Rather long post, but if you think you have issues with power, boost, or MPG, this might prove a worthwhile read. Just thought I'd make a little info post for those here who might not be aware of the critical nature of the crossover pipe on the 6.5 It takes the exhaust from the drivers side manifold, passes under the engine, and up into the passenger side exhaust manifold where it meets the passenger side exhaust, and then feeds the turbo.
This can be a particularly problematic pipe on the 6.5 - they are exposed to quite a lot of road blast as well as road debris you might run over. Combine the two together (especially if you live in an area where they use salt on the roads in the winter months) your crossover could be leaking.
A leaking crossover will cause a few issues - lower boost, increased fuel consumption, and decreased power. A small leak might not even be easily evident unless you look under your engine, but sometimes (if the leak is bad) you can hear it when you pass another car or a concrete barrier on the side of the road while you have your foot into it - you'll hear a hissing or whooshing type noise being reflected from under your truck back up into your passenger side window.
A leak at the flanges (where the pipe meets the manifolds) will (without fail) leave black soot everywhere - usually it's the seal "donuts" that have failed and are no longer making a tight seal, but sometimes (as my pictures will show) the pipe can actually rot out at the flange.
Also not uncommon is the pipe rotting out completely. This can result in a "blow out" while you're driving (which is what happened to me) and then you loose a huge portion of your boost because of the hole in the pipe. If you happen to be towing at the time it's not much fun - ask me how I know.
The most dangerous situation is that your pipe is rotting in such a way that a flake of rust comes off inside the pipe and is ingested by the turbocharger - it can be a VERY expensive situation.
Lastly, a leaking crossover pipe on the passenger side flange can melt your starter wiring and be a potential fire hazard due to the heat and (if the leak is bad enough ) flames..
So, what to do? Crawl under your truck and inspect it - it's dead easy - check both ends at the flanges to see if there's any black soot - if there's soot, then you have a leak - could be simple (the donuts) or the pipe could be rotted at the flange itself.
Also, carefully inspect the full length of the pipe - check for any major rust or spots where it appears the pipe is thinning. Don't poke and prod too much with the truck not running as you don't want to accidentally push anything (if there IS a huge rust spot or hole) into the pipe for the turbo to suck it in.
In the end, if you see signs of leakage or impending failure, get the pipe replaced. It cost me about $90 for the pipe at the GM dealer. Preferably, replace it with a mandrel bent replacement from one of the aftermarket dealers, but in my case (and perhaps the case of others if time is a concern and you can't wait for a pipe to arrive in the mail) the GM pipe is available of course. The donuts were about $20 a piece from GM - replace them no matter what - no sense in putting on a new pipe onto to reinstall potentially leaky seals.
Doing the job yourself in your own driveway is a realistic option but beware of the bolts - the passenger side ones especially (due to the heat on that side) are notorious for seizing up and if you break one, it can get fun quick. In my case, I paid an exhaust shop for the replacement, and yes, one bolt DID end up breaking in the exhaust manifold so it tuned out to be money well spent.
The results? WOW, apparently my leak at the flange had been slowly getting worse (blowout aside) at a pace where I didn't really notice the slow loss of boost and power. With the new pipe on I can hear the turbo spool up with even light acceleration around town 3-5 PSI just pulling away from a red light. My power is back (both empty and towing) and I'm confident my MPG will see improvement as well since I was having to *really* hammer on it for onramp acceleration and even uphills in the city - towing, don't even ask - it was bad.
So, here's a few pics:
![Image]()
The above is the new crossover in place.
![Image]()
The old crossover with the "blow out" on the corner. This is a prime area where the road salt rusts the pipe as it's a thin spot (due to the bend).
![Image]()
The opposite corner of the pipe, also showing the impending rust hole - on inspection after we were all done I was able to stick a screwdriver through this spot with ease - another blowout wasn't far off.
Last but not least, the pic below was a "hidden" leak at the exhaust flange on the passenger side - you can see where the flange actually rusted out and exhaust was whistling through this hole because it had actually ate through and damaged the donut:
![Image]()
This can be a particularly problematic pipe on the 6.5 - they are exposed to quite a lot of road blast as well as road debris you might run over. Combine the two together (especially if you live in an area where they use salt on the roads in the winter months) your crossover could be leaking.
A leaking crossover will cause a few issues - lower boost, increased fuel consumption, and decreased power. A small leak might not even be easily evident unless you look under your engine, but sometimes (if the leak is bad) you can hear it when you pass another car or a concrete barrier on the side of the road while you have your foot into it - you'll hear a hissing or whooshing type noise being reflected from under your truck back up into your passenger side window.
A leak at the flanges (where the pipe meets the manifolds) will (without fail) leave black soot everywhere - usually it's the seal "donuts" that have failed and are no longer making a tight seal, but sometimes (as my pictures will show) the pipe can actually rot out at the flange.
Also not uncommon is the pipe rotting out completely. This can result in a "blow out" while you're driving (which is what happened to me) and then you loose a huge portion of your boost because of the hole in the pipe. If you happen to be towing at the time it's not much fun - ask me how I know.
The most dangerous situation is that your pipe is rotting in such a way that a flake of rust comes off inside the pipe and is ingested by the turbocharger - it can be a VERY expensive situation.
Lastly, a leaking crossover pipe on the passenger side flange can melt your starter wiring and be a potential fire hazard due to the heat and (if the leak is bad enough ) flames..
So, what to do? Crawl under your truck and inspect it - it's dead easy - check both ends at the flanges to see if there's any black soot - if there's soot, then you have a leak - could be simple (the donuts) or the pipe could be rotted at the flange itself.
Also, carefully inspect the full length of the pipe - check for any major rust or spots where it appears the pipe is thinning. Don't poke and prod too much with the truck not running as you don't want to accidentally push anything (if there IS a huge rust spot or hole) into the pipe for the turbo to suck it in.
In the end, if you see signs of leakage or impending failure, get the pipe replaced. It cost me about $90 for the pipe at the GM dealer. Preferably, replace it with a mandrel bent replacement from one of the aftermarket dealers, but in my case (and perhaps the case of others if time is a concern and you can't wait for a pipe to arrive in the mail) the GM pipe is available of course. The donuts were about $20 a piece from GM - replace them no matter what - no sense in putting on a new pipe onto to reinstall potentially leaky seals.
Doing the job yourself in your own driveway is a realistic option but beware of the bolts - the passenger side ones especially (due to the heat on that side) are notorious for seizing up and if you break one, it can get fun quick. In my case, I paid an exhaust shop for the replacement, and yes, one bolt DID end up breaking in the exhaust manifold so it tuned out to be money well spent.
The results? WOW, apparently my leak at the flange had been slowly getting worse (blowout aside) at a pace where I didn't really notice the slow loss of boost and power. With the new pipe on I can hear the turbo spool up with even light acceleration around town 3-5 PSI just pulling away from a red light. My power is back (both empty and towing) and I'm confident my MPG will see improvement as well since I was having to *really* hammer on it for onramp acceleration and even uphills in the city - towing, don't even ask - it was bad.
So, here's a few pics:
The above is the new crossover in place.
The old crossover with the "blow out" on the corner. This is a prime area where the road salt rusts the pipe as it's a thin spot (due to the bend).
The opposite corner of the pipe, also showing the impending rust hole - on inspection after we were all done I was able to stick a screwdriver through this spot with ease - another blowout wasn't far off.
Last but not least, the pic below was a "hidden" leak at the exhaust flange on the passenger side - you can see where the flange actually rusted out and exhaust was whistling through this hole because it had actually ate through and damaged the donut:
