P38 coolant advice

A local land rover specialist told me the other day that at this time of year in UK, it's perfectly ok to top up the coolant with water. I just wanted to know if you guys agree, and if so, at what point does "topping up" become replacing completely, or would it be ok purely using water?

Ballcocks

Coolant does other things beside "cool" - It lubricates things like the water pump. It inhibits the growth of bacteria, it reduces corrosion, it acts as a "Water wetter" - ie aids heat flow between the engine and the coolant. In all it is quite a complicated medium. best not to let it go below 50% mix. particularly on an injun prone to overheating.

Thanks, had a good idea that wasn't right but wanted to check. He's normally good and well recommended

The Mad Hat Man said:

Coolant does other things beside "cool" - It lubricates things like the water pump. It inhibits the growth of bacteria, it reduces corrosion, it acts as a "Water wetter" - ie aids heat flow between the engine and the coolant. In all it is quite a complicated medium. best not to let it go below 50% mix. particularly on an injun prone to overheating.

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Sorry mate but it certainly does not lubricate the water pump. Water pump bearings are sealed units. If any water gets into them even with super lubricating coolant in it they are destroyed PDQ.

Problem is come winter you forget to replace with correct mix of anti-freeze and then uh-oh...

I do 50-50 mix all year round and change every year.

The coolant mix also raises the boiling point, as well as lowering the freezing point...like lanmjdun says, if the water in the block freezes it expands and can do lots of damage.

The Mad Hat Man said:

It lubricates things like the water pump.

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as I said .........

It is ok to top up your anti freeze with neat water as long as you're not doing it every couple of days or even monthly. If you are topping up frequently then you must have a leak. You should change your a/freeze (corrosion inhibitor) every two years and run at 50/50 a/freeze/water and just topping up with water between fills would be ok as long as you do not have a leak. If your cooling system is working properly it will very rarely need topping up.

spadgr said:

You should change your a/freeze (corrosion inhibitor) every two years and run at 50/50 a/freeze/water

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that depends if yu are using the standard blue stuff or the "longlife" OAT

The Mad Hat Man said:

as I said .........

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Ok how many things like the water pump does it lubricate? Because it certainly does not lubricate that other than the seal. There is nothing else in a cooling system to lubricate that i am aware of. The addatives certainly inhibit some contaminants in water to prevent deposit build up and corrosion. Glycol has a lower freezing point and higher boiling point than water. But that's about it really.