Trying to diagnose an alarming knock

[grizzlyjosh]

Hey folks, my '93 has recently developed a loud and scary knock. I have been scouring this and other forums to try to figure out if I'm dealing with a head gasket problem, an injector issue, an oil cooler issue, cavitation or something else I don't even know about but nothing seems to sound exactly what I've got going on. The knock is seemly random at idle but more frequent and louder at higher rpms/under load (I attached a video). I can't really tell if it seems top end or bottom end (maybe louder from the bottom?). Other symptoms were low coolant, though I just topped it up (maybe a gallon) and after driving around for 10 miles no noticable change. It is possible that the cooling system has a small leak that I haven't noticed and is low for that reason. No bubbling or other signs of pressure into radiator when run with the cap off. Heat still works. There is a fairly strong steam out of the oil filler when running, but its been like that since I got it 50k miles ago. It is smoking (greyish) even once warmed up, not much at idle but stronger at higher rpm. The smoke doesn't smell like antifreeze. The oil level has been constant and doesn't look grey on the dipstick but I haven't drained it to see (I'm being cheap, I JUST changed it). As far as driving goes, no noticable loss of power and it starts right up.
I just did an injector test by turning off the key while driving downhill at ~1600 rpm and the knocking persisted with the key off.
I think the next thing I'll do is pull valve covers and see if anything looks wrong under there.
What else can I do? Any thoughts on a possible diagnosis or what to try next?
Well, can't seem to upload the video...
This is a 1993 idi with 220k miles, injectors and pump done at 180k. It has a banks sidewinder on it.

 

[gerlbaum]

Bet your timing is off from worn parts. How old are your injectors and pump? Mine did the same thing, I replaced half the engine (thought I was going to drop a valve, check my posts to see what I replaced chasing this). Knock stayed even with new injectors. Finally got a new pump, went away immediately.

 

[Thewespaul]

Upload the video to YouTube and post the link here. If the knock persists with the ignition off you can rule out the fuel system, but it does sound retarded with the grey smoke issue. I think pulling the valve covers is a good first step. You can also use a temp gun and see if there’s a dramatic temp difference between a certain cylinder

 

[MICHAEL MICHAUD]

Just recently had a very loud knock and I bought a stethoscope from advanced auto for $10. Placed the end of the tube on each injector (you could do glow plug too) to find out which cylinder/s were knocking. Its very easy to tell which ones are healthy, youll see.

Turns out it was #7 and when i opened the injector line the knock went away.

I bought the truck and it started knocking on the way home so naturally I bought all new injectors and a new injector pump and did the glow plugs while everything was out of the way.

 

[IDIBRONCO]

I'm not 100% positive, but at least 97% sure that cavitation doesn't cause a knock. If it does, that's outside my experience. The "steam" coming out of your oil fill is just blowby. It's normal. If you've been driving around any at all with coolant in your oil, it will mix up and you'll be able to tell on the dipstick. I have seen a reman pump that made a knock. this was on a reman engine that I installed. After two more engine changes and a couple of sets of injectors, we finally changed out the pump and there was no more knock. It was sent back to the remanufacturer and all he would say was there was a "bad crush washer" in it. You can also buy a mechanic's stethescope at Harbor Freight for only $3 or$4. I have one and it works just fine. I see that your pump and injectors were "done" about 40,000 miles ago. What was done? Changed out with good, quality components? rebuilt? changed out with cheaper parts store or Ebay pieces? Unless option #1 was used, then I'd guess that at least one of your cheaper parts is failing and now you should use option #1. I'm not trying to badmouth you. I took option #2 the first time and they didn't last. I only had to spend a couple of hundred more to get a Moose Jr. and a set of BB's from Mel (Conestoga Diesel).

 

[grizzlyjosh]

Thanks for the youtube tip. Here is the video:

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. And I made another one of the tailpipe because it seemed to be puffing smoke immediately following a knock:

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[grizzlyjosh]

At around 180k miles (now at 220k) I replaced all the injectors and the pump with a rebuilt pump and injectors (I can't remember if they were new or rebuilt) from an authorized Stanadyne shop.

 

[Thewespaul]

Don’t run the engine anymore.

Look under the covers and do further investigation before you run it again.

Once again, you have the knock persist while the ignition is off, so you can rule out the fuel system.

 

[IDIBRONCO]

I don't know anything either way about one of those shops. It sounds like they should know what they're doing, but who knows? After watching your videos (the first one was enough to tell me) I'd bet money that you have a fuel knock, not a mechanical issue.

 

[IDIBRONCO]

Once again, you have the knock persist while the ignition is off, so you can rule out the fuel system.

I forgot about this point when I made my last post. I probably would have lost that money.

 

[Thewespaul]

I’ll gladly take a beer fund donation jeremy

 

[MICHAEL MICHAUD]

Wow that is one strange knock.

After you verify something isnt obviously wrong mechanically. Use the stethoscope to hunt down the knock. It will take 30 seconds total to listen to each cylinder. Lots of moving parts that could be clicking/knocking. Try narrowing it down.

 

[grizzlyjosh]

I just pulled the valve covers and everything looks normal enough to me, though I'm not sure exactly what to look for. The push rods look straight, the rockers rock when the engine is turned over by hand, there is oil on everything. Is there something else I should be looking for? The only thing that wasn't normal was condensation and grey sludge on the inside of the cover. The oil that was pooled up on the rockers was black and normal looking though.
I'm going to Harbor Freight now to buy a stethoscope.

 

[gerlbaum]

That sure sounds like a misfire to me vs any sort of mechanical knock.

If you could take the truck up to an empty parking lot, get some speed going and while it's in gear shut the truck off. You would be sure to hear a valve noises as it rolled to a stop if there were any.

I have a mechanics stethoscope and when I had a knock I was completely unable to find the culprit with it because of all the other engine noise.

 

[grizzlyjosh]

I just ran it again and listen with the stethoscope and all the injectors sounded about the same. The loudest that I heard the knock was when listening with the probe on the black bladder-looking thing on the turbo (the thing that says 'sidewinder' on it). I can also feel the knock when I have my hand on that. Where else should I listen?
I also ran it this time with the valve covers off and things seem to be normal under there.