Ok. lately I pretty much top off my reservoir with water then drove 150 miles then when I checked the reservoir its filled with 1/8 of coolant and no water.

Where did the water go? do I have a leak or something?

Also I want to do this for a long time but I don't have a chance to do it.

Is it better to do a radiator flush or the engine block? I have read a few post that the bolt in the engine is very tight. Will the radiator flush will be sufficient enough if I just want to change the coolant in the engine?

Thanks!

 

That's a bit more coolant loss than I would normally expect.
There are two level marks molded into the side of the coolant recovery tank. The coolant should not be filled higher the the upper-most mark.
why?
When the engine heats to operating tempurature, the coolant expands - pushing any additional into the coolant recovery tank.
If the tank is overfilled (as yours sounds to be) the excess fluid is pushed out of the tank past the vent cap.
When the engine cools from operating tempurature , the coolant contracts - sucking the coolant from the recovery tank back into the system.
All this should take place between those two molded marks.
IF after a few days the coolant disappears from the recovery tank, you've most likely got a coolant leak somewhere.

P