OPEL CORSA B Sedan 1.6 IE 1999.

I would like to flush the coolant and bleed my brakes.

For the coolant, I have bought German HEPU antifreeze, Anyways, I only have a reservoir bottle and I do not have a radiator cap.I have a garden hose and a funnel and a drain pan.

How do you flush the coolant with only access to the expansion tank? Do you just stick the hose pipe with medium pressure in to the reservoir bottle, after it starts circulating (if it actually does) I can start the car and watch the temperature, then turn on the heater and the fan on 4 for a while, and continue the hose pipe flush. I would reckon a whole 10-15 minutes of this procedure. **

Can i use the German HEPU (96 % percent antifreeze) coolant alone and with no water - so i.e can you in general use antifreeze alone with no water?

We get like -10 maybe worst case and up to +35 degrees Centigrade.

Does my flush procedure sound correct?

Is it okay to use antifreeze alone?

  • Hello anybody home?
    – Imre
    Jan 10, 2016 at 5:53
  • Imre - I'd suggest keeping your question about procedure, but removing the "Can I use X" bit - you could ask it as a separate question (although we may already have that one on the site - will try and find it)
    – Rory Alsop
    Jan 10, 2016 at 10:01

1 Answer 1


I completely forgot about the draining part, but have no time left. So, here about he antifreeze part. May be, I'll write more later

It may work, but is not recommended.

Freezing point

Antifreeze freezes at -15°C. To prevent antifreeze from freezing, add some water, because water is antifreeze for antifreeze.

OK, I had some fun... Seriously, here a typical diagram of the freezing point of an water-antifreeze mixture. It clearly shows that the best effect is achieved at about 60% antifreeze in water:

enter image description here

Corrosion inhibitor

You could think that 25% antifreeze would be fine for your climate conditions. But antifreeze also inhibits corrosion inside your motor. Therefore, you need at least 50%.

Heat capacity

The term heat capacity describes how much the temperature increases when you add some heat energy.

For water, it is 4.2J/(K * g) This means, to heat 1 gram of water by 1 K (same as 1°C), you need 4.2 Joule.
Other liquids are somewhere in the range of 1-2J/(K * g).

This makes water a superior coolant liquid, but with pure antifreeze, your car could overheat in the summer. Again, the less antifreeze, the better.


Antifreeze has a low viscosity (i.e. how easy it flows. Honey has an extremely low viscosity). This will lead to a lower flow and so less effective cooling. I'm not sure how big this effect is, but at least, it will have a small effect on fuel consumption.

Finally, most points say that more water is better, but the corrosion part dictates that you should at least have 50% antifreeze, though you don't need the deep freezing point.

Too much coolant also has some adverse effects, so you shouldn't use pure antifreeze, too.

Stay with 50%, it's also cheaper.

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