Hi I have an Astra Mk5 Automatic and need to replace the water pump. But can anyone advise me how to lock the engine so I can get the crank shaft pully off ??

Robert, August 2009

It's an automatic Steray, not like you to miss that one!!!
According to Haynes, you have to remove one of the torque converter retaining bolts then bolt the drive plate to the transmission housing using a metal bar, spacers and suitable bolts (?!).
I've never done it so can't advise further.
Proper locking tools are available, I'm sure I've seen them on Ebay or automotive tool suppliers.
You can remove the bolt by using a socket and long breaker bar. Fit the socket on the pulley nut, put the end of the breaker on the ground and crank the engine on the starter for a second.
Never crank the engine if the cam belt is loose/removed.
There's not much point doing this though, as you will still need to lock the transmission to torque the nut back up.
Fit a new cambelt/rollers/tensioner kit while you're in there unless you know for sure it has been done recently.

digger, August 2009

put the car into 1st gear,then get a friend to sit inside with there foot wedged on the brake pedal,that should lock it up enough for you to undo the crank bolt & remove the pulley

steray, August 2009