Very basic engine coolant question

[Mercutio]

Relative newbie so go easy on me

Our Toyota Yaris (1.3, 2010) is low on engine coolant. So far, so normal.

I’ve purchased some Halfords general stuff by putting in my reg and the system “matching me” with the correct coolant

However all forum posts say “never mix engine coolant, always use the same one as manufacturer etc”

So question is this:

Can I safely “mix” and add this coolant?

Or do I need to take it to a garage and have the coolant “drained”, then fill it up with the new coolant as the only one?

Any advice very gratefully received!

[E-bmw]

You don't need to take it to a garage, you can do it yourself but, yes someone needs to drain & refill your system or alternatively you need to top it up with distilled water if your anti-freeze strength is good enough to take it.

[anonymous-user]

There are certain ingredients (Google it) that when mixed in coolant gel up and could cause blockage. That is the reason. I would.invedtigaye why it is loosing coolant worringing about mixing is minor really.

[stevieturbo]

Mercutio said:

Relative newbie so go easy on me

Our Toyota Yaris (1.3, 2010) is low on engine coolant. So far, so normal.

I’ve purchased some Halfords general stuff by putting in my reg and the system “matching me” with the correct coolant

However all forum posts say “never mix engine coolant, always use the same one as manufacturer etc”

So question is this:

Can I safely “mix” and add this coolant?

Or do I need to take it to a garage and have the coolant “drained”, then fill it up with the new coolant as the only one?

Any advice very gratefully received!

if what you ahve been sold is correctly listed for the vehicle, then there should be no problem using it to top up.

Or just add water really, assuming there is still enough mix to prevent freezing etc in whatever climate you live.

[anonymous-user]

Don't add water op. The issue is that the lower boiling temp than coolantwill produce steam and over pressurise the coolant system.

[GreenV8S]

Thesprucegoose said:

Don't add water op. The issue is that the lower boiling temp than coolantwill produce steam and over pressurise the coolant system.

If it's a water based coolant then adding moderate amounts of water will not do anything harmful. If you dilute it far enough you will compromise the corrosion and anti-freeze protection.

[Mr2Mike]

Thesprucegoose said:

Don't add water op. The issue is that the lower boiling temp than coolantwill produce steam and over pressurise the coolant system.

That isn't an issue at all, raising the freezing point and reduction in corrosion protection are valid concerns if coolant is too dilute.

[Gary C]

Mr2Mike said:

Thesprucegoose said:

Don't add water op. The issue is that the lower boiling temp than coolantwill produce steam and over pressurise the coolant system.

That isn't an issue at all, raising the freezing point and reduction in corrosion protection are valid concerns if coolant is too dilute.

Yep, SG is talking bks, and as said the real concern is wher is the water going. I would Top up with water but monitor the level, if it falls again you need to think about finding the leak. Then drain and refil with new before winter once the leak has been resolved.
I did have a Toyota that kept loosing coolant due to a coolant cap lifting very light,

But don't keep topping up with water as the reduction in concentration will remove the main benefit of corrosion inhibitors (as long as it doesn't freeze)

Might be worth checking the dipstick for yellow 'Mayo' which is emulsified oil and would indicate an internal leak.

Edited by Gary C on Monday 28th May 01:07

Edited by Gary C on Monday 28th May 01:08

Edited by Gary C on Monday 28th May 01:10

[anonymous-user]

Gary C said:

Yep, SG is talking bks, and as said the real concern is wher is the water going. I would Top up with water but monitor the level, if it falls again you need to think about finding the leak. Then drain and refil with new before winter once the leak has been resolved.
I did have a Toyota that kept loosing coolant due to a coolant cap lifting very light,

But don't keep topping up with water as the reduction in concentration will remove the main benefit of corrosion inhibitors (as long as it doesn't freeze)

Might be worth checking the dipstick for yellow 'Mayo' which is emulsified oil and would indicate an internal leak.

Edited by Gary C on Monday 28th May 01:07

Edited by Gary C on Monday 28th May 01:08

Edited by Gary C on Monday 28th May 01:10

My experience is to the contrary especially on a 2 stage thermostat. Can over pressure the system always add a mix never water.

[Gary C]

Thesprucegoose said:

My experience is to the contrary especially on a 2 stage thermostat. Can over pressure the system always add a mix never water.

A small top up with a very small dilution is not going to make a difference. Biggest effect on raising boiling point will be pressure.

Not suggesting a big dilution but need to find out where the leak is, and if the system can't pressurise then that will lead easily to boiling.

[charlie7777]

Thesprucegoose said:

Don't add water op. The issue is that the lower boiling temp than coolantwill produce steam and over pressurise the coolant system.

What?

[Mr2Mike]

Thesprucegoose said:

My experience is to the contrary especially on a 2 stage thermostat. Can over pressure the system always add a mix never water.

The change in boiling point with typical anti-freeze concentrations suitable for the UK climate is very small, a few Celsius. You don't get a significant improvement in BP until the anti-freeze concentration is very high, and at that point you have already compromised the cooling due to the reduction in specific heat capacity. More detail.

[Dr Doofenshmirtz]

Just go to a Toyota dealer and ask them for a top up bottle. It's ready mixed and can be added straight from the can.
If it hasn't been changed since new in 2010 then get it flushed next service using the proper Toyota long life stuff. It's not that expensive.

You shouldn't mix DEX-COOL with run of the mill glycol ethanol antifreeze but Toyota don't use this in their systems. At the end of the day the stuff you got from Halfords will be fine, but as I said - if the stuff in there is 8 years old a flush would be beneficial if you're intending to keep the car.