another guy with a tapping 871
11-09-2018, (Subject: another guy with a tapping 871 ) 
Post: #1
another guy with a tapping 871
I figured I should start my own thread. This noise is starting to worry me.

871, 770k miles, 21k hours. @m*m^2 @ 685 k, bypass filter, regular oil changes with gear oil since I got it at 505k. At or around 685k, it got a bearing roll, 6 dimes in the oil pump, new compressor, damper, 2 new injectors, jake springs, overhead has been set twice, a new valve cam, and some other parts.

I suspected my compressor, and at first it only made noise under torque and it seemed worse when it was working. Now, it makes it more under torque, but I can make it make noise at 1000 rpm while stopped, too, even with the compressor unloaded. It does NOT make noise while jaking.

I can say this:
-oil pressure hasn't changed. It's 16-18 while idling, 42-44 while driving depending on RPM.
-engine is not running as smooth as it used to.
-no smoke, no coolant loss, no change in fuel consumption.

I'm 3k miles shy of my next oil change, but I'm considering doing it early and cutting open the filter to check for metal particles. I have a filtermag on the full flow.

It sounds like a case of excessive piston slap to me, but before passing judgement, I figured I have some things to rule out:

- injector check.
- run the engine and see if I can visually see the cause of a noise under the valve cover with it off.
- check the front geartrain for any obvious damage.
- check cam timing.
- check the air compressor for knocking with a stethoscope.
- check the oil filter for metal.
- finally, check the block with the stethoscope for noise from a worn cylinder.

This leaves me with a couple questions:

I can check for a leaking injector, no problem, but what about an over fueling or otherwise failing injector causing a knock?

If everything else checks out, how common is it that a cylinder wears like this? The noise has gotten progressively worse over the last couple of weeks.

I don't drive far, nowadays half of my miles are unloaded, and it hasn't seen mountains or even over 10 lbs of boost in at least 4 months.

I do have a new Cummins damper I was holding onto for my inframe...mine was already replaced, but it's one of those vibratech TVD dampers, not a Cummins. Maybe it's a good idea to throw the OEM on there early even though the TVD is not that old?

Input is appreciated!


User's Signature: 2010 T2000, CM871, 13spd, 930k, tanker yanker
Overhauled @ 927k
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11-09-2018, (Subject: another guy with a tapping 871 ) 
Post: #2
RE: another guy with a tapping 871
My freind had a knock in his. Took it to cummins in Des Moines and the texh heard it as he pulled in. Immediatly said its a timing knock just by hearing it. 1 new timing actuator later and ran smooth and quiet again...
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 Thanks given by: Waterloo
11-09-2018, (Subject: another guy with a tapping 871 ) 
Post: #3
RE: another guy with a tapping 871
It's becoming more obvious it's up front either underneath the front cover or under the front of the valve cover. I can now hear it at a hot idle. Doesnt sound like my last compressor did when I changed it...sounds like something up front is coming loose, like a rocker is loosing its adjustment. Reminds me of what I heard when I flattened out the cam... that would piss me off , all things considered. Maybe a Jake rocker? I'll be finding out in the morning hopefully.


User's Signature: 2010 T2000, CM871, 13spd, 930k, tanker yanker
Overhauled @ 927k
replyreply
11-10-2018, (Subject: another guy with a tapping 871 ) 
Post: #4
RE: another guy with a tapping 871
Pop the rocker cover and check your Jake rocker detent strength.
If they don't "snap" into place firmly, but pop and wobble your Jake check valve springs are weak and the check valve and rocker shafts are worn.

YOU WILL NOT HEAR THIS NOISE WHEN THE JAKES ARE ENGAGED! Why? Because the Jake rockers have Pistons in them that are contracted when not operating, creating a significant gap between the exhaust valve pin and the cam lobes. When they are held in place by the check valves, they are sitting there on the shafts motionless not touching anything. Once engaged, they ride the cam lobe and open and close the exhaust valves at precise times.
When the springs get weak, and/or the check valves and rocker shafts get worn, they start to sag a little, and the exhaust valve starts to hit the Jake rocker, knocking it into the cam because the piston is contracted and it has a significant clearance, it moves hard and fast enough it makes a tapping or knocking sound.

This is very common at or around your mileage.


User's Signature: Why? Why do I always ask "why?" Because I can't learn or help teach others with "'cause I said so..."
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 Thanks given by: hhow55 , Waterloo , trucklogger2 , DosGatos
11-13-2018, (Subject: another guy with a tapping 871 ) 
Post: #5
RE: another guy with a tapping 871
Odd. What I ended up finding is it was the clutch pedal of all things...if I pull up on it or slightly rest my foot on it the noise changes or stops all together.

Some of the noise was the compressor, which went down to normal levels when I'd play around with the pedal.

It seems like it was amplifying the noise from the compressor...however, I also feel some of it too in the pedal. I'm going to lube it up again before I take it out tomorrow and see if it changes. Makes me wonder if the TO {Throw-Out} bearing is simply rattling around while I'm driving around...?

There are a couple of the detents in the shafts that are worn out. Different noise, glad I found it though. More parts to order.


User's Signature: 2010 T2000, CM871, 13spd, 930k, tanker yanker
Overhauled @ 927k
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 Thanks given by: Rawze
11-13-2018, (Subject: another guy with a tapping 871 ) 
Post: #6
RE: another guy with a tapping 871
(11-13-2018 )dhirocz Wrote:  Makes me wonder if the TO bearing is simply rattling around while I'm driving around...?
I have same tapping on my 2250. Sometime it's louder sometime quite. Under high torque and low RPM it's rattling like machine gun. Had transmission dropped for investigation. Haggai guys didn't find anything bad. New clutch, TO bearing, shaft front bearing didn't change anything. The tapping is 100% from clutch area, clutch pedal vibrates even Volvo has hydro cylinders to push TO bearing.
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