A mechanic friend of mine told me that I have a crack in my engine block. I have all the signs. White smoke coming from the exhast, I can put antifreeze in my car and the next day its gone, there is antifreeze mixing with my oil, the car will suddently stop on me or not start at all, and there is too much oil in my car. He told me that block sealer would probably do a good job of keeping it together long enough for me to either pay for the repairs or get a new engine. My question is how long do block sealers work and what is the best one to use. All of your insight would be really great for me.