The Freightliner Cascadia is a popular truck at my shop and on the highway, breakdown after breakdown I still enjoy working on them. Most are intimidated by their some what complicated fuel system and aggravating emissions system. Luckily I received an email from a fellow tech discussing these issues which may shed some light on what cause these issues I thought it was a great read and decided to share.
DDieselMonkey
So you’ve decided to buy that Cascadia, they are a decent ride with all that cabin space and storage, all the switches with their bells and whistles, little lights with many, many driver options to customize your home on the road. That cushy Legacy seat and cab suspension floats you down the highways.Daimler flaunts their powertrain package, base model comes in around 455hp with 1550ft lbs of torque grinding to the road that can be stepped up to a solid 500hp with 1750ft lbs of pulling power. To go even further the DD16 package pushes their full potential at 550hp and 1800ft lbs of torque for the heaviest loads.Gone are the days of your bullet proof 60s. In the decade I’ve spent at a dealer here is my break down of the breakdowns, the most common repairs I deal with.Every series has its own challenges, some have been overcome while others have sustained since the release of the DD platform.
Breaking Down Oil Leak Breakdowns
Injector line passthrough seals are the number one oil leak that plagues every model, it’s something Daimler just can’t seem to get right. This issue is more of an unsightly nuisance if anything as it’s an oil leak at the top of the driver side engine that coats everything when not taken care of promptly.There is an o-ring in the back of the head for the idler gear cover and bore caps in the cam housing, this one too is minor but can give the appearance of a leaking rear structure which is far and few between on these engines. The gear cover is a simple fix. If you have a good tech they will replace the cam cup plugs during a cam housing reseal.
The oil thermostat seals are prone to leaks up until a housing design change in the GHG17s. A simple fix but can soak the MCM when not attended to. The module itself may look bad but the leak is usually a culmination of the stat seal and screw plug, pressure sensor and passthroughs. Pan gaskets have been dripping down to the Gen5s (we’ll get to those in a bit). It hasn’t mattered type or how much silicone the corners of that pan gets, it will bleed.
The pan inserts have a bad habit of leaking, but this is initially caused from over torqued pan plugs, 35ft lbs should never require a 24″ 1/2″ ratchet to break loose but it’s usually the case. This can be fixed without dropping the pan but requires a special tool to remove the insert and is torqued back to about 75ft lbs with red loctite. Oil pressure sensors and injector harness seals have been sustaining issues as bad as the passthroughs, external and internal. The silicone pin seals break down and introduce oil into the engine harness that can possibly short out the MCM itself, the only true remedy for this is to replace the harness in severe cases.
The engine harness itself has a habit of breaking in the plastic trough across the front of the pan. Put that bolt back in the pan horn, you know which one I’m talking about. This issue is usually accompanied by EGR actuator short to high faults.
So lets get a bit more specific. In comes the EPA07, your cross of a 60s and Mercedes. I was working in a lube shop when these things came out. Getting this engine to hold prime after a simple service could be a nightmare and you could not use ether thanks to the intake heater grid adapted from the Mercedes. They were and still are tough engines. Clunky and a mechanical puzzle accessing different components through the layers of things that had to come off for simple jobs could be tedious. Even shortcuts are done weaving between tight spaced harnesses, hoses and lines. They are a fairly simple engine compared to what’s out now, 2 computers and lets roll.
The fuel doser pipe would constantly clog up not allowing regen temps to come up. If the s-pipe was clear the intake throttle valve is your next bet. They had the Delphi EGR actuators that would fail if you looked at them wrong. These were later replaced by early Sonzabons. The newer versions are much better and rarely have issues now, it comes as a retrofit kit. All in all, a dependable engine with the right tweaks.
Breaking Down EPA10 Breakdowns
Bring on the EPA10s and ACMs,the fuel doser pipe is still an issue with regen temps on these. They have the same design the predecessor had and soot loves to get right up in the nozzle cavity, Jake solenoids had an upgrade with these too, the green Jacobs were replaced with the grey Detroits. The excessive soot loads brought issues with the ventri ports, the poor design allows it to collect soot even worse than the doser port giving low air flow faults. You can manually clean them rolling a small drill bit between your fingers on the sensor side, a 90deg pick on the underside and a blow gun. This in turn can also affect the DOC face and clog the DPF filters. This was the series they actually brought out the Sonzebon EGR actuators that became the new standard resolving several old issues but this is still comparatively a dirty engine.
Injectors became a problem, not only smoking from over fuels but the fuel rail itself (commonly DD13s) had an inner lining that breaks down and instantly rusts internally if not kept wet leading to no starts because the injectors would clog when the debris would make its way to the internal needle valves. They have since fixed the rails and there is also a pre-tear down procedure that helps a lot that is still the recommended practice. Personally, if the injectors are going to be open for more than a few hours they are pulled and thrown in a bucket of fuel until reassembly. This tip was and still is important when the injector cup o-rings go out to help flush the coolant out of the internal workings. Simply, coolant equals rust. Torque spec and o-ring material changes have since been implemented and we don’t see this failure as much. You can verify this by blue or yellow o-rings now.
The DEF metering unit does little to help the extra soot build up. If you ask an engineer they will fault not draining the air tanks, both the DEF metering unit and pressure limiting valve are prone to rust build up just like the shift bar housings on the Eaton transmission. The lock tabs on the plastic piston of the PLV outlet often break. There is an after market filter kit you can install before the PLV to help keep moisture out. The phallic looking DEF doser nozzle also puts a whole new meaning to breaking it off in the box.
Overall the EPA10s are still pretty simple, the parts and software have hit their peak and we see less of these repairs now that terminals and drivers have figured out a maintenance routine.
