6.5 turbo diesel chevy boost issue

Slut99

Slut99

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Joined
May 17, 2013
Location
Winston-Salem, North Carolina
My first question is. Is it possible for the EGR to bleed boost pressure off?


Ok here is my issue. I have a 1998 chevy 6.5 turbo diesel (yes it's a fucking beast) I use the truck to hual my 1 ton rig and it pulls great but some times it will lose all boost pressure like the WG is opening up and it will (Roll ALOT of coal) I know some of you are like fuck yes Cooter Roal the coal for the honeys. But iv tried to clamp the WG shut and it will do the same thing. So the only other place I'm thinking it could lose pressure is the EGR? is that possible? I don't know much about 6.5s when your driving it it will do fine for awhile then lose boost then do fine again and so on....
 
I don't know much specifically about that engine, but for general troubleshooting of a boost leak it's exactly the same as any other turbo diesel.

Sticky wastegate actuator, sticky wastegate flapper, exhaust leak between the engine and the turbo, intake leak between the turbo and engine, bad boost solenoid, vacuum leak. Possibly EGR seals, yeah. For the age of the engine and all the hoses, it could be any of those things. Look for the easy things first, like cracked or loose couplers, elbows, etc., between the turbo and the engine, and any signs of exhaust leaks before the turbo, and cracked vac lines.

Wiring the wastegate shut won't necessarily tell you anything if it's stuck, because you're just wiring it at whatever position it's stuck at (not necessarily closed), and it's hard to constrain it enough to actually trust that it's shut or that it isn't moving when you think it's not. Plus, it's a terrible idea because then you have no exhaust bypass and therefore no boost control. Kinda dangerous if everything works properly at the wrong moment.


Not getting any fault codes at all?
 
Sounds a lot like a wastegate solenoid or vacuum issue. The wastegate is held shut by vacuum in the 6.5l iirc, blocking the hose would cause the symptom, and the turbomaster setup for those uses quite a bit of spring pressure to hold the gate shut. Egr definitely can cause similar symptoms.

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Fabrik8 said:
I don't know much specifically about that engine, but for general troubleshooting of a boost leak it's exactly the same as any other turbo diesel.

Sticky wastegate actuator, sticky wastegate flapper, exhaust leak between the engine and the turbo, intake leak between the turbo and engine, bad boost solenoid, vacuum leak. Possibly EGR seals, yeah. For the age of the engine and all the hoses, it could be any of those things. Look for the easy things first, like cracked or loose couplers, elbows, etc., between the turbo and the engine, and any signs of exhaust leaks before the turbo, and cracked vac lines.

Wiring the wastegate shut won't necessarily tell you anything if it's stuck, because you're just wiring it at whatever position it's stuck at (not necessarily closed), and it's hard to constrain it enough to actually trust that it's shut or that it isn't moving when you think it's not. Plus, it's a terrible idea because then you have no exhaust bypass and therefore no boost control. Kinda dangerous if everything works properly at the wrong moment.


Not getting any fault codes at all?
Click to expand...



It's not leaking anywhere becauseit acts fine then it will lose boost then it will act fine and so on.

I clamped the WG SHUT with vice grips so it would not let any boost out seeing if that was the issue. Pretty sure it's not a WG issue. So only thing left is EGR???
 
mysterync said:
Sounds a lot like a wastegate solenoid or vacuum issue. The wastegate is held shut by vacuum in the 6.5l iirc, blocking the hose would cause the symptom, and the turbomaster setup for those uses quite a bit of spring pressure to hold the gate shut. Egr definitely can cause similar symptoms.


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Click to expand...


I believe it's the egr will the egr allow boost to bleed off?

Any easy cheap way of blocking erg off on a 6.5? Iv looked for block off plates nothing is offered the market sucks for 6.5s
 
BTW, have you taken off the turbo and checked the normal stuff like how free the wastegate pivot is, whether the wastegate sticks open, and whether there is any compressor or turbine wheel damage, or excessive shaft play? That's always a good sanity check.
 
It's been many years since I have owned a 6.5 truck but if I had to take a wild guess I'd say the vacuum pump is going out. Those motors are capable of a lot more than they got credit for if you do cooling system upgrades big injectors and a 4" exaust. I had one that would hang with a stock common rail Cummins with a lot better fuel mileage .

BUCKEYE PERFORMANCE INC.
828-779-2242
 
Slut99 said:
I believe it's the egr will the egr allow boost to bleed off?

Any easy cheap way of blocking erg off on a 6.5? Iv looked for block off plates nothing is offered the market sucks for 6.5s
Click to expand...
See if ss diesel supply still has parts for them.

BUCKEYE PERFORMANCE INC.
828-779-2242
 
Slut99 said:
It's not leaking anywhere becauseit acts fine then it will lose boost then it will act fine and so on.

I clamped the WG SHUT with vice grips so it would not let any boost out seeing if that was the issue. Pretty sure it's not a WG issue. So only thing left is EGR???
Click to expand...
So your saying you clamped vice grips on the actuator rod with it closed? (vacuum applied to actuator).
The egr if it is opening intermittently almost always sets a code due to system design. It's a normally vented system which opens the egr valve when vacuum is applied.

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Last edited:
mysterync said:
So your saying you clamped vice grips on the actuator rod with it closed? (vacuum applied to actuator).
The egr if it is opening intermittently almost always sets a code due to system design. It's a normally vented system which opens the egr valve when vacuum is applied.

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Click to expand...


So if I take the vacuum off the EGR it will stay crossed the whole time and not alow boost to escape
 
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