300 sdl engine knocking noise and turbo woes
 

I recently had my fuel injectors cleaned and re-installed them. Performance has improved greatly as has fuel economy, but ever since, the engine has made a "clicking" or knocking noise while at idle and the frequency of the clicks is proportional to the car's rpm. I have made sure that the injectors were at the appropriate torque value. When idling, you can clearly see the engine vibrating with the same frequency as the clicking noise.

The motor mounts have been replaced a year ago.

This same car used to make the same noise before cleaning the injectors, but back then the noise would subside and become inaudible after about 10 minutes of driving. Now the noise is constant. It was constant after putting the injectors back in, and then removing them and re-installing them to assure they had the proper amount of torque applied.

The cross pipe that goes over the injectors also keeps building up a thin deposit over the top that resembles oil(and has done so for about the past year), but the car itself never seems to consume any oil.

I am suspecting I have a hydraulic lifter issue. The car has about 210,000 miles(odometer broke, so no exact reading is present), and the lifters do wear out.

The trap oxidizer has been replaced before I had acquired the car, but the turbo does not want to dump any boost into the engine. When revving the car in neutral, the turbo can be clearly heard. Could this be a bad boost pressure sensor or a stuck wastegate?

Lifter noise and injector knock are two distinctly different sounds.

Injector knock is a soft sound that lasts a fraction of a second. It's diesel combustion noise that not quite proper.

Lifter noise is a sharp tap, almost instantaneous. It comes and goes...........sometimes reappearing when the engine is very hot...........sometimes when it's stone cold.

Neither event will cause the engine to shake...........which you mentioned is a current symptom. If the combustion in one of the cylinders is very poor, or the compression is low, the issue could be more complicated.

Crack each injection line..........one at a time. Observe the engine each time you do it. It should begin a slow shake and get significantly rougher. But, each cylinder should cause the exact same result. If you find a cylinder that makes little change or no change to the behavior, that's your culprit. Either the injector is NG or there are compression problems in the cylinder for unknown reasons.

The noise more resembles a sharp tap.

I've done this last week, and indeed, each cylinder caused the exact same result.

Just throwin' this out there how do the engine shocks look (my rubber mounts started to pull through) maybe an exhaust leak (tapping /ticking) does it go away after warm up? Belt tensioner shock would be more of a rattle but simple things first and maybe un-related the tapping and shaking

That's a lifter. You can just live with it...........you can run Mobil-1 for 10K and see if that alleviates it..........or you can change the lifters but it's a bit of work and not all that cheap.

An exhaust leak is also a suspected culprit. I'll have to check the engine shocks; what problems should I look for with regard to them?

I've been running Mobil-1 full synthetic 15W-50 for about 6 months. The noise has not gone away in the least.

Will the lifters going un-fixed eventually cause problems with this engine? I'm intent on keeping this car for a long time, possibly decades, given the longevity of these engines. The body will probably give way to rust long before the engine has terminal problems(in which case I will obtain a 300 SL gullwing replica to put the engine and transmission into).

I don't think I'd tolerate a single lifter that was making noise on a constant basis. Besides the annoyance factor, the constant hit between the lifter and the camshaft cannot be good for durability over thousands of miles.

But, on the '86, it's intermittent..........maybe 10% of the time. That's quite tolerable considering the alternative.

I don't think that's a diesel-rated oil. Probably you want the 5-40 Turbo Diesel and Truck oil.

Mobil 1 15W-50 meets or exceeds the following industry specifications:
API SM,SL,SJ,EC,CF

There are six diesel engine service designations which are current: CJ-4, CI-4, CH-4, CG-4, CF-2, and CF.

I beg to differ, but I use the 5W 40 turbo diesel truck oil.

I'm trying to track down a noise as well... does your noise sound like this? http://www.youtube.com/watch?v=3m974_BIH3o