Coolant flush, what is capacity?

[92EcoDiesel Jetta]

I am replacing the coolant witth G12 and do not have my Bently with me. First, what's the capacity of a 1.6? After engine was warmed up, I pulled the lower hose at the water pump and also hose at the cyl head flange and let it drain. I did not pull the T-stat. Too much of a PITA. I then pour hot water down the upper hose and the expansion tank to flush the rad and head  out. Put the hoses back, fill with hot water and take for a drive to warm up the engine and repeat the above. I did this 3 times total and the water is coming out clear. Even though the engine was warmed up, I was not sure if the T-stat was fully open to drain the block completely by the time I pulled the hose at the T-stat (the hose was pulled within 5 minutes after stopping to drain the system). How do I know if block was fully drained if I did not pull the T-stat? I guess I can measure what came out. How much is in the block if the T-stat was closed? Is it more than 50%?

[RadoTD]

It's about 6L total, probably around 2L in the block, 2L in the rad and 2L everywhere else, including heater core, random hoses etc

I would've just dropped the tstat, but then again, I've done it enough times it's only about a 20min job to get it out 

As long as you're anywhere near 50% coolant, you'll be fine. I actually only run about 2L of coolant, so about a 66/33 mix. If you pull off the head flange, empty the heater core, pull the top hose off the rad etc, you'll be able to fit in close to 2L of coolant

I wouldn't run G12 though; no advantage to it and some cars start leaking if it's swapped in. Stick with G11

[92EcoDiesel Jetta]

I measured what came out, at least 3/4 of a gallon (2.8 liters), probably more with spillage unaccounted for.
How do you drain the heater core? I thought G12++ is backwards compatible to the older VW coolants? I hope mine will not leak.

[RadoTD]

Yes, they are all compatible. I asked my parts guy at the stealership if it would help me any if I went to G12 or G12++, he said no and that some people had leaks start when they swapped it. Might just be unrelated though... I don't see how that would happen to a cooling system in good condition. If you already have the coolant, put in whatever you have. G12 cannot be mixed with G11, but G12++ can be mixed with it... just in case you ever run into that.

To drain the heater core, I pull the two hoses off near the block, stick a hose to the one and flush water through it, then hold them down until water stops flowing out. There will be a bit of water left, but nothing significant.

At least 3/4 gallon sounds about right, topping that off completely with coolant will be more than enough!

[92EcoDiesel Jetta]

Did something different this time. I refuse to pull the T-stat to flush the coolant damm it!
Why? Because it is not leaking there now and I know if I pull it a leak will develop. 

Did another flush with water and went for a drive to get the engine good and hot, pulled it and let it idle till the fans come on, shut engine off and pulled fan connector so I don't get hit by the blades. Long sleeve shirt so I don't get burned by the hot hoses and went in from the top and un-did the hose clamp to the T-stat housing. The pressure from the system pushed the hose out (no pulling necessary) and it drained.  I then loosened the expansion tank cap but no more water came out of the T-stat housing. I started the engine and ran it for 2 seconds, more water came out of T-stat housing. Did that 2 more times  (ran engine for 2 secs), each time more water came out.
Filled system via the upper hose first then via the exp tank and was able to put in a total of 5.3 liters and used up both 1.5 liter bottles of G12++.

To recap- I was able to drain most of the water out without pulling the T-stat. What little water remained was likely in the heater core, which I did not try to drain.

[RadoTD]

Haha, that's actually a pretty cool idea! I'd be scared to drain a hot cooling system but it sounds like that did the trick!

[burn_your_money]

I've heard that draining a system with hot coolant is bad for the engine. I suspect it relates to the headgasket but I don't know. I know that you don't want to add cold coolant to a hot or warm engine.

[DCC]

I've heard that draining a system with hot coolant is bad for the engine. I suspect it relates to the headgasket but I don't know. I know that you don't want to add cold coolant to a hot or warm engine.

Last time I flushed the coolant in my car I tried not to completely take out the hose, so I could add water via expansion tank at the same rate it was comming off and lessen the thermal shock (if any). It actually turned out good, and kept adding water until it was clean.

[92EcoDiesel Jetta]

BYM, I'd like to hear more about draining coolant hot is bad for the engine/head gasket. It is no different than if a radiator hose blows and you lose the coolant. Now if you keep driving after the hose blows, I can see that's not good.

Rado, draining the coolant hot like I did on a healhty engine is ok if you take certain precautions.

1. Don't be under the car. Work from above.

2. Wear rubber gloves, long sleeve shirt and goggles.

3. Don't do it if you have abnormal  coolant system pressure . E.g. overheated and boiling coolant,  combustion gas leak into cooling system.

[burn_your_money]

Unfortunately it's all I know about it. It may be because service manuals usually tell you to drain it cold so people have assumed it to be bad while the manuals may just say that for safety reasons.