u wana check diesel engine ... so ... cool it down and start ... it will give pukh pukh sounds ... then when it will heat it will lessen the sound or remove that pipe that goes f4rom engine to airfilter if there wud be engine oil then u can know tht its bad engine ... it will make pukh pukh sound ....
dont know abt petrol engine...
My advise take a mechanic with u and let him check it ... thats best option ...