I have a 1993 chevy 3500 with a 6.5.When the engine is idling,I can hear chatter which seems to be coming from behind the cover directly behind the harmonic balancer.It's almost undetectable when I'm driving.Also,I'm not sure if it's related,but when I push the clutch in to shift while crusing,the engine sometimes dies or nearly dies.My idle speed is about 900 rpm.This seems to happen more when the engine is not fully warmed up.Any advice would be appreciated. Thanks Nick

I'm no expert but it may be your balancer itself is on the way out, look for protruding or missing rubber, see if the bolts on the balancer are still centered or if they're up against the 3 spokes, pull off your belt and wiggle the balancer to see if its loose. If the balancer is loose change it ASAP, don't drive it or you risk a broken crank, cracked block, etc. Someone with more expertise please chime in here.

Check out this post for more info.

http://dieselplace.com/forum/showthread.php?t=18013

The engine sometimes dies or nearly dies. My idle speed is about 900 rpm.
The injection pump is the only thing that controls engine speed, if your idle has increased to 900, and still stalls/almost stalls, sounds like you might need an injection pump. Metering valve could be binding keeping the governor from reacting quickly enough to maintain idle speed. Check supply pressure, check for air bubbles in the fuel, check to see if cold fast idle solenoid is interfering with throttle lever L.I. position and try to adjust L.I. lever to idle at 700RPM, and try a lubricity improving fuel additive. How many miles are on the Injection pump anyway?

I'm not sure,I bought the truck about 9 months ago.The engine was replaced once,but I'm not sure about the pump.My idle has always been about 900 - at least thats what the tach says.The only difference I have noticed is when I let off the gas to shift,the engine drops below the 900,and almost stalls before I let the clutch out again.It seems to do this more when the engine is not fully warmed up.This is a new development.As for the noises I hear,that has remained a constant as far as I can recall.Almost reminds me of a timing chain slop sound.It's easy to hear when you stand away from the truck,and almost impossible to hear when looking down from the top of the engine.since I have never had one of these engines apart,I'm not even sure whats behind the front cover.I'm really glad to have found you guys. Thanks again

Nick

If the timing chain were worn/streched badly enough to make as much noise as you describe, the injection pump would not be able to be staticly timed advanced enough to take up the slack, and cam timing would be so slow you would have smoke and low power.

Hey,thanks for the advice.I added some fuel treatment and the problem stopped after about 20 minutes of driving.I just took an 800 mile trip last weekend.Mabye I got some crappy fuel.As for the noise,I'm going to pull off the belt tommorow and see how things sound.I'm going to take a 3000 mile road trip in 2 weeks.Thats why I'm concerned.A friend of mine has a shop and he listened to it.He didn't seem to think much of it.He told me his was making some noise as well.Told me I should ask some 6.5 owners if they hear any similar noises in the same area.

Read 'Clatter from engine' post for some scary stuff..........
Also check alt, vac pump, p\s pump bearings
Check idler pulleys
Check idler tensioner pivots

This morning I took off the belt and I still had the noise.I removed the crank pulley,and still,the noise is there.The balancer appears fine-so does the pulley.being I never saw the guts of this thing I have a question.Does the gear and chain setup have a tension adjuster on it?Is the crank gear similar to a small block setup in that it is held in place by a woodruf key?How is the gear and chain oiled?Is it possible the oil hole could be clogged?My oil pressure is good.The noise sounds like a chain sound to me.Thanks for all the help.

Nick

Similar to small block but heavier duty than big block - dual-row semi-roller chain and sprockets.
Probably would not hear timing chain slap thru cast aluminum cover, unless chain was hitting cover.

You did not mention mileage before\after engine R&R, but the pump driven gear could be loose, same for drive gear or cam key sheared.
Chainset could be loose - BIG OR, here - key slot in harmonic balancer could be damaged, resulted from loose crank bolt.

All these things have happened and been reported - might be a good time to pull balancer and timing cover for a mechanical inspection

Any or all of which could also explain the idle problems - timing is erratic.

Almost fergot - if you're brave enough to crank it one more time, open oil filler tube and listen.
It's gonna sound like a chainsaw on an iron pipe, even with new chainset, but may help to correlate the sound you're hearing.

Good luck, dude..........

...open oil filler tube and listen. It's gonna sound like a chainsaw on an iron pipe, even with new chainset...
I just have to say, having replaced a timing set on mine, while my new set is certainly not silent, it is barely noticeable anymore, if it didn't make more noise when it was worn out, how would anyone be able to hear the difference then?

Good question -

Even a third-degree, Golden Ear, high-end music afficionado cannot hear the chain-set noises thru the cast-aluminum timing cover.
Removing the oil-filler cap while this engine is running would send anyone not familiar with this engine scrambling for his tools.

NC is hearing a noise suspected of being inside timing cover - if so, he will hear it clearly thru open oil-filler tube.

Must excercise some CAUTION while listening at close range - the fan-blades, spinning at engine rpm, are near, exposed, and dangerous to fingers, elbows, shop rags, etc.

And, the occasional Golden Ear..........;)

Looking, touching, and listening make up 50% of any skilled trouble-shooter's toolkit.
Unfortunately, those 'tools' are also the most difficult to teach to the new guys coming out of the tech schools.

Ahhh.... Zen and the art of diesl mechanics. Your ways are spreading my friend.

I guess you don't see what I"m saying, I agree, when the chain wears out, it makes a lot of racket, but what you said was that even a new set will sound like a chainsaw on metal pipe, I'm just saying that the sound is definitely increased when its worn out.

Any one unfamiliar with this engine, listening at the open oil-filler tube, will imagine a tear-down is imminent, old chain-set OR new chain-set.
These "normal" growling\grinding noises are not detectable thru the cast cover, being masked by Diesel rattle normal to indirect injection.

Any noise heard thru that casting will make itself known thru the open tube, over and above what is considered as normal.

I suspect all of the above, with emphasis on harmonic balancer keyway damage, not being there to look, touch and listen, but noting his insistence that the noise is in vicinity of hb......

Could also be timing is so far retarded, Diesel rattle is low and not masking other noises.......