I have a 98 chevy express van and it had been a very small leak would lose the entire overflow take after two or three weeks and the heat was a little weak but the van never over heated. I did some checking while the van was running and found it was a small drip of coolent from the water pump I put this in the overflow tank and went and started her up to my surprise almost immediately the dripping from the water pump stopped completely and the heat was normal again back to 142 degrees before it was only around 120 to 132 degrees it's been 6 months now and I had to do it again yesterday and same result the leakage stopped and the heat is more powerful than it was. I'm hoping this will continue to work because tarring into this kinda problem can cost 100's so this saved me time and money at least I hope may I will need to flush the system next year and I will definitely add this again and change the thermostat too.