. Not needed it yet, but the day will come....

[missfixit70]

Regarding your above (inserted) post Kirsty... (forgive me if i'm wrong /misread it, it's been o LONG day and i'm in wind down mode) How pertinant to the comparison's would you say the difference was from using regular blue coolant, to the carplan red? Is that a variable enough factor to bring into question the actual amount of importance over using a spurious stat over a mazda original?

Doesn't the different coolants affect the variables? And do you happen to know what ratio the opposing coolants were mixed to?

I'm no expert on different types of coolant & their relative cooling properties so I can't really comment too much, just passing on the info & results found. My thoughts would be that it wouldn't have a huge effect, certainly not to explain the difference with Bongo B, apparantly it was always a pig to bleed, but with the Mazda stat & the housing face cleaned up, it apparantly bled much easier & more decisively & then ran with a much lower control range than it had been.

Coolant mix/type - The Blue Coolant used, Comma concentrated Super Cold Master Anti Freeze 2 year protection mixed at 50/50. The Comma Super Long Life Red 5 year protection, mixed at 50/50.

[missfixit70]

I fixed the sensor from one of those LIDL's temp sensors on the outlet at the bottom of the rad, tucked it under the end of the hose then wrapped a couple of alternating layers of foil tape & gaffer tape around it then a layer of the silver bubble wrap type insulation then more gaffer tape to try & eliminate any external air cooling.
Took the bongo for a 10 minute run to warm it up, just as I was getting back home the temp on the exhaust side of the head rose to 76 degrees & the mason modified temp gauge was just to the left of vertical, the reading on the bottom of the rad had sat at 10.6 degrees as the engine warmed up, this started to rise very slowly to about 12.5 degrees as I drove the last few hundred metres more slowly through the housing estate as I approached home. Then once I parked & left it idling on the drive while I was doing a couple of other bits, must have been 5 or 10 minutes, the temp started to rise more quickly at the rad outlet , while the head temp only rose to around 80 degrees - just before vertical on temp gauge, until the gauge went off scale, so I measured with a laser thermometer, with the rad inlet at 91 degrees, the rad outlet was 78 degrees. This continued to rise as it sat idling until the rad inlet was 98 degrees and outlet was 86 degrees & I think it would have continued to rise if I hadn't switched it off.
So this shows there was only about 15 degrees of convection cooling when stationary & that the bottom hose SHOULD GET HOT.
If it's only getting warm, you either haven't been at it long enough, the stat isn't working right (not lifting high enough or not shutting off the recirc inlet properly), or you have another problem IMO.