How important is coolant antifreeze/water ratio ?

[Semnoz]

Due to a recent issue with a leaking coolant hose (very short hose hidden away next to the EGR), I had to top up the coolant fluid a few times; sometimes water (if that's all I had) and sometimes orange antifreeze (when I've stopped at a garage).

And given the lack of history before I got the car, I have no idea what the antifreeze/water ratio is.

Once I've replaced the host, is there any harm in me just topping it up with 100% antifreeze ?

In other words, is there any risk in having, say, 2/3rds antifreeze and 1/3rd water ?

[Tony500]

I always do a 50/50 mix. Apparently it needs water mixed in for heat transfer, don’t seeing it doing any damage though.

Personally I would do 50/50 or close to it. 70% coolant should be fine

[apersson850]

There's not much to gain from going above 50/50. Due to the temperature curve, I wouldn't recommend going above 80/20.
This is in Swedish, but you can see the temperature curve for different mix ratios here.

[SwissXC90]

Originally Posted by Semnoz

Due to a recent issue with a leaking coolant hose (very short hose hidden away next to the EGR), I had to top up the coolant fluid a few times; sometimes water (if that's all I had) and sometimes orange antifreeze (when I've stopped at a garage).

And given the lack of history before I got the car, I have no idea what the antifreeze/water ratio is.

Once I've replaced the host, is there any harm in me just topping it up with 100% antifreeze ?

In other words, is there any risk in having, say, 2/3rds antifreeze and 1/3rd water ?

Extremely important if your vehicle will be in regions of the world where you may be approaching the lower limit of your antifreeze.

Where I am in Switzerland, we have areas that can reach -20°C in Winter.
If your car is parked outside in one of these areas, you need to be really sure your coolant is protected down to at least -20°C. Otherwise your engine is damaged when the coolant freezes and expands, and that is not good at all.

But if you have coolant made for -20°C, and you dilute it a little bit, and your area of the world never gets colder than 0°C, then you are likely to be OK as you have 20° of reserve to play with.

[Laird Scooby]

If you're unsure what antifreeze it previously had and you've used an assortment of different types, i'd strongly recommend doing an aggressive cooling system flush including back flush. The reason being is that if ethylene glycol and OAT (Organic Acid Technology) antifreezes come into contact with each other, they form a gel. This gel can (and will) block smaller bore coolant pipes/hoses resulting in hot spots, overheating and potentially HGF or worse.

Generally speaking a 50/50 mix will protect down to -30C and more importantly, has the corrosion inhibitors to prevent the internals of the engine corroding.

If you check your handbook, it will probably state in there the recommended mix for this country and if it is 50/50 then it will be because it needs the corrosion protection.

[Tatsfield]

+1 Don't add antifreeze unless you are 100% sure of what the existing antifreeze is in your cooling system. They used to say not to mix blue and orange but even that is not 100% reliable for all antifreeze types, so best totally drain and flush and refill with new. The only way not to take this risk is to only add water and that substitutes the risk of under protection in cold weather.

[green van man]

If it's orange it's not Volvo coolant, which is green. As it's not original I would flush and renew, preferably with Volvo as it's largely fit and forget so while possibly more expensive initially long term will save money.

The problem with non original coolant is you have no idea how it will effect seals etc. it may be fine but if it's not it can get expensive.

Paul.

[ksmi]

If in doubt flush it out! Do you have an antifreeze tester? If not, should get one,worth their weight in gold/repair bills!

Regards,Keith.

[Laird Scooby]

Originally Posted by green van man

If it's orange it's not Volvo coolant, which is green. As it's not original I would flush and renew, preferably with Volvo as it's largely fit and forget so while possibly more expensive initially long term will save money.

The problem with non original coolant is you have no idea how it will effect seals etc. it may be fine but if it's not it can get expensive.

Paul.

That's actually pretty worrying! If the original Volvo coolant is green, that is almost certainly ethylene glycol. The orange stuff is usually OAT so if those have been mixed then as i suggested above, a seriously aggressive flush is in order.

[Semnoz]

Thanks for all the answers - that's made my mind up to renew all the coolant.

Apparently it's not a simple job though due to potential air-blocks. Or can it be done DIY ?