I am having some diagnostic trouble with my 1998 Suburban 50k miles. Last year it lost an oil line & all oil, the engine still ran. Unfortunely I got the run around from two mechanics and spent a ton of money getting bad diagnostic & repair advice before finally getting it repaired: new crankshaft (old grooved by failed rod bearing), piston rod & rings for #8 piston, all new bearings, new harmonic balancer, pulley, tensioner, new erg, & rebuilt heads (part of the misdiagnosis). Turbo taken to Majestic Turbo in Dallas, checked out ok. The engine starts fine, runs strong, stays cool, has good power, turbo whine under acceleration, no large amount of black smoke. The problem now is that there is much more "clatter" than it had previously, there is a "poping" or "puffing" sound (not a clatter or metalic sound)coming from the upper right side, & a strong vibration is felt all the time, and when at idle there is cycle to it, one second it vibrates then it vibrates more and repeats. I am not a mechanic, just a tinkerer, and have no clue how to diagnoss the problems, but would like a mechanic I can trust & talk to, unlike at the dealer where you only get to talk to the "service advisor" who knows less than I do about a diesel. ANY help, advice, referalls, or information will be greatly appreciated. Thanks Chris

Texas Diesel Performance (http://www.texasdieselpower.com/gmc.htm)
Try this place.They are located in weatherford.They do work on 6.5's,have performance parts in stock,and know most of the quirks regarding them..

a popping or puffing sounds like the noises mine made when it had a cracked piston. I pulled a valvecover and started it up and watched. I noticed black smoke being shot into the crankcase everytime the #6 cylinder's compression cycle hit. A strong vibration at idle is usually a strong indication of cylinder imbalance from compression leak or stuck /sticking lifters.

Thanks for the replies. Could cracked piston could be causing the puffing noise and the imbalance? What would cause the imbalance if not the piston? This doesn't sound like an Inj. Pump issue, especially with all the extra "nailing" & clatter? I am almost afraid to ask, but is the only solution a piston or worse? I have experienced higher oil usage than normal, is this a symptom as well of a cracked piston? Could it be the rings were not installed properly or have not seated properly? Will driving it in this condition hurt the engine or cause high oil use etc? Thx Chris

My truck had a strong vibration when the rubber in my accesorry drive pulley went out. Easy To check with engine off grab the accessorry belt and try to move it, if you see the pulley on the crank shift back and fourth about an inch it's bad. $116 from gmpartsdirect.com. E-Z to change remove the belt, pulley is held on by 4 (15mm) bolts.

Yep, in an effort to avoid problems I had a new one installed when the engine was put back together. This vibration is not a "shaking" kind of vibration, its more like a "buzzing" kind of vibration, at least that how it feels through the pedals and steering wheel, like metal is touching metal somewhere. If you placed a large & unsecured electric motor on a table and turned it on, might make this fibration I feel, its the only way I know how to describe it. Not sure an imbalance in a cylinder would cause this or not.

check you air conditioning compressor, alternator and vacuum pump i've had similiar symptons as you are describing when they were on the way out. Run the truck with the air conditioning on max and watch the clutch on the front of the air conditioning pump as it engauges and disengauges, see if the sound corresponds to the clutch movement, then run it without air on and the heater controls set to the floor only, see if the sound is still there. Remove your belt and turn the pulleys by hand, my air conditioning compressor did exactly what you describe yet ran for another 6 months before i had to replace it. This won't account for high oil consumption but its worth a check.
One other thought would be to check that nothing is rubbing on the firewall behind the engine and the exhaust is not rubbing anywhere either.

The a/c compressor is not on, and when it is, it has a different vibration. This vibration seems to be coming from the Injector or the lines. When I touch the Inj lines its the same sort of vibration I am feeling when inside, only it seems to be magnified. Also, this vibration is getting worse, and sometimes it almost feels like it is missing. I have tried using injector cleaners but no difference. Also, I forgot to mention that the injector line holders at the valve covers are missing, one of the previous mechanics lost them, among a host of other items lost, and it wasnt until the mechanic who put it all back together were they noticed missing. I can't imagine this would cause this strong vibration. I did try to order the new holder (for lack of correct term) from the dealer but they couldnt figure out what a part number would be for them.

