Kinda hard to say Rob. You might be able to warm up the engine, then(VERY CARFULLY!!) take off the radiator cap and have someone rev the engine while you watch the coolant. If you see bubbles... that's not good. If you see MORE bubbles the more you rev it....that's worse. Not saying that's the only way, or best way to check it, but it has worked for me several times.

<EDIT>I suppose you could also pressurize the cylinders with compressed air some way and watch for bubbles(like above) without starting/running the engine. I have never done it that way, but it MIGHT work. The air pressure used would need to be pretty high though. Engine still needs to be wamed up too. Small cracks seem to get bigger(and leak more) as an engine warms up.

Here's hoping you don't see bubbles. <img src="/forums/images/graemlins/cheers.gif" alt="" />