Giving it a shot. My VW Golf Sportwagen has an intermittent leak from the joint between the water pump and thermostat housing. VWs really have coolant leak issues/super common. It's under warranty but they already pressure tested it and said no-go b/c it didn't leak during the test. You can clearly see the white dried coolant... oh well. I'm closing in being out of warranty, have heavily modified it, and at this point I figure for $6 it's not going to hurt it. Added it to the expansion tank cold per LM's instructions. Got it up to temp, turned the heat on, and drove it around. We will see. 1 can treats 2.5L which is the volume of coolant that VW says I have. At some point the intake manifold is coming off to do a walnut blast/carbon cleaning and maybe replacing it with an Euro MPI manifold for a "stage 3" upgrade. With VW's track record of these parts on the MQB 4-bangers, I'd replace the water pump/therm housing anyway. I'll report back after a few weeks. This stuff is supposed to be "new gen" and can actually be used as a preventitive per LM. Why not. A white colored stop leak is strange to me and you can actually see what appears to be green colored dots in the goo.