Maybe its just a bad injector tip, without the clips to hold the lines in place you may be able to use a stethascope on each line to listen for a difference in noise, no stethascope then use a long screw driver to the line and your ear and listen for a difference in line noises or even better listen right at the injector if you can.

My truck had a strong vibration when the rubber in my accesorry drive pulley went out. Easy To check with engine off grab the accessorry belt and try to move it, if you see the pulley on the crank shift back and fourth about an inch it's bad. $116 from gmpartsdirect.com. E-Z to change remove the belt, pulley is held on by 4 (15mm) bolts.
Autozone and O'Rielly's carries this part also.I paid $53.00 for mine last month when i had to replace it.My truck also had a slight vibration untill i changed that dampener out....Takes 5min and it has to be done sooner or later...

Did you try removing the belt to see if the sound/vibration went away?

The dampener, tensioner, harmonic balancer, & belt are ALL recently replaced. I have not taken the belt off to see if the vibration goes away as the vibration is what had me change all of those anyway. I will try to do that tomorrow and see if there is a difference. I am not much of a mechanic, and I am way over my head with this Suburban. Sadly, every time I drive it now, I get a pit in my stomach, wondering what each new noise is, and fearing it will leave me stranded on my way to work and/or cost me another $6000 grand to repair, cash that I just don't have right now. I just keep my fingers, eyes & toes crossed <grin><GRIN><GRIN>

DSG,
Check for loose brackets/clamps, fuel line touching the engine, I thought I was having some serious issues, turned out to be a loose heat shield on my turbo at accentuated the "normal" knocking coming from my engine. How many miles on your injectors, if high miles migt be a good time to pull them and have tested, my local injection shop does that for $8/ injector, also if you can park some place where a little fuel does not matter, 1 by 1 crack injector lines and see if you can isolate which cylinder the noise is associated with.

Does pulling the injectors require any special skill or tools? What kind of place will test them. There is heavy duty diesel mechanic shop close will they be able to test them?

Today I started up my 1983 6.2 Suburban, and it soooooo much smoother and quieter then my 6.5. I was going to drive it, but my luck (or lack there of), a freeze plug broke on the right side, so gonna have to get that fixed now.

You will need a deep 30mm socket to unscrew the injectors, a regular wrench and socket set will take care of the rest.
Depends on what kind of work they do at this 'Heavy Duty Diesel Mechanic Shop' as to whether they will have a pop tester or not. If they rebuild pumps/injectors for sure they will, if they mostly deal with engines or tractor/trailers then they probably won't have one.

I guess I will have to find one in Dallas. Any recommendations on that?

Also, I was touching things in the engine compartment, and a strong vibration is coming from the Turbo, not sure if the turbo is making the vibration, but is definitely has the "buzzy" sorta of feel that I am feeling on the pedals and steering wheel. Do turbo's have this sort of vibration or could something be causing it to vibrate and since its held out on a bracket the vibration gets magnified?

have you checked the down pipe/crossover, sounds like they might have just left something loose on the turbo side. There's a tin heat shield between the turbo and the injectors that can rattle if left unsecured also.

I know a real good diesel injection place that can help you....but they're in Abilene, don't know if thats too far, about 2-2˝hrs depending on where you are, but they're the best in the state.

Thats something I need to check. But even when I am going 65 mph and the rpms are at 2000, the clatter sounds like I am going 100 mph in 3rd gear.

Thanks 95-6.5, When I went to Autozone looking for my pulley the "Moor-on" behind the counter insisted I was looking for the harmonic balancer (which they don't carry) and sent me on my way. Then I found gmpartsdirect from this forum which I was glad to find, since the dealer rips you $270 for this part. You've saved me future $$$, the first one did last 185K miles, hopefully way future.