Hi, i recently bought a LS430 2003 model, everything is fine until i went for a long trip. After riding about 150 km when i stopped in traffic signal the heat signal starts raising from half way level. I suddenly turned off the engine and after about 2 minutes i turned on. But heat signal was normal. Below half way line. Anyone know whats exact issue. The mechanic told ke that he need to change engine head. Can some one pleass help

 

Why turn the engine off? If it gets into the red zone, then turn the engine off. Otherwise it is just doing what it needs to do.
However, it does sound like your cooling system needs to be investigate by a mechanic.

 

Find a new mechanic. If your car is in fact overheating, changing the head won't fix the root cause of the problem. Make sure your antifreeze level is full and your cooling fans work - they should come on if you are idling in traffic and the temperature gauge starts to rise. When was the last time you had the water pump replaced?