Just did coolant change - didn't need 8L per Penrite's info

[Finance_Analyst]

As my GTi is coming onto 3 yrs old in May, I decided to do a full radiator flush and new coolant. Scored the latest G12++ Penrite stuff (6yr/350,000km) at the Repco Boxing Day sale. Couldn't get full concentrate so had to buy premix x2 as Penrite said it is 8L all up.

Took it to a specialist radiator guy who had looked after all my cars in the past and interestingly, he wasn't able to completely drain the whole system - there was not another plug to let it all out or something (but he got the bulk of the coolant out). Then he refilled it with the premix and it only needed 4.7L all up. Was told that it is quite normal that newer cars don't require as much coolant (my old SLK Merc took 7.5L or so), plus there was probably some excess water left which was unable to be released. I filled it within the parameters in the manual is all good there.

Question is - has anyone experienced something similar to the above, as in their car didn't need much coolant?

I could see that this car was harder to work on given the limited space in the engine bay so kudos to him for getting it done!

[gazzmo]

Yes I can confirm that there is no way to extract all the old coolant unless you use a vacuum system as the radiator retains around 1.5 litres, in the process of changing my timing belt and water pump and was able to extract around 5 litres. The G12 coolant has a life of 5 to 6 years and is only rarely changed in total, normally the concentration is checked and if needed adjusted with additional coolant.

[Transporter]

Well, the Penrite says as per their note 1199 "Total Flush Required". Penrite Australia - NetLube

Which means, you have to remove all the coolant from the cooling system. A good mechanical workshop should have the equipment that is able to evacuate the old coolant and then vacuum fill a new coolant in. I wouldn't be very happy having a 1/2 of the original coolant in mixed with the aftermarket brand and it doesn't matter that they say it's manufacturer approved.

In your situation now, it would be much better to use the VW coolant, wouldn't you agree?

[gazzmo]

I agree the best solution is to do a total evacuation of the old coolant, I am going to do a back yard job and blow/pressurise the radiator to remove the balance as the other solution is to remove the radiator no small task At least the motor is fully drained and I can clean the reservoir so much fun work on my dub.

[Finance_Analyst]

Thanks.

The guy did flush with a high pressure hose then a air pump so I imagine the bulk of it got out. From my experience the dealers (any car not just VW) only drain the coolant and not full flush. I think it is weird that VW design it in such a way you cannot fully drain unless you dismantle the radiator. - there was a BMW 320i E90 getting the same job done yesterday and that seemed to be no problem.

[Transporter]

On average it takes around 1 hour to change the coolant. I usually use 20L of water to completely flush the cooling system and then use coolant concentrate at 1/2 of the cooling system capacity and top up with distilled water. On some models removing the thermostat/heather hose is necessary to get all the coolant out, then you have to bleed the system so you don't overheat the engine. Depending from model to model to change the coolant doesn't have to be a DIY job. How do you dispose the coolant? Do you catch all the water when flushing it? Remember any fluid that went in the engine and comes out is contaminated and could be very toxic to the environment.

Also, the air pockets that you could leave in the cooling system will create the hot spots and have a potential to damage the engine.

[nat225]

so, what is the factory flush interval btw? 4 yrs / 60,000 km?

[Transporter]

so, what is the factory flush interval btw? 4 yrs / 60,000 km?

I would change the factory coolant after 5 years, especially if no top ups were required. And would always stay with VAG coolant, there is really no need to go for the alternative like Penrite. If you're somewhere remote, you can always buy 1,2 or 3 bottles of the coolant from the dealer and have it handy should the need arise. But, for once in a year or two small top up on a new car distilled water will be sufficient, then if you need to top up much bigger amount, the coolant availability shouldn't be much of the concern, to find and repair the coolant leak is, which for many means a trip to the workshop anyway.
I don't recommend using the Penrite coolant for top ups, where mixing two different coolant brands even goes against Penrite recommendation. If your mechanic is saying you can mix them or the partial drain and refill is OK, then you're better of keeping the factory coolant in, especially if the car is only 3 years old.

[Diesel_vert]

so, what is the factory flush interval btw? 4 yrs / 60,000 km?

No drain interval is specified - the coolant level and concentration rate is just checked, and adjusted or topped up as necessary.

The additive package of coolants based on organic acid technology or OAT (such as VW G12 & G13 coolants) have very slow depletion rates compared to traditional additives.

If pressed for figures, 5 years or 250 000 km is a common drain interval for such coolants.