Proper mixture for G12 Coolant, ALH?

kennethsime

Veteran Member
Joined
Oct 29, 2010
Location
California
TDI
2004 Jetta Wagon GL TDI 5-Speed Baltic Green
Hi everyone,

Replaced the thermostat the other day and got everything back together alright, no leaks or anything, but I ended up with only 1.5l of G12 and mixed that with a gallon or so of distilled water to fill up the coolant system as a temporary fix. Picked up a gallon of G12 today, want to get the mixture right. Do I have to do a complete drain, and do a pre-mix to ensure my 50/50 blend? What is the quickest way to do this? It seems like most of the G12 hasn't cycled up into the coolant expansion tank (which is mostly water with some G12 mixed in). I originally put in a 50/50 mix, then topped off several times with distilled water. Knowing this, is there any point I can drain which would retain my 50/50 towards the bottom or do I have to re-drain completely again (was kind of a pain in the butt to do the hoses from the oil cooler and the lower intercooler pipe).

On the mixture, I know my owners' manual recommends not less than 40% and not more than 40%, and most tutorials will recommend 50%. The detriment of too little being corrosion and not enough of a cooling effect? The detriment of too much being...? Too viscous? I've read that some will increase the water in summer months although this seems silly.
 

tditom

Top Post Dawg
Joined
Sep 5, 2001
Location
san antonio & austin
TDI
formerly: 2001 Golf GL, '97 Passat (RIP) '98 NB, '05 B5 sedan
Try to extract 1.25qts of the current coolant mix in your engine and replace that with straight G12. You'll be close enough to 50-50.
 

jcrews

Top Post Dawg
Joined
Jul 28, 2007
Location
Round Rock, TX - VCDS
TDI
All gone
70/30 yields maximum freeze protection (not really an issue in most places). ALH has a
6L system so it is convenient to dump the whole 4L bottle in your mixing container and adding 2L of water (which is roughly 66/33)

The cooling system is good enough to deal with up to 70/30 - since heat transfer efficiency does decrease with more ethylene glycol. Pure glycol wouldn't work well since the water is the main heat transfer agent.

Pure ethylene glycol has a freezing point not much lower than water (-12C).

Too little (below 40/60) mostly has to do with dilution of anticorrosive additives. In real, practical terms, it doesn't matter as long as it's somewhere in the range of 40-70% glycol.
 
Last edited:

kennethsime

Veteran Member
Joined
Oct 29, 2010
Location
California
TDI
2004 Jetta Wagon GL TDI 5-Speed Baltic Green
70/30 yields maximum freeze protection (not really an issue in most places). ALH has a
6L system so it is convenient to dump the whole 4L bottle in your mixing container and adding 2L of water (which is roughly 66/33)

The cooling system is good enough to deal with up to 70/30 - since heat transfer efficiency does decrease with more ethylene glycol. Pure glycol wouldn't work well since the water is the main heat transfer agent.

Pure ethylene glycol has a freezing point not much lower than water (-12C).

Too little (below 40/60) mostly has to do with dilution of anticorrosive additives. In real, practical terms, it doesn't matter as long as it's somewhere in the range of 40-70% glycol.
Yea, I would think that more coolant = more better, but I guess not.

I filled up again yesterday, the mixture in the expansion tank had gotten a bit more pink (more what i'm used to seeing) but I sucked it dry with the Pela and filled with straight G12. I also found out I already had a gallon of G12 in the garage (paid $25 at the dealer, whoops). I've never had a problem with overheating (knock on wood) and I'm going to call it good. Fit about a liter of straight G12 in.

Man I love the new thermostat, can't believe I waited this long.
 

jasonTDI

TDI GURU Vendor , w/Business number
Joined
Apr 26, 2001
Location
Oregon, WI
TDI
20' RAM 3500 CCLB dually HO/Aisan. 2019 Cherokee 2.0T
FWIW to EVERYONE here. G12 is N.L.A. except for the last bit dealers have. It has been superseded by G13. Silicates back in, back compatible with G12.

Also, if you are STILL running G11 you'll need to switch out unless you can find some of the Pentosin brand as that has been discontinued.
 

kennethsime

Veteran Member
Joined
Oct 29, 2010
Location
California
TDI
2004 Jetta Wagon GL TDI 5-Speed Baltic Green
FWIW to EVERYONE here. G12 is N.L.A. except for the last bit dealers have. It has been superseded by G13. Silicates back in, back compatible with G12.

Also, if you are STILL running G11 you'll need to switch out unless you can find some of the Pentosin brand as that has been discontinued.
Yea, the dealer gave me G13 when I asked for G12.
 

jasonTDI

TDI GURU Vendor , w/Business number
Joined
Apr 26, 2001
Location
Oregon, WI
TDI
20' RAM 3500 CCLB dually HO/Aisan. 2019 Cherokee 2.0T
I was thinking that....Bet they will have a hard time selling it in some parts of the world.
 

n1das

TDIClub Enthusiast, Veteran Member
Joined
Jun 11, 2002
Location
Nashua, NH, USA
TDI
2014 BMW 535xd ///M-Sport, 2012 BMW X5 Xdrive35d, former 3x TDI owner
70/30 yields maximum freeze protection (not really an issue in most places). ALH has a
6L system so it is convenient to dump the whole 4L bottle in your mixing container and adding 2L of water (which is roughly 66/33)

The cooling system is good enough to deal with up to 70/30 - since heat transfer efficiency does decrease with more ethylene glycol. Pure glycol wouldn't work well since the water is the main heat transfer agent.

Pure ethylene glycol has a freezing point not much lower than water (-12C).

Too little (below 40/60) mostly has to do with dilution of anticorrosive additives. In real, practical terms, it doesn't matter as long as it's somewhere in the range of 40-70% glycol.
What jcrews said.

70/30 (70% G12 / 30% water) gives the best freeze protection. It also gives the best boilover protection in hot weather. The 70/30 ratio allows you to add just water if you sometime later need to top the level off to make up for any lost coolant and stay in the 40-70% G12 range.

As long as you stay in the 50/50 (50% G12 / 50% water) to 70/30 (70%G12 / 30% water) you should be fine.

Good luck.
 
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