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93 C3500, Crew, LB, Duals, F code with 141 Block. Replaced 90% under the hood this year.
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Discussion Starter #1
Hi all. 18 months ago we set out to find what was causing the typical Tap Tap Tap noise emanating from the engine. I've read hundreds of threads and gone through FAQs etc. No significant blow-by.

This is what has been replaced with a new replacement part:

Oil Pan
Oil Pump
Rod bearings (mic'd each one and they were still std. I was told this engine only had about 75k on it)
Rod cap bolts
Front engine cover
timing / Injector pump gears
Front Eng Pulley
Harmonic balancer
Injector Pump
Injector lines
Injectors
Glow plugs
Glow plug controller
Glow plug harness
Cam
Lifters
Push Rods
Rockers
Nylon retainers
OP sensor
Fuel Manager
Fuel Pump
Water Pump
Water Pump Pulley
Alternator
PS Pump
All A/C components
Complete Turbo Assembly
Exhaust manifolds
Radiator
Trans Cooler
Transmission (4L80E)
Flex Plate and bolts
Torque convertor and bolts
Belt tensioner
Belt
All hoses
Fan Clutch
Batteries
Batt cables

Good news - it runs great. Bad news - That tapping did not change at all. It is at CAM rpm, 800 RPM engine and this tap is 400 Taps per minute. It does get just a bit softer after full warmup, but is is always there. Drives me crazy... What have I not changed that that operates at Cam speed? I don't mind replacing more, but I have run out of ideas.

Thank You!

Jim P

93 C3500, 6.5 TD, Crew cab, 8' bed, 2wd, 4L80E, Dually, 141 block
 

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Add a can of Seafoam to your FFM and let the engine idle and see if the noise changes
 

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It's easier to write down what you haven't replaced yet, since you're this far.
 

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Premium Member
93 C3500, Crew, LB, Duals, F code with 141 Block. Replaced 90% under the hood this year.
Joined
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41 Posts
Discussion Starter #4
Add a can of Seafoam to your FFM and let the engine idle and see if the noise changes
I'll do that tomorrow. I did put injector cleaner / lube in the FFM and tank a couple hundred miles ago with no change. seafoam great idea!
 

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Premium Member
93 C3500, Crew, LB, Duals, F code with 141 Block. Replaced 90% under the hood this year.
Joined
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41 Posts
Discussion Starter #5
It's easier to write down what you haven't replaced yet, since you're this far.
That's where I run into a dead-end. I can't think of anything else.
 
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Premium Member
93 C3500, Crew, LB, Duals, F code with 141 Block. Replaced 90% under the hood this year.
Joined
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41 Posts
Discussion Starter #6
I'll do that tomorrow. I did put injector cleaner / lube in the FFM and tank a couple hundred miles ago with no change. seafoam great idea!
How much Seafoam OKDually? 25%, etc.?
 

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Is it normal injector chatter? Also These engines make a lot of noise when cold, its normal. Every 6.2 or 6.5 I have heard. Sound like the end of the world on a cold start. Went away as engine warmed. Never worried about it.
 

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I havent had time to start isolating some of my mystery sounds (one is a soft metallic ping/ringing and the other sounds like an exhaust leak near the turbo area...)

Anyways, one thing that was not mentioned on your list of things to try was running the motor without the belt. That would eliminate anything belt driven. Looks like only belt driven item left on the replace list is the vacuum pump.

Quick and free to try! Good luck! Also uploading a recording MIGHT help someone recognize it but this sort of thing can be hard over the computer.
 
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Premium Member
93 C3500, Crew, LB, Duals, F code with 141 Block. Replaced 90% under the hood this year.
Joined
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41 Posts
Discussion Starter #10
The one thing I know I did not replace is the RPM / Oil Pump driver. It is driven off CAM. Did not replace it since it worked fine and it's about a $300 item.
 

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Premium Member
93 C3500, Crew, LB, Duals, F code with 141 Block. Replaced 90% under the hood this year.
Joined
·
41 Posts
Discussion Starter #11
I havent had time to start isolating some of my mystery sounds (one is a soft metallic ping/ringing and the other sounds like an exhaust leak near the turbo area...)

Anyways, one thing that was not mentioned on your list of things to try was running the motor without the belt. That would eliminate anything belt driven. Looks like only belt driven item left on the replace list is the vacuum pump.

Quick and free to try! Good luck! Also uploading a recording MIGHT help someone recognize it but this sort of thing can be hard over the computer.
I will add a recording tomorrow. Also, there is no air pump on this.
 

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1994 K2500 Suburban 6.5 turbo.
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a recording would be great. Diesel engines do run a little on the loud side especially when cold. When it gets very cold in the NW and I start my sixfive up I have heard what sounds like the engine would blow a piston buts all is good. And when I say very cold in the NW it might be 25F so not real cold. Also my 6.5 is much quieter once it warns up.
 

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👻💀☠👽👻💀
🎃The tapping noise..... it's getting louder! Getting CLOSER!!! OMG, it is not coming FROM the engine! OH MY GOD, IT IS THE ENGINE!!!! AAAAARRRRGGGGGHHHH 🎃
hahah sorrry still in halloween mode.

I will add a recording tomorrow. Also, there is no air pump on this.
There is soooo much oil that would be enveloping the oil pump driver when running it would be hard to imagine a tapping noise but anythings possible. I am sure you have a mechanics stethoscope by now?
 

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93 C3500, Crew, LB, Duals, F code with 141 Block. Replaced 90% under the hood this year.
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41 Posts
Discussion Starter #14
Will get the recording tomorrow, work rules on some days. And yes, I have a mech stethoscope. Anywhere on the engine it heatrs that loud, singular tap tap tap. Take off the intake plenum and that sound is like a bullhorn. ??????? I'll get the recording and go get some seafoam.
 

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93 C3500, Crew, LB, Duals, F code with 141 Block. Replaced 90% under the hood this year.
Joined
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41 Posts
Discussion Starter #15
Here is a link to the noise. The engine had been running maybe 1 minue, so this is cold. Once fully warmed it is better, but still there.
And I forgot a few things that have also been replaced:
All Valves, keepers, seals
Starter

 

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Here is a link to the noise. The engine had been running maybe 1 minue, so this is cold. Once fully warmed it is better, but still there.
And I forgot a few things that have also been replaced:
All Valves, keepers, seals
Starter

That noise almost sounds like a vacuum pump on its way out.
Try removing the Serp belt and run the engine briefly to see if the noise disappears
 

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Premium Member
93 C3500, Crew, LB, Duals, F code with 141 Block. Replaced 90% under the hood this year.
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41 Posts
Discussion Starter #17
This one has no pump and no egr from factory. I'll start it without belt just to see.

Thanks!
 

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My 93 has been making the same noise. It runs great but taps exactly like yours does.
 

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93 C3500, Crew, LB, Duals, F code with 141 Block. Replaced 90% under the hood this year.
Joined
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41 Posts
Discussion Starter #19
Same noisde without belt. Literally everything touching the belt is new. A/C compressor, PS pump and pulley, Water Pump and pulley, Crank pulley, HB, Tensioner, Alternator. :unsure:
 

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That's a bit more than a tap....

I would put a large breaker bar on the crank bolt and attempt to rock the motor both ways and see if you can feel any slop or hear a bump.... Like a rod bearing being loose kind of slop...

If nothing their dig into the valve covers and see if anything in the valve train is loose or broken...
 
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