Cooling system change and temperature

[E38Ross]

When changing the coolant does it have to be stone cold or can it be done when warm? If, for example, I have to drive somewhere I have the space etc to do it (and by this time the engine including oil is fully up to tenp) roughly how long would I need to wait until it cools down enough until the change could be done?

Thanks chaps.

[E30M3SE]

I'd probably be leaving it a hour or so, if its fully up to temp.

ETA, open the bonnet when you get to where you're going and remove the rad cap/expansion cap after 10 minutes or so, does depend on the outside temp, the colder it is the quicker it will cool down.

Edited by E30M3SE on Sunday 17th June 07:13

[redtwin]

Not advisable to add cold coolant to a hot engine.

[E38Ross]

redtwin said:

Not advisable to add cold coolant to a hot engine.

Yeah, just curious how long to leave it until it's safe. The car has a digital temperature read out and i'm guessing if it's below 40-50deg it should be ok...?

E30M3SE said:

I'd probably be leaving it a hour or so, if its fully up to temp.

ETA, open the bonnet when you get to where you're going and remove the rad cap/expansion cap after 10 minutes or so, does depend on the outside temp, the colder it is the quicker it will cool down.

Edited by E30M3SE on Sunday 17th June 07:13

Thanks E30M3SE, guessing taking the rad cap off with bonnet open will allow it to cool quicker?

Thanks chaps!

[4keymonsta]

If that is what you are worried about... boil the kettle a few times?

[redtwin]

Personally I would wait until the coolant exiting is the same temp as the coolant entering, but that is because I have heard enough horror stories about cracked engine blocks etc.

[tgr]

If you open the cap on the expansion tank when the engine is hot plenty will flood out, because the coolant has expanded. Wait until it's as cold as possible, ideally tap water temp

[NiceCupOfTea]

It goes without saying that you should be very careful when you open the radiator cap - crack it off very slowly with a rag to avoid scalding your hands. Eye protection too.

[BOBTEE]

NiceCupOfTea said:

crack it off very slowly with a rag

If you can't find an old rag just use a sock

Assuming the car is up to normal operating temperature when you arrive at your service area, I'd give it half an hour or so to cool to a point where you can work on it, just be sensible and don't position yourself where coolant is likely to splurt out. I'd say by the time you've drained the old stuff out and refixed all the pipework etc you'll be ok to refill straight away, it's unlikely to do any damage.