For those reading later, the really interesting bit for me personally starts at 6:48 on this video. If you are just doing a coolant refresh, and NOT flushing the whole system, this bit, starting at 6:48 is how you do the job.. You do not need to make a mess of your shop vacuum, undo major hoses, or let the coolant splash all over the front subframe while it drops into a pan beneath the car. You do not even have to remove the lower engine cover. The coolant goes neatly into a bucket, when you connect a section of tube running from the top of the radiator, over the front bumper and into a nearby bucket. If you attach a clear 1/2" OD tube right in the location shown and PLUG THE LINE that you removed from that 8mm nipple on the radiator fitting, the suction on the removed line will be blocked. Use a clear flexible tube about four feet long, and drop the free end in a bucket. When you start the engine, old coolant will flow from the radiator line under light pressure from the water pump. New coolant, which you pour into the reservoir will be pulled, by suction, into the engine. In this manner you can rapidly extract 4 to 5 liters of coolant out of the cooling system at the top of the radiator, and introduce the same amount of new coolant into the engine, through the reservoir. When you are done, my suggestion is that you then drive the car for a while, until the new coolant is completely mixed with whatever original coolant remains. After everything is completely mixed, then TEST the acidity of the coolant with a test kit, such as the Phoenix Systems 8006-B Double-Ended Brake Fluid + Coolant Test Strips, to see if the acidity is low enough for your needs. Acidity of 5 needs replacement 6 is cusp, and 7 is okay. 8.2 is the pH of brand new G12 50/50 pre-mix.. If the acidity is still too high, after one extraction, then do one more extraction of 4 or 5 liters of old engine coolant, while pouring the same amount of new G12 pre-mix into the reservoir. These changes will take you about 15 minutes each. The water pump in the engine does the work for you. You get about a 60% change of the coolant, each time you do this. Total engine capacity for coolant is said to be around 7 liters. Best of all, when you use this approach it is not necessary to bleed the system afterwards, because you never let any air into the system. You block the suction on the line that emerges from the radiator, when you attach the new waste line to you bucket. No air gets into the system with this approach. Before I executed this procedure, I had an acidity of my coolant of pH 5.5, using a Coolant Test Strip. This is too acidic and the coolant needs to be replaced with a pH this low. The pH of brand new, 50/50 mixed G12 coolant is 8.2. After removing 5 or 6 liters of old G12 coolant in a 50/50 ratio, and replacing that with new G12 50/50 mix, I have an acidity of 7. Since 8.2 is perfect, this is a big improvement for 15 minutes of work. I did the pH test after I had driven the car for a while, in order to get a good mix of new and residual, old coolant. Tomorrow I will do one more cycle of 4 liters out, 4 liters in, to get a little closer to 8. If you are not flushing out a dirty system, and simply want to bring the pH of your coolant back to a good working level, the method described at 6:48 is where you want to start. Pull out old coolant at the same time you add new G12 coolant, then drive the car for a while and then test. If the pH is 6, do it one more time, 7 is a good working number. 8 is perfect, as good as brand new, G12 coolant / water mix gets.. Just my thoughts Pete, thanks VERY much for this fine video.
Hi, you say that at 6:48 is not the way to do a full flush of the system, just a way to do a refresh. If this is true, how would you do an entire reflush of the whole cooling system? TIA
Pete, at 7 mins in your video you show what looks to be the easiest and most efficient way to flush the coolant water in via a hose, drain out running the engine and a tube from the top entry to the top of the radiator. Looks great as the system really flushes until the water is clear then refill with VW coolant. Am I missing anything? Thanks for sharing.
Hello Pete, thank you for this very informative video! Do you know if this method is effective for flushing and cleaning the heater core and intercooler?
If you have the heater set to high then yes, this process should also flush the heater core. The intercooler however is an air-to-air intercooler so there is no coolant involved.
You would think so but, no, nothing in the way of a drain. What is worse, is that is no way to drain the bottom half of the radiator on a TDI without actually removing the entire radiator and turning it on it side. I am not joking. The lower hose connects in the middle of the side of the radiator. Not at the bottom unlike just about every other water cooled car on the planet.
LOL. The 'bottom' radiator hose is not at the bottom of the radiator. It is halfway up the side of the radiator. And you do not 'just remove it'. Some people remove the right front wheel, the fender liner, and go in from that side.
