Tapping Noise
 

I have a 300TD that I've owned for a couple/few years. The whole time I've run it, it has had a tapping noise that is quite noticeable when cold that sounds like a valve. It sounds just like a car with hydraulic lifters when one of the lifters doesn't work. Tap, tap, tap. The noise is very intermittent, tho. Usually with a bit of a drive it can go away entirely or come and go. All valves have been adjusted twice in the time I've owned it. All the injectors have been rebuilt once with new nozzles and checked another time. I'm thinking my next step should be to run it with all the accessory belts off to see if the noise goes away. Any other thoughts?

Could be the vacuum pump. Might try the screwdriver to the ear trick on the vac pump and see if you can isolate the noise.

Check the bolts that hold the AC compressor to the mounting plate. The rubber grommets get dried up, leaving the compressor loose.

Rubber grommets? Have a picture?

It's not every day that you encounter a belt-driven component mounted with rubber.

The MBs with the York Compressors have metal bushings with large rubber grommets around them holding the compressor to the bracket.

i also have a ticking noise that sounds exactly like a lifter[na 606], but when you try to isolate it with the stethescope you always windup at the injectors.flusteratting! i just finished changing out a bunch of lifters with no change, also swapped around some injectors, still no change. can injectors cause this noise? hadn't considered the vacuum pump. again, can an injector cause this?

thanks, hunt

I have heard injectors make that tapping noise, but I do not believe that is my problem. I should also mention that I loosened each injector in turn. There was a similar drop in rpm with each and the tapping did not go away. I will check out the vacuum pump and try to isolate the noise further. The A/C compressor is mounted solidly. I may pull all the accessory belts