engine knocking SOS
 

All-

I did some searching in the archives and what I found was pretty inconclusive, so I apologise if I'm asking a question thats been beat to death.

My '88 560SEL that I rebuilt started making an unusual noise. It sounds to me like timing is off. I did a top-end rebuild/valve job on the car 1,200 miles ago and while I was there replaced the timing chain, the top rails etc. Now, I know, I know, I should have replaced the timing chain tensioner then, but I didn't. Now my car is making some internal tapping noises which sounds like loud wood-peckers going to work. To me it sounds like the valves and pistons tapping just enough to make noise since it's intermittent. Since I've never had this problem before I'm not sure if my audio diagnosis is correct, so I'm seeking to tap into some experiance.

-FACTS-

First off, I replaced the timing chain tensioner and ran the engine for 1 minute. The knock went away at first and then it started to come back.

The knock is coming from the passenger's/right side of the motor only

During the valve-job, the heads were machined flat.

origional 0-degree woodriff keys used in both cams



When I ordered the new timing chain tensioner, I also ordered a couple of woodruff keys guestimaing at different offsets just in case, besides I needed to make $100 for the free shipping and it was a good excuse :)

Any ideas? Anything else I can provide to help in getting pointed in the right direction? I don't want to take the valve-cover off, but if I have to I have to...


Thanks in advance!


Scott

Update-

Pulled passenger's side valve cover

While working found bolt lodged between exhaust manifold and heat shield.
-Removed loose bolt

Set crankshaft to -0-

Verified passengers camshaft in time-
RESULTS: Timing notch lined up with timing indicator.

Reinstalled valve cover

Restarted engine and let idle for ~1 minute
RESULTS: Rapid knock did not reoccur
Persistance of intermittant single knock ~ 5 second intervals




Is this possibly an injector issue? When I had the injectors out during the rebuild, I noticed that 2 had been replaceded by the P.O.

The injectors are the only thing I can think of now since they're now the only link in the chain which wasn't replaced or refurbed (the tensioner was the other)

If anyone has any ideas what could cause this syptom in a 117 560engine I'd appreciate the help!



Scott

Update #2-

Tried snugging everything down and reattached the loose bolt to its proper place.
RESULTS: Everything was in spec to begin with except loose bolt.
Loose bolt belonged to rear most exhaust port, top bolt. Reinserted and torqued

Ran engine for ~30 seconds until I heard unuaual high-pitched whine and saw copious ammounts of smoke billowing out from the front of the engine. Immidiatly killed motor and investigated
RESULTS: Alternator has seized and belt was spinning around pully, now melted to the pully.

Loosened the alternator and tried to spin by hand. Encountered inital resistance until I tried to spin it backwards and then it "broke" free and spun marginally. Re-tightened alternator and tried re-starting engine.
RESULTS: Alternator spun as intended, then received a series of sucessive knocks then terminated into a high-pitched whine/boarderline squeel & smoke.

My current belief is that my alternator is toast. My next step will be to cut the belt and try running the motor without an alternator for a minute or so to verify.

Wish me luck!



Scott