Help! This one is actually on a coach engine, but it has us all head banging, so any suggestions gratfully recived. Symptoms Last night coach overheated, no loss of power and got back to yard. Today, check of engine oil dipstick showed it over full, cooling system full of yellow fudge and coolant black. Drain and flush cooling system till water came out clean Check dipstick showing over full . Sump capacity 35 litres. Take out sump plug, about ten litres at most comes out. Dipstick still showing over half full? At one stage the engine was run over, nothing out the sump, engine running fine. So what the flying blue blazes is going on?