For those reading later, the really interesting bit for me personally starts at 6:48 on this video. If you are just doing a coolant refresh, and NOT flushing the whole system, this bit, starting at 6:48 is how you do the job.. You do not need to make a mess of your shop vacuum, undo major hoses, or let the coolant splash all over the front subframe while it drops into a pan beneath the car. You do not even have to remove the lower engine cover. The coolant goes neatly into a bucket, when you connect a section of tube running from the top of the radiator, over the front bumper and into a nearby bucket.
If you attach a clear 1/2" OD tube right in the location shown and PLUG THE LINE that you removed from that 8mm nipple on the radiator fitting, the suction on the removed line will be blocked. Use a clear flexible tube about four feet long, and drop the free end in a bucket. When you start the engine, old coolant will flow from the radiator line under light pressure from the water pump. New coolant, which you pour into the reservoir will be pulled, by suction, into the engine.
In this manner you can rapidly extract 4 to 5 liters of coolant out of the cooling system at the top of the radiator, and introduce the same amount of new coolant into the engine, through the reservoir. When you are done, my suggestion is that you then drive the car for a while, until the new coolant is completely mixed with whatever original coolant remains. After everything is completely mixed, then TEST the acidity of the coolant with a test kit, such as the Phoenix Systems 8006-B Double-Ended Brake Fluid + Coolant Test Strips, to see if the acidity is low enough for your needs. Acidity of 5 needs replacement 6 is cusp, and 7 is okay. 8.2 is the pH of brand new G12 50/50 pre-mix..
If the acidity is still too high, after one extraction, then do one more extraction of 4 or 5 liters of old engine coolant, while pouring the same amount of new G12 pre-mix into the reservoir. These changes will take you about 15 minutes each. The water pump in the engine does the work for you. You get about a 60% change of the coolant, each time you do this. Total engine capacity for coolant is said to be around 7 liters.
Best of all, when you use this approach it is not necessary to bleed the system afterwards, because you never let any air into the system. You block the suction on the line that emerges from the radiator, when you attach the new waste line to you bucket. No air gets into the system with this approach.
Before I executed this procedure, I had an acidity of my coolant of pH 5.5, using a Coolant Test Strip. This is too acidic and the coolant needs to be replaced with a pH this low. The pH of brand new, 50/50 mixed G12 coolant is 8.2. After removing 5 or 6 liters of old G12 coolant in a 50/50 ratio, and replacing that with new G12 50/50 mix, I have an acidity of 7. Since 8.2 is perfect, this is a big improvement for 15 minutes of work. I did the pH test after I had driven the car for a while, in order to get a good mix of new and residual, old coolant. Tomorrow I will do one more cycle of 4 liters out, 4 liters in, to get a little closer to 8.
If you are not flushing out a dirty system, and simply want to bring the pH of your coolant back to a good working level, the method described at 6:48 is where you want to start. Pull out old coolant at the same time you add new G12 coolant, then drive the car for a while and then test. If the pH is 6, do it one more time, 7 is a good working number. 8 is perfect, as good as brand new, G12 coolant / water mix gets..
Just my thoughts Pete, thanks VERY much for this fine video.
Very good information. Thank you for your detailed addition. Love it!
Hi, you say that at 6:48 is not the way to do a full flush of the system, just a way to do a refresh. If this is true, how would you do an entire reflush of the whole cooling system? TIA
Pete, at 7 mins in your video you show what looks to be the easiest and most efficient way to flush the coolant water in via a hose, drain out running the engine and a tube from the top entry to the top of the radiator. Looks great as the system really flushes until the water is clear then refill with VW coolant. Am I missing anything? Thanks for sharing.
Hello Pete, thank you for this very informative video!
Do you know if this method is effective for flushing and cleaning the heater core and intercooler?
If you have the heater set to high then yes, this process should also flush the heater core. The intercooler however is an air-to-air intercooler so there is no coolant involved.
Isn’t there a drain? I have a mk4 golf and there’s a tap by the bottom rad hose.
Nope. Unfortunately there is no coolant tap/drain.
You would think so but, no, nothing in the way of a drain. What is worse, is that is no way to drain the bottom half of the radiator on a TDI without actually removing the entire radiator and turning it on it side. I am not joking. The lower hose connects in the middle of the side of the radiator. Not at the bottom unlike just about every other water cooled car on the planet.
Just remove bottom rad hose 😂
You don’t understand how complex the vw system is, that only gets about 1l out via the bottom hose
Agreed.
LOL. The 'bottom' radiator hose is not at the bottom of the radiator. It is halfway up the side of the radiator. And you do not 'just remove it'. Some people remove the right front wheel, the fender liner, and go in from that side.