How can I tell if the timing belt has gone on a Ford Escort 55 diesel van?

Your timing belt has snapped (camshaft not turning). You will almost certainly have damaged valves. Afraid it's a head off job. Cost for this should be around the £250 mark (valves 8 x £11, head gasket set £25, Timing belt kit £60, labour £150) That's from the last one I did. Some garages won't replace all the valves which I personally see as false economy, if your changing 3 or 4 you may as well change them all.

JBM (Scotland)
April 2007