draining coolant to replace thermostat then reusing?

**bk.bas99** · 15-12-2014,04:25 PM

Since I have removed the alternator to repair thought it would be a good idea to replace the thermosat as VCDS has always shown it as peaking out at 84 and consumption has always been a bit less than everyone else seems to get (av 43). However as I have just had a new radiator and hoses with new G12 coolant is it possible to drain the system without loosing the coolant. I can pull the bottom hose from the radiator to drain that (it's not in the lock carrier position so can't get to the tap) but how do I drain the block...is there a way or do I just drain the radiator then remove the thermostat housing and write off the coolant in the block?

**NickPicks** · 16-12-2014,10:35 AM

Personally, I'd just remove the thermostat housing, wait until coolant stops coming out, fit the new stat, then refill with new G12++, bleed the system as required, then wash the old coolant off the driveway with a hosepipe.

Coolant isn't expensive enough to worry about capturing it to re-use (in a clean container with a clean hosepipe), or environmentally bad enough to worry about washing down the drain.

**bk.bas99** · 16-12-2014,01:19 PM

It's not the cost of the coolant, it's the fact that I now have the alternator off and want to change the stat defore I put it all back together but am miles away from anywhere that I can buy G12 from, want to save enough to be able to drive far enough to buy rerplacement. Yes I know, didn't think it through. Alt was shot so was tackling that, then decided to change stat at same time as had bought one from VW a while ago due low temp reading. Thought I would try to drain radiator (and catch coolant) then do same with collant hose to stat...or should I just pull coolant hose to stat and catch as much as I can? Not sure how much of the 6L total would come out if radiator not drained?? !

**zollaf** · 16-12-2014,01:22 PM

pull stat, release coolant. don't bother trying to catch it. fit new stat. fill with water. drive to antifreeze shop, buy antifreeze. drive home, let car cool, drain water, add antifreeze. job done and you have give the system a flush as well, without even trying to

**bk.bas99** · 16-12-2014,01:47 PM

yes that's my default fall back! How much coolant will come out when I disconnect the stat, any idea?

**zollaf** · 16-12-2014,01:48 PM

not much. its towards the top .

**bk.bas99** · 16-12-2014,02:56 PM

But won't the water in the rad flow out of the lower hose when it's disconnected from the thermostat housing?

**zollaf** · 16-12-2014,03:29 PM

which engine ?

**bk.bas99** · 16-12-2014,03:51 PM

1.9 TDi AWX

**NickPicks** · 16-12-2014,04:01 PM

It'll have to flow upwards, so you'll only lose the water in the radiator above the level of the thermostat housing. I'd think you'll probably lose about 1/4 of the entire coolant.