Thanks for the input. I just started it up cold. sounded fine for 5 sec, then clacking began. I used a scredriver crammed to my ear to check listen to each cylinder by the injector, and to each IP injector. The #2 cylinder sounds like the one making the noise. After 1 minute smoke was pouring out of the tailpipe and wafting down the street.

Ref, the top radiator hose was-and-is soft squeezable, no pressure in the cooling system, and the coolant tank is still clear. I have not adjusted the ALDA or messed with the IP (though I have replaced "o" rings on a previous 124TD)

Sixto, performance may be a bit off, but I haven't really pushed it since this pretty sudden onset of smoking, and then smoking and clacking (I don't remember hearing the clacking right away, the radio was on). This TD used to do 0-60 in 10.5-11 secs.

So to look into the cylinder head pre-chamber, is the process to remove both injector racks , or just the one with the 3 that feed the #2 cyl? Do I remove them from both the IP and the cylinder injector? And after looking for the bb, should I swap another of thsee 3 injectors to #2 and then reassemble the fuel feed lines to test the injector itself in the new cylinder, and then listen to #2 to hear if it is still making noise? Is that the process? PS what is the heat shield?