Proper coolant flush

[llmercll]

Hello, I am wondering what a proper coolant flush consists of. Do I just drain, fill up with distilled water, run engine with heater on, and then drain once more? We've been using dexcool in our 03 jetta and the radiator needs to be replaced. I am just contemplating whether or not to flush and fill with g12 or just fill with dexcool. Thank you!

 

[The_Nuke]

The method of flushing largely depends upon the system's current state. If it has not been maintained well or poorly over its previous life, you'll want to do the most aggressive flush you are comfortable doing or able to do, e.g. drain coolant, refill with water and a chemical flush, drive a couple days, drain, fill, drain, fill, until no color in what comes out. Then fill with proper coolant/water mix. If the system has been well maintained over its previous life, you don't necessarily have to do a flush at all. Just drain the system and refill with proper coolant/water mix. You say your radiator needs to be replaced, but you don't say why. Is it clogged, leaking, or what? If it's clogged or doesn't flow properly, you can take that as a sign that the system has been maintained poorly and adjust your maintenance tasks accordingly.

 

[ZZman]

If you are going to do it why not do it all the way? Buy a flush additive and lots of distilled water.

 

[khittner]

In the Rust/Salt Belt (like NY), a common failure mode is via external corrosion of the fins, causing them to detach from the tubing, and resulting in the loss of heat transfer capacity without any leakage or plugging up, regardless of maintenance routine.

 

[Donald]

Why Dexcool in a VW? I would never use Dexcool in a vehicle unless it came that way from factory. I would flush with a mild cleaner, then distilled water and then refill with a VW approved coolant or G-05 or Peak Global.

 

[barkingspider]

Just flush w distilled water until clear then go w 50/50 ratio of whatever coolant u like best.

 

[SHOZ]

I usually drain, fill with water and a cleaner. Drive a day or so. Drain and fill with distilled or demineralized water. Drive so all the coolant is good and hot. Drain and fill with a gallon of 70/30 as you cannot get all the water out. Then top off with 50/50.

 

[maxdustington]

Because Dexcool has the same chemistry as G12 or whatever they upgraded it to. You can get dex anywhere, G12 is dealer only. NAPA has universal euro coolant that is also suitable.

 

[llmercll]

Ok, I think I will flush it and then add g12. Do I really need a chemical cleaner? Is it ok if I put in one gallon of concentrate and one gallon of water or do I need to do this in a bucket outside the vehicle?

 

[The_Nuke]

Originally Posted By: llmercll

Ok, I think I will flush it and then add g12. Do I really need a chemical cleaner? Is it ok if I put in one gallon of concentrate and one gallon of water or do I need to do this in a bucket outside the vehicle?

The chemical cleaner isn't a necessity, but if you have never changed the coolant or it comes out in really bad shape, it wouldn't be a bad idea to use a cleaner to clean things up a little. You can mix the coolant and water before, during, or after...basically mix it any way you wish. The end result needs to be that once the car is running and the water pump is pumping, the liquid being pumped is mixed to the correct ratio. As long as that is achieved, you are golden.

 

[llmercll]

Ok thank you for the advice. I'm in NY and it's getting cold here. If I use distilled water for the flush and it's 40 degrees or so I don't risk it freezing right away if I put the water in and immediately go for a drive right?

 

[The_Nuke]

Originally Posted By: llmercll

Ok thank you for the advice. I'm in NY and it's getting cold here. If I use distilled water for the flush and it's 40 degrees or so I don't risk it freezing right away if I put the water in and immediately go for a drive right?

No, you will be fine. In fact, if you have a Walmart close by (or any other store that sells automotive trinkets), you can make part of that drive going there and purchasing one of those little suction-bulb testers for antifreeze to use with yours. Before using it, you only need to make sure the engine has reached normal operating temp and begun circulating the coolant/water mixture throughout the block and radiator. That will mix it all up right nicely, and you will be good to go from there on out. But with that tester, you can actually determine where that specific mixture in your vehicle will be in danger of freezing (and boiling over). It's quite an ingenious little tool for as simple and inexpensive as it is, I wouldn't trade mine for a moving box full of monkeys!

 

[nthach]

Originally Posted By: Donald

Why Dexcool in a VW? I would never use Dexcool in a vehicle unless it came that way from factory. I would flush with a mild cleaner, then distilled water and then refill with a VW approved coolant or G-05 or Peak Global.

Dex-Cool is similar to G12 coolant, the Germans for the most part were OK with 2-EHA as the organic acid. Mercedes was all about G-05 but recently switched over to G-48 which is also used by BMW and Tesla. G-48 is a low-silicated HOAT using 2-EHA instead of sodium benzoate. If the drained coolant has no visible signs or dirt or oil more than a residual slick like droplets or milkshakes/mayo-like buildup, I'd skip the flush and fill'er back up with Dex-Cool. If you want to go back to the factory magenta G12, a flush with water wouldn't be a bad idea. What motor do you have in that A4 Jetta - ABA 2.0, the 1.8T or the VR6? I liked those generation of Golf/Jetta, not the greatest reliability but they were a huge upgrade over the A3. I've always liked how they looked.

 

[admzn]

I have the same generation Golf. It is a pretty decent car, some little annoyances, but otherwise it has been reliable for me (and my brother before me). The radiators are notorious for leaking. I had to replace mine. First time with a used one and then it leaked again, so I bought a new one. I always used the proper VW coolant, it isn't that much more and is nice peace of mind. I have never flushed it but have done 3 drain/fills in the past 4 years so probably alright, lol.

 

[nolesfan]

FYI, G-12 and G-13 are not dealer only coolants. You can buy them online all day long and can usually have them on your doorstep within a couple days at most. I just bought some G-13 for my GLI since I'm having to top off a few ounces per year. Cost was $12.99 or something for a 1.5 liter bottle of Vaico and free shipping since my order went over $49.99. Since these are concentrates, that nets me 3 liters of coolant for $12.99 (mixed with distilled water). Not too shabby in my book! I understand it could be a cost thing for most people, but just throwing it out there... Mike