don't forget Ff on the slab to the right.
Also for the slab, you have add its mass with the mass of the block:
(M+m)g for the equillbrium between the slab and the horizontal surface. However since the horizontal surface is frictionless, you won't have to worry with this value in your...
disregard my last reply. I was just reading about this engine, and you probably want the P/V diagram, check out factbug.org
It says this engine operates around an otto cycle. I'm certain you can google a graphic of an otto cycle pv diagram. Then, perhaps modify it for your purposes?
daveb is right. however, I'd like to say for practical purposes, should you find yourself having radiator issues, the best thing to do is wait for the engine to completely cool and then just add the water. Theres even less risk of cracking the block that way. As far as the other two, perhaps...