A quick check for gasket leaks is to open (TAKING appropriate precautions not to burn the bejabbers out of yourself in the process and/or getting a face full of steam etc.) the radiator after the vehicle has warmed up and see if there is any discoloration in the coolant, and/or any smell that is not like normal coolant.<br><br>Also, sometimes the radiator may be venting (due to blow by pressure) even though the temperature is not really abnormal. <br><br>An additional check it to look at the oil on the dipstick, if it starts changing from a nice oily color (varies on how long its been used) generally a black color to a coffee with milk color, you can figure on having water in you oil from the coolant. Another cue would be a rising oil level even though you haven't added any, and/or a suprisingly slow use of oil in an engine that typically can be counted on to need X amount added every X amount of miles or X amount of time.<br><br>My experience is that the block sealer is generally added after the symptoms make their presense known. Do not figure on it being a permanent fix though. Just a way to get down the line to make the proper repairs. <br><br>I concur with the mystery of newer engines and related troubleshooting/repair work. <br><br>Regards,<br>Comanche7