POWER ROBBER - Diesel World


While the 6.4L Power Stroke offers what is arguably the best tuneronly performance in the diesel industry, it’s earned a reputation for a whole slew of premature failure points, not to mention expensive repair costs. It’s unfortunate, but ’08- 10 Fords that are subjected to day-in, day-out use often begin to experience substantial problems after the 100,000- mile mark—if they make it that far. At the forefront of this powerplant’s growing list of frequent problem areas are cracked up-pipes. Lack of power, exhaust fumes in the cab, audible whistling under acceleration, and a mess of soot along the firewall and transmission tunnel are all indicators of this failure, and we’ve got a textbook example to show you this time.


First things first, access had to be gained to replace the up-pipes. The techs here are accustomed to addressing up-pipe issues with the cab on the truck or by pulling the transmission, but for the sake of full disclosure other engine repairs were performed on this particular truck at this time—hence the company’s decision to go ahead and pull the cab. With the truck positioned where he eventually wanted it to be on a two-post lift, Chad Flynn popped the truck in Neutral and drained all engine coolant (shown). Leaving the transmission in Neutral gives him the option of maneuvering the truck by hand should the need arise.


After each battery’s positive and negative cables were disconnected, the fuse box power wire was removed from the driver side battery (shown). Then the smart junction box cable was loosened from the passenger-side battery and both batteries were pulled from the engine bay. Other items included laying the positive battery cables across the intercooler (as they go up with the cab), disconnecting the main starter cable, and unplugging the alternator cable (which stays with the frame).


Next, the truck’s filter minder was unplugged, its mass airflow (MAF) sensor removed, and the air intake assembly was pulled. This allowed Flynn access to the trigger wire for the starter, which was also disconnected.


Evacuating the A/C system was
next on Flynn’s to-do list (with the
system requiring a recharge at a later
time). Once that process was started,
he moved on to removing the engineto-
heater core hose, which was left
hanging over toward the passenger-side
fender well.


The work continued with Flynn unhooking the ground-to-cab strap from the firewall and unplugging the engine harness for the powertrain control module (shown). The engineto- cab wiring harness would also be disconnected at this time.


Because the intercooler, hotside intercooler pipe, and cold-side intercooler pipe go up with the cab, only the ends of the intercooler tubes that attach to the engine had to be loosened and separated. Here you can see that the cold-side intercooler pipe has been disconnected from the throttle body and tied to the radiator core support.


Both vacuum lines that actuate the front hubs for the truck’s four-wheel drive system were disconnected. Then the hood latch mechanism was removed for access to the transmission cooler line, which is located behind the passenger side of the front bumper. Once the transmission cooler line’s barbed fitting was pulled, it was allowed to drain a moment, and was then capped off to avoid dripping on Flynn while he was working (shown).


Once he’d disconnected the block heater, Flynn removed all air bleed lines from the degas bottle, separated the top radiator hose (shown) and anchored it back toward the engine via zip tie, and then anchored the low-pressure turbo side of the hotside intercooler pipe to the radiator core support. After that, the degas bottle was pulled from the engine bay, the heater core outlet hose was disconnected, and the passenger side battery tray was pulled.


Next, the brake master cylinder was removed from the firewall, and the three cab-to-chassis wire harnesses were located (just above the steering shaft) and disconnected. The brake master cylinder stays down with the engine so that no bleeding of the brakes will be necessary.


With the power steering pump-to-engine hose requiring removal in a cab removal job, things can get messy quickly. Believe it or not, Flynn positioned an old Cool Whip container under the power steering pump and drained a fair amount of fluid into it before capping off its port. From there, he disconnected the hydro boost-to-power steering lines up at the firewall, loosened the 13mm bolt in the steering shaft, and moved the top portion of the shaft down, toward the front axle.


To gain access to the nuts on the front cab mounts, both headlight assemblies were removed. Once they were out, the lower radiator hose was separated and the engine’s remaining coolant was flushed into a large oil pan.


Along the driver-side frame rail (just under the door) Flynn disconnected the emergency brake cable, as the front portion (shown) of the cable goes up with the cab while the rest of the cable stays down, along the frame. Next, Flynn freed the transmission shift cable from its respective shift lever, and made sure the transmission was still in Neutral.


After using a little bit of heat via acetylene torch, Flynn removed the front cab mount bolts via impact. The remaining cab mount bolts (inside the cab) were removed using a small butane torch to warm the nuts and the same impact and 15mm socket shown here. It’s important to heat up the nuts a bit prior to attempting to remove them, especially if they’ve never been out before (as Ford uses plenty of Loctite on the assembly line).


Positioning a lift pad at all four corners of the cab’s pinch welds, it was time to send the cab skyward. We’ll note that Flynn takes care to anchor the rear of the cab to its respective lift arm via ratchet strap to rule out the potential for the cab to tip forward while up in the air.


