Coolant – purge air or drain and change?

[otter148]

Hello,

I've got a Seat Leon Mk3 2014 1.4TSI ST.

I wasn't getting any hot air through my vents so tried purging air out of the system by removing the expansion tank cap and idling the engine for 15 minutes. This seemed to have worked a bit but the coolant fluid began to rise to the brim of the expansion tank so I stopped to prevent any of it overflowing.

Does any overflow matter or should I try removing some of the fluid first? I read that you probably need to top it up whilst purging, due to air escaping, not remove any!

Also, I noticed the coolant is not really pink/purple (G12/13) but pretty watery and not much colour. Is it worth draining the system and refilling with new coolant (I've got 5l of G40 from Halfords)?

Researching this there's loads of mixed stories about how easy/successful this is to do. And not much straightforward info on how to drain the system (which hose/s to remove etc)...

So maybe leaving what's in there is a safer bet and topping up if necessary?

I'm confident in changing the coolant but only with some clear, foolproof instructions!

Thanks in advance for any help.

Cheers

 

[RUM4MO]

For what it is worth, my personal advice would have been to buy a G65 product, which is what VW Group G12evo is and conforms to TL744 - L.

Anyway, from taking the official way of doing this from VW Group for the similar (hopefully) 2015 1.2TSI, engine, remove the main coolant circuit bottom radiator hose followed by the two charge cooler hoses which are at the opposite side of the car, remove the coolant fill cap before doing this, and allow all the coolant to drain out, then refit the hoses, pressure test the system to 1 atmosphere just to make sure that there are no leaks, fit a vacuum coolant refill kit and pull a vacuum on the system, then allow the new coolant to flood the system. Start the engine and run at moderate rpm until the cooling fan runs, top up coolant if necessary.

I'm making the assumption here that your engine is a EA211.

That is meant to be the only way to do this job and avoid ending up with trapped air in the system.

The other thing that I do, is to try to catch all the draining coolant and measure it so that I know how much MUST get loaded back in, as I don't currently have an air lock in the 2015 VW Polo coolant system, I also fit my pressure testing test to the cooling system while it is an ambient temperature and check apply a pressure of 1 atmosphere - and check to see how much the original coolant level gets depressed while that pressure is applied, doing that is another way to work out if you have refilling the system with coolant as trapped air can get compressed - coolant can't.

 

[nd-photo.nl]

Also remove the silica bag in the coolant expansion tank if its still there. See my howto here:

How to remove the Silica bag from the expansion tank

Follow this POV video if you want to remove the silica / silicat bag from the coolant expansion tank. They are known to rupture, where the silica beads will run through the coolant system and clog up the heater matrix. This will result in costly and unnecessary repairs. When you remove the...

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