Hey guys, hoping I can get a little bit of help with this thing. It is a 1999 C3500HD with the 6.5 Turbo VIN F. Got the truck at 112k, now has 120k

I know my way around a toolbox, but I haven't had any issues with this truck until now. I really don't want to run around buying a billion dollars in parts that I dont need, but I dont know the 6.5 well enough to accomplish this on my own.

The truck starts fine, and runs alright. Touch of smoke on start up (blue/black) but just when it lights, then no smoke. I do not notice any smoke while driving. I have noticed over the past couple days that while on the freeway, the exhaust note would change, and it seemed like it lost some power. If I tipped back into the throttle, it did not always recover immediately. It does not run away, or rev on its own. It always responds with the pedal.

It has a LOT of whistle from the turbo when I get into it. I have been doing some reading, and this does not seem to be the norm. It has a full 3" turbo back exhaust, but the intake is unmodified.

Check engine light came on for the first time yesterday, under light acceleration on a small hill. It did not change how the vehicle was running.

It also has a bunch of codes, but has not given me the check engine light till now. It has only shut off once on me (in the last 8k miles) and told me to service throttle soon.

Codes :
P0122
P0216
P0223
P0236
P1125
P1216
P1217

Things I have done to it so far (since I got it): Flowmaster 2.25 Crossover and 3" downpipe, Aero Exhaust Muffler, dumps out the side right after the cab. All new brakes (previous owner had NEVER done them...), serviced brake fluid, replaced driver side manifold, replaced hydro boost unit (was leaking fluid in weep hole), Replaced lines to Hydroboost at same time, 3 oil changes, 2 fuel filters. I have also run some ATF through the fuel (when I got it...haven't done so in a while) hoping to clear some junk out of the system.

I believe that is all that I have had to do to it so far. It has a service body on it currently, (welder, compressor, diesel tank in bed) a work deck and crane, and of course it is full of tools. Truck rolls normally at 14,200 or therabouts.

This truck gets used every day for work...so I really cant afford to have it out of commision. Any help you guys can throw at me would be greatly appreciated.

 

As for the turbo whistle, you could have a loose air to air boot,clamp,or blown boot.
AS for the other things, i'm not familiar with this motor, wish i could help more,sorry.

 

I appreciate the input regardless, but no damaged boots, and the clamps are all tight. I just had most of the pre turbo intake (it's a very small system) off when I was installing the new down pipe, and I figured I'd take a look at the one coupler I had while I was there.

Found that the vband was loose and the old pipe had a pretty size able leak between it and the turbo. And now I'm pretty sure that the passenger side manifold/turbo gasket probably need to be changed. I'm still hearing an exhaust leak on that side. Which means it'd be a perfect time for an EGT gauge.