That sounds like something in your drivetrain is dragging, perhaps a caliper or the emergency brake? (Just throwing that out there.)

 

Lately my 6.5 is blowing major black smoke in second and third gear before the engine gets up to normal temp. Once up to normal temp I get the occasional puff of black smoke while changing gears. There seems to be plenty of power and it idles fine. Also when cruise control is set around 65 to 70 I get a feeling like something is tugging on the truck, off and on. It's the original turbo for 94 with 245,000 miles. I change ou the air filter but did not seem to help. Any thoughts?:confuzeld

Black smoke means not enough air. Sounds like it's time to do a systems check.

Air Filter (Change if dirty)
Wastegate Solenoid (can get sticky and not allow wastegate to hold boost)
Vaccuum lines from solenoid, vaccuum pump, and wastegate actuator. (Check for cracks)
Wastegate actuator (Diaphram can get warn out and leak)
Vaccuum pump (Common to go bad and not produce enough vaccuum)

All these can contribute to the wastegate not holding boost.

Also check the turbo for excessive shaft play or damaged blades.

 

Hook up a boost gauge and report back.

 

Check for DTC's.

FWIW, heres DTC 78 Diagnostic Chart

 

The vacuum system gave up earlier than the turbo and a lot cheaper.

Follow the diagnostic from HC above before condemning the turbo.

 

Sorry haven't got back sooner. Been at a conference all week. I have Heath Turbo master so no vacuum pump. I do have a boost gauge which seems to read normal values except when cruising 60-70mph. Not sure if it drops due to turbo or whatever is making truck lag. I put a new filter on before posting just to make sure. Didn't help. I haven't heard any unusual noise coming from brakes, parking brake or drivetrain. The lag only seems obvious at cruising speeds especially while cruise control engaged. It does see to have improved a bit since the 400 mile road trip this week. Wondering if I had some low quality fuel. Up till the road trip, its mostly been short around town driving.

 

Are you saying that there is little to no boost at highway speeds? That's how it should be. You only want a few PSI when not under a load.

 

Do you have a boost gauge?

I would be more inclined to think it was in issue with the waste-gate not sealing, that usually happens before a turbo wears out.
They actually rarely wear out unless the wheels get damaged by ingesting something or touching the housing.
Another common problem is the crossover not sealing, so the turbo doesn't get all the exhaust gas it should to drive it. Any abnormal exhaust noise?

edit, you answered as I typed... lol

Try some PowerService and 2 stroke oil in the fuel. See if that wakes it up. It may be a sign of injectors or IP not performing up to par.

 

when the LAG occurs, what is going on? climbing a hill? wind?

 

What boost levels are you seeing?

 

Boost usually climbs to about 8 while shifting 2nd and 3rd unless I push harder. Cruising about 65mph it sets about 3. If I punch it the boost will jump to 12-14. I haven't tried since getting home but while on interstate with cruise control set it would lag and drop out of cruise control. No hills, no wind just flat interstate. I plan to check for manifold leaks tomorrow and loose crossover pipe. I have noticed exhaust will get this deep vibrate occasionally while sitting at a light. I'm wondering if the 94 exhaust manifolds are not setting well against this newer engine with no exhaust manifold gaskets. Also, should there be a gasket between turbo and exhaust manifold?

 

NO gaskets are used on the exhaust manifolds, not between the cylinder head(s) to exhaust manifold(s) or exhaust manifold to turbocharger.

Im trying to think of the condition when the boost pressure suddenly spikes/backups into the compressor housing, say when your changing gears or suddenly decelerating..
It can cause significant damage to the compressor wheel and thrust bearing..

 

Check for oil inside the intake

Turbos will leak oil past the seal when the seal ring wears and the shaft bushing (bearings) get loose from wear.. Then it will throw the A/F ratio out - and the turbo will not spin smoothly either as it leaks and sprays oil. Depending on which cylinder gets the most oil flow - you will feel it as a misfire.

I had this happen on a Toyota Turbo Diesel I owned. It would run great for a while around town - and OK on the highway - if I kept it under 55-60 mph - but above that the seals would just leak oil right into the air stream - there would be a cloud of black smoke - and it would loose all power until I pulled over and let it idle to cool the turbo.

You said it has 245,000 miles on it. My 6.5 has the same mileage age and it is leaking oil into the manifold - but since it heads down into the intercooler first - I get a more dispersed spray of the oil and the engine treats it like only dispersed fuel. I will rebuild it soon - I really do not like oil in the intercooler - though it really keeps moving as an airborne spray sort of.

Since I have a center mount turbo in a van - the stock intake cross over had most of the oil going to the passenger side of the engine - and it ran like crap with ignition delay noise on that side of the engine until I put on the intercooler.

So yes - I would bet it is probably time for a rebuild on the turbo - with that kind of mileage and if you see oil in the manifold that will confirm it.

You want to do it before the bushing/bearings get so bad the turbine or compressor wheels hit the housing - then you have to buy expensive parts or a new turbo.

 

Your turbo boost with actually rise when you feel the lag, IF something was hanging up on your vehicle. Because as drag increases, turbo boost increases. But like savvy65 said, I too think it sounds like your turbo is due for a rebuild. I'm about to do mine this week.

 

Your boost numbers look about normal, till you get to the lag part.

It could be something that plugs up as you get it hot. We've seen the inner cross over collapsing intermittently. Wonder if the soot trap could be causing issues.

 

Air filter condition? Have you checked the turbo for play?

 

Live in Florida and rained all day today and tomorrow too, so I haven't been able to check out the suggestions. Will try and look for oil in intake if the rain slacks and also check for loose exhaust. The cross over is heath 2 1/2 ss. Not sure what the soot trap is. Need any special tools to rebuild turbo? When I installed the Ted's engine back in March there was oil in the intake so it will be interesting to see if any or how much now.

 

FWIW..


Crankcase Ventilation System

General Description
The crankcase ventilation system used on [GM's 6.5TD] diesel engines is designed to maintain a slightly negative (vacuum) crankcase pressure across the [entire] speed range. The system consist of a Crankcase Depression Regulator (CDR) valve, located on the right valve cover and the attaching vent hose/pipes to the engine [air] inlet system. The CDR valve is only used to regulate crankcase pressure between 0" and -4" water depression over the engine speed range. The CDR valve is NOT an oil separator or a crankcase effluent flow regulator. Hence, the CDR valve DOES NOT prevent oil droplets/mist [vapors] from entering the intake system, nor does it effect engine oil consumption.
The Intake manifold vacuum [pre-turbo] acts against a spring loaded diaphragm to control the flow of crankcase gases (Figures 11-1 and 11-2). Higher intake vacuum (or highintake restriction, e.g. plugged air filter) levels pull the diaphragm closer to the top of the outlet tube. This reduces the vacuum level from getting to high in the crankcase. As the intake vacuum decreases, the spring pushes the diaphragm away from the top of the outlet tube to prevent crankcase pressure from going positive.


CDR Valve Test


Good Luck..