I guess I will start at the beginning. I was useing my YM1700 the other day gradeing my hill, that goes to my driveway. It was 94 degrees, and after a while it started to make a lot more noise. I thought it must be hot, so quit and came back to the house, as I came it quieted down, by the time I got to the house, about 1/5th mile, it sounded OK. I found out the bulb to the temp. was burnt out. I replaced it and I thought I would change the antifreeze at the same time to get the 30/70 I should have as didn't know what it was. After I flushed it out good and changed it, I ran it for about 10 minutes or so and checked it to see if it was full and all. But I found air bubbles coming out of the overflow tube. Is this normal? It seems to be runing allright and no oil in water or water in oil. So am wondering if I have a problem or not.