Finally, we were at the meat of the problem. With the cab off, the cracked passenger-side uppipe was fully exposed. You’re looking at a drive pressure leak. Without adequate drive pressure, you will have a low boost pressure scenario, which was exactly what the truck’s owner was experiencing for several hundred miles. Anytime you’ve got an exhaust leak on a diesel engine, it doesn’t take long to coat everything around it (or downwind of it) in soot. In this case, the transmission tunnel, fi rewall, and downpipe were covered in a thick layer of black, which helps explain why the owner noticed a faint exhaust smell creeping into the cab.


This is a typical failure point for a factory up-pipe: the bellow. Many believe that the bellows themselves (also referred to as the braided wire section or exhaust expansion joint) are not fl exible enough. As the engine moves, the rigidity of the bellows leads to excess stress and ultimately cracks them.


Before Flynn ever laid a hand on the up-pipes, all fasteners were soaked in penetrating oil. Flynn told us that he prefers to use an impact here to loosen the up-pipe nuts. In his experience, the quick jar that the impact provides tends to help break the nuts loose much easier than using a standard ratchet or wrench.


With the EGR crossover pipe (the tube that incorporates an engine oxidation catalyst and doubles as the passageway that exhaust gasses fl ow through on their way to the first EGR cooler) out of the way, Flynn removed the up-pipe to turbo collector bolts. He then disconnected the downpipe from the low-pressure turbo for more working space.


Using an impact and a 13mm socket (and after letting the nuts soak in penetrating oil for some time), Flynn backed off the driver side up-pipe to exhaust manifold nuts and removed the pipe. A 10mm socket would be required to remove the up-pipe to turbo collector bolts up top.


Then it was back to the impact, this time on the passenger side up-pipe nuts. We’ll note that all-new OE up-pipe gaskets were used during the job (PN 8C3Z-6N640-A).


Knowing that the exhaust collector bolts are notorious for stripping out or breaking off during removal, it pays to go with all-new fasteners in a job like this. Called a turbo hardware mounting kit by Ford (PN 8C3Z-9T514-C), it comes with six new 10mm up-pipe bolts and two up-pipe to turbo gaskets.

To rule out another up-pipe bellow from failing in the near future (and repeating the laborious task of pulling the cab or transmission), both up-pipes were replaced at this time. A brand-new OE driver side stainless steel up-pipe is shown (PN 8C3Z- 6K854-B).

Just like the driver side up-pipe, the passenger side unit (PN 8C3Z-6K854-A) came from the local Ford dealership. While there are heavy duty, off-road use up-pipe kits available in the aftermarket (as well as upgraded exhaust manifolds), the owner of this truck chose to continue using OE parts.


In addition to using all new up-pipe fasteners, Flynn generously coated the exhaust manifold studs and turbocollector bolts with anti-seize during installation. Here you can see the new passenger side up-pipe attached to the turbo collector, ready to be tightened down. These fasteners received a final torque spec of 18 ft-lb.


The EGR crossover pipe was reinstalled, along with a new up-pipe gasket at each end. All told, six up-pipe gaskets were required to complete the job (since only two are supplied in Ford’s turbo hardware mounting kit, four extras must be ordered separately).


The up-pipe gaskets (8C3Z-6N640-A) fit very tightly on the exhaust manifold studs. Flynn seats them by slowly walking the up-pipe nuts down toward the exhaust manifolds with a 13mm socket. All up-pipe to exhaust manifold nuts were eventually torqued to 23 ft-lb.


With the new up-pipes securely in place, the line of thought is that the truck will go at least another nine years before this issue surfaces again. If you ever have to venture this far into your ’08-10 Super Duty, we recommend you replace any items that appear questionable on the engine, or make the appropriate updates recommended by Ford. Case in point: While this engine was receiving new up-pipes, it was also being fitted with Ford’s updated high-pressure fuel pump wiring harness (PN 8C3Z-9G805-B).

If the cab-off procedure didn’t familiarize you with how most shops perform major engine repair(s) on the 6.0L Power Stroke, the 6.4L Power Stroke will. In the case of the ’08-10 Super Duty, there is even less breathing room under the hood, which means that half the battle is waged just trying to gain access to the parts. Anytime items such as turbochargers, head gaskets, the high-pressure fuel pump, or up-pipes need to be replaced, it’s common practice to lift the cab for easy access. While all those parts can be reached and fixed with the cab on the frame, it’s much easier to remove the cab for adequate working space. Follow along as we document Chad Flynn of Flynn’s Shop in Alexander, IL, lift the cab of an ’08 F-250 to fix its power-robbing exhaust leak.DW