engine tapping,

hello there, my mates got a 200tdi 90 and it has a really anoying tappy noise, the tappets have been done and it has made no difference, also we have chaged the manifold gasket and swapped the manifold, checked all of the exaust, checked the head gasket hasent gone, but it continues to 'tap' if anyone knows what this could possibly be i would appreciate some pointers because its getting unbelevably anoying, thanks, Bryn

May be an injector ! Crack off the injector feed pipes one at a time with engine running! If it's an injector the noise should go away as you undo the pipe to it !!if this is the case replace the injector and see if it's cured!!! You say you checked the head gasket !! How did you check it?? Compression test is best!! All cylinders should be within a few psi of each other ! The gasket is prone to failing to atmosphere at the back of the head !! Nearest to the bulkhead sounds like a strange tapping noise too!!!! You can usualy feel the hot gasses on your fingers if you feel around with the engine running !!! Does the noise get louder or does it disappear when revving engine a bit?? Both of these things may get quieter when revving up !!!!! Good luck

I have tryed putting my hand behiind the head nearest the bulkhead as u say and its fine, the 90 has pleanty of power pulls well and dosent sound like its missing or got an injector down. The tap dowes get louder the more you rev it up. when i say a tap i mean it is a 'fut fut fut fut' sort of noise. thanks