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Discussion Starter #1
Hello y'all!

So I'm perplexed - when I got my K2500 with 200.000 miles on it, it had several different types of engine knocks, but it also had this kind of "intermittent" harsher knock. I believe the knock to come from the front part of the engine, towards the radiator fan and pulley systems. After reading about engine knocks on 6.5's I ended up thinking it might be the harmonic balancer, the balancer pulley or other pulleys.

I invested in some parts from Leroy and ordered some packages from RockAuto.

I swapped out the harmonic balancer for a Fluiddampr and changed the stock pulley to Leroy's metal billet pulley. The original balancer and balancer pulley seemed in "OK" shape, the some cracks in the rubber but nothing more.

The swap eliminated most of the knocks, but this harsh intermittent one remained. I took a video and uploaded it, I hope some of you 6.5 gurus can have a listen if you've heard a knock like this before.

The knock can be heard at approximately 22 seconds into the video. The knock usually appears every 30 to 40 seconds.


The Coolant Problem

Moving on, I had to take the radiator out and decided it would be a good time to flush the coolant from the system. After disconnecting the lower radiator hose and unplugging the draincock I ended up with approximately 2 gallons of crystal clear, blue coolant. I found this weird, as the previous owner stated that the engine has been pretty much neglected for the past 3 or 4 years.

I swapped out most of the radiator hoses and poured approximately 2 gallons of distilled water back into the surge tank, right above the "FULL" mark. When I started the engine back up I got a "Low Coolant" warning light and what I can only describe as the water pump working on overdrive. When I checked the surge tank again I got the impression that the distilled water I put in just stayed there, as it wasn't even a tint of blue, as if it hadn't mixed with the remaining coolant in the engine.

When I had the radiator out I checked that distilled water moved "freely" through it, so I think I might have clogged thermometers. Could a solution be to take the old thermometers out from the housing, and run the engine without the thermometers? Or should I just put in a set of new ones right away, before I've finished the flush? Could it be something else? I've been afraid to push temperatures after I put in the distilled water because of the Low Coolant warning light.


The Diesel Leak

When I took over the truck, I didn't have any issues with leaks, as far as I know. I checked regularly for leaks during the months I've had it. After starting it up I noticed a diesel leak coming from the diesel lines after the lift pump. I believe the leak is coming from where the lines go up into the engine bay - as the lines immediately after the lift pump are dry. I noticed that the lines seem to have some kind of plastic "screws" or fasteners that weren't connected to anything, so the lines were pretty much freely moving around.

The only parts I've swapped out around this area is the oil cooler lines and oil filter.

I posted a video I took here


I've already got a lot of help from the gurus on this forum in the past, and hope to get some more knowledge from you this time. I'm sorry for the wall of text - I tried to make it as short as possible...

Everything I've swapped on the truck this time
  1. Engine oil to 5W40 super synthetic
  2. Oil filter to FRAM PH5
  3. Oil cooler lines to Leroy's braided steed oil cooler lines
  4. Harmonic balancer to Fluiddampr
  5. Harmonic balancer pulley to Leroy's metal billet pulley
  6. Crankcase O-ring behind the harmonic balancer
  7. Idler pulley
  8. Upper, lower radiator hose, tee to reservoir hose and bypass hose
 

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That noise kind of sounds like the Tensioner pulley bearing could be going bad.

The engine coolant capacity is just a bit over 6.8 Gals. Any time you service the system you will introduce air and it needs to be purged.
add coolant and drive then check, add coolant then drive recheck. There is also a bleed screw on the crossover. keep repeating till air is purged
I would recommend that you not use the FRAM filters. They have a habit of center collapse and it could damage your engine
 
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The fuel line from LP goes from a metal tube into a hose near the FFM.
Check to see if the hose clamp are still good and the hose is still good.
 

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the line after the LP should be metal and the slip in to plastic lined brackets along the frame rail and then another along the driver side of the transmission bolted to belhousing.. If you NEED to get more room behind the FFM to locate the leak you could jack up the tranny slightly, drop driveshaft, remove the rear mount, undo the 4 bolts to crossmember and slide that back out of the way so you can drop the trans a few inches below where it normally sits. It will free up a bit of space if absolutely necessary. My vote is with JMJNet and the leak is near rear of FFM most likely.... feed or return line, or maybe the fuel heater Oring below the FFM itself.

As far as knocking noise idler does sound like a good suggestion as OKDually suggests. It certainly sounds as if the noise is not internal than goodness.... maybe see if the AC clutch is locking up at the same interval and has some bearing issues? Either way you should get that pinpointed before whatever it is explodes! maybe get a mechanics stethascope and poke around a bit. Luckily you say it hapens very often sou hope you can find it soon and check back in. good luck!
 

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Truckr65,

That was a nice organized description.I like it.👍

I definitely would install a new belt tensioner for peace of mind along with new acdelco thermostats.Another thing that comes to mind is have you checked the condition of the vacuum pump?I’d remove the belt and rotate the pump by hand and see if it makes any odd noises but the Ac compressor is another likely culprit for sure.
 

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Discussion Starter #6
Alright fellas, that finally solved the harsh knock!

I tightened the water pump pulley and the power steering pulley, and the knock went away. Feels so good to listen to the engine idle without that knock concerning me every 40 seconds.

But, as is tradition with me and wrenching, new problems arose. I seem to have over-tightened the power steering pulley, and now the serpentine belt "jumps" on top of the edge of the crank pulley, towards the harmonic balancer, and stays there until I take the belt back off again. I reckon about a 1/3 of an inch of the belt is on top of the edge of the crank pulley.

So I figure I have to get myself a new pulley removal tool (broke mine - Murphy's Law), and try to loosen the pulleys again.

Also discovered a new leak that I think is ATF... I'm gonna make a new post about that...
 
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