Breaking Down GHG14 Breakdowns
Coming up the the GHG14s. While these gems made a lot of headway with past issues like the ITVs and doser pipes they came with more software and computer issues. CPCs dropped and is still fairly common. This is also the series Daimler claims they do not have an injector issue but an MCM issue and the new fuel maps took care of it. If this was really the case why’d the go from copper to stainless steel terminals? They also raise the amp and needle tolerance specs in the MCM. The overfuel in these are bad and will torch not only the engine but the aftertreatment with it. In the least it burns the lower liner o-ring or cracks the liner itself dumping coolant in the pan which ultimately is a new bottom end. The fuel issues do not end there as a change in the pump design removed the emergency lube line overheating the internals when fuel levels are low and throws metal from tank to tank. A lot of these are towed in fresh off the fuel isles. This repair requires and new pump and filter module, flushing the tanks and lines and if it’s not already there a frame mounted filter will be installed to aid in the fallout of debris in the aftermath.
If the injectors didn’t take the engine out the pickup manifold will by either blowing the side caps off starving the bearings of oil or the o-rings will simply turn to plastic no longer sealing the tubes. For the longest time every pan drop, even if just for a gasket, got new tube o-rings. They have changed the type of glue used on the pickup manifold side cap but this is still an issue. There is a nipple in the top of the oil filter standpipe that easily breaks as well if a technician is not watching (especially on a snub nose as the air filter is over top of it). This allows unfiltered oil directly into the galley that feeds the main bearings.
The aftertreatment took yet another hit in this series. Leaking DEF pumps at the filter seal or housing plugs, DEF buildup in the mixing chambers due to not enough air flow through the DPFs causing the DOC face to plug. This was fixed via installing an awning kit inside the box and a software update. Trucks that have high idle time (think construction site) would sometimes have their idle RPMs bumped up to 700 to aid in air flow across the the DOC face. If there is still a NOX issue the outlet sensor is the usual suspect,the platinum in the SCR catalyst just does not seem to hold up in these boxes neither.
Of the more minor faults of this series is the variable speed water pump, you can actually program this out through Detroit. 5V reference faults and leaks, limp mode will allow you to drive to the next stop if the pulley shaft doesn’t come out.The EGR cooler turbo side flange has a habit of cracking and blowing off, not much you can do about this either.
Breaking Down GHG17 Breakdowns
I’m throwing GHG17 and GHG21s together here, they’re essentially the same engine minus software. Only 2 main electrical issues but both will shut you down being CAN Communication faults. There’s a bracket at the air compressor that chews through wires taking out the transmission datalink, on average it’s about a 3hr repair. A lot of times the bracket is removed by the technician but then there’s nothing to secure the harness to and it chaffes on the compressor coolant line instead, don’t do that, use heater hose and add an extra zip tie or 2. There’s 2 more spots for TCM datalink failures at the bellhousing and across to top of the TCM. There is an ACM datalink issue at the ACM in the drip loop for the 21pin that vibrates against the cover inside the rigid loom and occasionally in the bundle that runs up the side to chassis interface plugs. The chassis harness wrap has been updated to help prevent this from happening as often. I call it gator wrap, it’s a thicker, almost rubber like over the fabric wrap.
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DEF pumps, inlet NOX sensors, injectors smoking and oil manifolds are still an issue as well as air filters which are critical to prevent liner dust out/glazing, no cross hatching in the upper liner, the fire zone. Now to get up to date,while the Gen5s have come a very long way, the failures are catastrophic. The cam seal of this series holds up pretty well. The pass-throughs, even with a different shaped feed line, did not help there and are the usual culprit of top end oil leaks. The new style oil pans don’t leak as bad but they now blow the pressed in plug inserts out, the only sure fire remedy for this is to get the aluminum pan option, also be sure to keep a cup of extra pan bolts around as they fall out when removed and are easily lost.
The single exhaust rocker arm finally has a service bulletin to replace with ones that allow more oil flow to the valve screws. While this has helped the 17000 trucks affected by this, we are still seeing them. This failure usually takes out the wrist pin in that cylinder,and if you’re lucky the rod comes out to say hello. Don’t force this, we can see how long you drove, your road speed and RPMs at the time of event, warranty will deny the claim. If it isn’t the wrist pin it’s an isolated failure in the rod bearing itself and you no longer get a new long block unless there’s actual block damage.
The repair is a rebuild from the crank shaft out and if it’s warranty they will only replace the affected component now. We have one on the floor as I write, spun all 6 rods, no mains, no liner or piston damage so it goes back with everything removed. New crankshaft, rods and gaskets, that’s it.
EGR coolers are still cracking at the end cap welds,the engineers claim this to be a torque procedure fallacy, gain there’s not much you can do about this. Simple repair but these parts are usually on national backorder with no ship dates. A newer issue of upper liner o-rings gives the affect of pushing coolant like a cooler failure,this is usually accompanied with an external head gasket leak on the exhaust side. This does require a special tool to test. I am flooded with this repair and has been coined “an o-ring inframe” as the head comes off, that cylinder comes out, 2 o-rings go in and reassemble.
Extended warranties are critical to these engines, EW4 will cover everything up to 500k miles when the big name fleets are usually selling off for new units. You can get warranties further than that and I would on select assemblies. EW2 will cover most external components like the air compressor and water pump but the 3 big ones, major components (this covers base engine failures), ATD (a one box ain’t cheap), and injectors (we can almost always blame an injector and get contingent damage, it’s an out). The 750k mile option on those 3 will usually suffice the life of the truck.