What does a buyer need to immediately do to a used Cummins DPF motor with regards to emission equipment?
Here are the steps I would go through with a truck owner who just purchased a used truck with an isx, say 08′-11′ CM871 for example, teaching them how to keep these systems healthy themselves,… I am only referring to the EGR/DPF here in this example, skipping other, more obvious things,…Lets also assume the truck has ~380k miles on it and has been neglected, outside of typical shop maint, but runs fairly well in its current condition (typical of a recently purchased used truck)…
First thing is first,…Determine the health of these systems and see what has already been done…
<> EGR cooler, Visual: Looking to see if it has ever been replaced. Replacements are typically silver in color, or show signs of being re-painted. If it HAS been replaced, this is a good sign. Failure rates on these are high during the truck’s first 180-200k mileage range, where the warranty will still cover it. They fail due to settling of the block during the engine break-in period, causing mechanical stress to the unit. Cummins Engineering, when I asked about this in 2010, informed me that it was an 80% failure rate, and that they did studies on loosening/re-tightening the bolts to relieve stress with little results. Replacement is more effective. After that first failure, re-occurrences are not common unless the engine suffers conditions that cause the block to ‘settle’ again, like say changing its governed speed by a large amount and driving it hard at the new speed. Regardless, keep a close eye on coolant levels, marking the tank at a given known coolant temperature.
<> DPF, Visual: Look for signs to see if it has been removed/replaced. If it HAS, this is a red flag. The DPF on a cummins is big enough to sustain a healthy exhaust flow for about 600k+ miles, where ASH, not soot or coolant, will finally cause it to read above 3.0hpa on a constant basis (above 3.0 costs fuel mileage). The only exception to this is if it gets cracked/damaged due to excess road stress or being impacted by road debris (not very common but can happen). Why then is it so common for it to fail or be replaced/cleaned before this mileage range?,…Outside problems, #1 being the after-treatment injector going bad, then second, a poorly running engine that produces a lot of excess soot, or a bad EGR cooler plugging it up with coolant. ALL of witch can be avoided, with good maintenance practices, long before it kills the DOC/DPF. If it has been replaced or cleaned at 380K miles or less, then it is highly likely there were, and are still problems with the engine/EGR system. Removing the DOC/DPF should only be a LAST-RESORT type item when everything else has been done to avoid it, and it is the only thing left, after replacing the injector/sensors with a new ones and force-regening it to determine its actual hpa.
<>Determine/Remove the soot buildup in the EGR system: Remove the IMAP sensor from the intake manifold. Very easy to do, takes less than a minute. If it is buried in soot, and it will be, at 250k+ miles, it is, at the very least, costing you fuel mileage by now, or at its worst, causing turbo problems, power loss, hesitation in the accelerator, and/or excess soot problems. You will get turbo actuator alarms long before you get alarms for this sensor being clogged. Many mechanics are fooled by this, chasing ghost problems in the much more expensive components like the turbo, egr valve, etc. I have the Insite software/ Fault tree software. On its best days, it is only about 30% accurate in dealing with these type of problems. The IMAP sensor, most of the time, can simply be cleaned using a dry toothbrush and NO chemicals. This one sensor has actually put many O/o’s out of business. I have witnessed trucks go from 4-mpg to 8-mpg, just from cleaning it.
Assuming it was in fact covered in soot, you will need several cans of ‘Carb and Choke’ cleaner. NOT ‘Brake cleaner’!!!. Brake cleaner turns everything into a soot magnet. You will have to remove the intake manifold, Venturi (egr mixer) pipe, and Delta-P crossover tubes, washing them out, to bring back the engine’s full fuel mileage potential and New-running glory. The Delta-P (EGR Differential Pressure Sensor), if it is the original from the factory (painted red), it will have to be replaced. It cannot be cleaned properly without it giving false readings afterwards. As this sensor clogs up, it causes EGR valve and EGR actuator alarms and problems, power loss, fuel mileage loss, and ‘turbo-coughing’ problems, quite often without ever throwing a code for the sensor.
<>Clean/Replace Exhaust Manifold Back-pressure sensor: This sensor usually lasts 400-600+k miles before giving problems. It can usually be just simply cleaned, along with its feeder tube, coming off the exhaust manifold. If it is going bad, the turbo will act up. Symptoms can be of,…Turbo-coughing, turbo-lag, actuator alarms, turbo overspin alarms, and/or even turbo inlet temperature alarms. This sensor can actually kill a turbocharger over time, and/or can cause a cracked head or gaskets from excess head pressures generated by the turbo acting up. This sensor can be checked with Cummins Insite software (original or cracked but working version at a decent price ) to see if is reading correctly if it is in question, but its a cheap sensor, so just replace it if its suspect.
<> The After-treatment injector (doser injector): It operates similar to a spray-can nozzle and is located at the turbo exhaust outlet. It is easy to inspect by simply removing the 2 exhaust clamps on either side of it and looking down into the pipe. They start clogging up at 250k+ miles like clockwork, even on engines that run well and have never been idled, causing many DPF and Regen problems when they do. They are easy to change, but only if your willing to drain your coolant into some buckets first (that kinda sucks). Yes it can be cleaned, and that helps the DPF a lot, but NO, most of the time, after cleaning it, will it last very long afterwards. It also costs you fuel and can leak coolant directly into your DPF as they go bad or fail. Not worth the risk of cleaning it if u ask me. The doser injector is also a money-maker for most of the dealers. They will almost always go straight for the DOC/DPF when you visit them, ignoring the injector because of the all-to-typical ‘DOC/DPF Face-Pluged alarm’ that is thrown by the engine, when there is little or nothing much wrong. The engine likes to throw this code way too easily, and many O/o’s fall victim to it when they visit the repair shop, many times, repeatedly, before the actual, more minor problem is found.
To sum all this up,…
every 250-300k miles,…
Remove and clean the IMAP sensor, Intake manifold, Venturi pipe, Delta-P crossover tubes, Exh. back-pressure sensor and feeder tube, and EGR temp. sensor.
Just replace the Delta-P sensor and After-Treatment injector. Then perform a DPF ‘Forced Regen’, ensuring the DPF is still below 3.0 hpa (it will almost always be below 2.0 hpa after a good cleaning by the regen with new after-treatment injector).
cost?,…$300-400 for after-treatment inj., $150-200 for Delta-P, 3 five-gallon buckets for holding your coolant, and a day of downtime, while drinking beer and getting very dirty. If you can change a spark plug for your car or lawn mower, then you are very likely capable of these things as well.
Can a shop do this for you?,…well,…possibly for a few thousand bucks. Not worth taking it to them if u ask me.
Ignoring it,…Countless truck problems, downtime, and thousands upon thousands in repair bills by the truck steeler(dealer) because they will blame the bigger ticket items either out of ignorance, or for extra profit. Most will laugh at you for mentioning simply cleaning these things instead of replacing them.
Maybe this helps someone out there who is already having issues,…Rawze.
BIG THANKS to Rawze from https://www.truckersforum.net/ shares his great thoughts with we all
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