Again!? Sudden loud clatter...

[wolf_walker]

I was driving my caddy home from OK to NC a few years ago and about halfway through TN, crawling along in stop and go traffic, there is suddenly a clack clack clack clack clack that sounds about half crank speed and is RPM related.  I limped it to a nearby parking lot and let it sit, fired it up, let it run, and it just sorta quit.  I drove it the rest of the way home and around a bit without further incident, I did eventually remove the head and thought I could see some evidence of something banging around a little in one cylinder.  It idled slightly lower and felt a little "off" somehow otherwise, but no more dramatic symptoms.  I always figured a piece of carbon broke off from somewhere and banged around, maybe tweaking a valve.

Fast forward three years or more, same truck, different motor, been driving it about 6K miles now, and sure enough, slow traffic in town today, clack clack clack clack, the SAME DAMN NOISE.
I checked cam timing, belt tension, etc, etc, visual inspection of cam and lifters, nada, nothing.
WTF is up with this?  Do I need to start pulling heads and cleaning them and the prechambers just on principle when I get a new-to-me VW diesel?  Is carbon buildup that common?

So now, I guess I'll pull the damn head, I was planning a headgasket anyway.

[fatmobile]

Injectors can get a speck of something in them and make a knocking sound.
 I had one sound like a rod was knocking.

[745 turbogreasel]

or a broken spring in the vac pump?

[wolf_walker]

Injectors are new, but it's certainly possible. 

Vac pump is the later rotary style, never was a fan of the early one, even though they are
rebuildable.


Pulled the head last night, it looks to have been replaced at some point, between the valves it's milled
down slightly where they always crack at.  I've seen a photo somewhere showing the same thing, first one I've seen in person like that.  3 valves weep with fluid in the ports, going to pull them all and hand lap them today and check again.  None of the three were more than a weep though so nothing bent I suppose.  I didn't remember these things having dual valve springs and three ring keepers.  Have new seals and hyd lifters also.
One of the lifters looks like it was not rotating well, the lope wear mark on it is very rectangular, the others not so.  They all seemed to move freely and be oily, lifters were little noisy before though.
What a pain to clean the carbon, sheesh.

[wolf_walker]

Done and driving, seems alright so far.  Let it warm up sunday night and parked it, started up rough and white smokey this afternoon, like it wanted the cold start handle out big time, smoothed out pretty quick.  Will see what happens tomorrow.  Weird.

[Baron VonZeppelin]

Back in the old days, when our horse would act up or get weird,  we'd either shoot it - or ride the hell out of it.

I'd ride this one out.

I'm gaining a suspiscion that fresh injectors can make aged InjPumps show their age at a higher degree. My 89 has been doing some finicky things at low speeds sometimes after installing the new remand's. Only a couple more things to try before I put new nozzles in the old injectors and re-install them. Dammdit

[wolf_walker]

I'm pretty sure this thing needs a pump, it's priming and running and all ok, but I don't think the advance curve is for crap. 

Another funny thing is the oil is still clean, lol.  I guess it picks up the black mostly from all the soot I cleaned out of the head.