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Diesel  Exhaust Stage Repair

IF you own a modern common rail diesel, you will visit this subject at some time or another. If you have been directed here, you likely have codes, performance issues, and a good bit of worry. This page will help to explain the EGR, and Aftercare of the modern diesel, and our approach to getting you back to normal. Driving a powerful, efficient, long running diesel. 

Modern Diesel Common Rail

EGR and Exhaust Aftercare Stage Repair


Exhaust and exhaust aftercare has become a big deal. It can often be the biggest maintenance and repair cost of the entire life cycle of your diesel. Sure, a dealership for your unit can fix it. But the aftermarket has learned some tricks too. Understanding the difference is important. Below is our Stage approach to this problem.


We will address EGR first. In most diesels, EGR controls NOX emissions, and is used to stabilize, and control idle state. It is nearly always flowing. that means, you are getting carbon rich exhaust gasses reintroduced into the intake…..all the time. And, it has to go through a lot of components to do this. Most of all, a cooler. It gets plugged. It cracks, it leaks, it can be very unhappy when it gets dirty. Best practice….Clean it. clean it a lot. The dealer just wont do this. they wont even advise it. We do. ( This is another article ). You are reading this because, now, it is too late. EGR is coding, coolant is going away, something is wrong.
















Stage 1 EGR


Stage 1 always includes a good diagnosis. Get the codes, numbers. Get a good story/history. Do a good visual inspection. Check data, see if it tells us anything important.

Next, consider service, cleaning. BG services do a great job cleaning all but a completely plugged cooler. Will it fix it? NO. It is a service. It is a service as an attempt to repair. Success rate is very high, but it is still a service. It will clean it, and the flow path that EGR involves. Stage 1 may also involve other minor repairs, like clamp leaks, external coolant leaks, or a single sensor. EGR can have 3-4 sensors. At the end of Stage 1, reset and testing is in order. This all take a good bit if time. (2-4 hours) We start with a set amount, but don’t be surprised, even on Stage 1 if we ask for a bit more time.


Stage 2 EGR

Stage 2 Means Stage 1 did not finish the job. It does not mean we did nothing. We did a lot. diagnose, cleaning, baseline, all needed. All valuable. But, we are not done. We only go to Stage 2 after doing some, or all of stage one. Stage 2 usually means replacing a major component. a cooler, an actuator, or multiple sensors. Replacing the cooler assembly is common. It can get very plugged, or leak coolant, or almost anything else. Lots of heat and carbon going on there. Some engines have 2 coolers, and are very complex.

Stage 3 EGR

Stage 3….Replace everything!!!.. kind of. Really, what it means is, the intake, or other major unit that has been burned up or plugged so bad, it will need replaced. Intakes are the most common. It is stage 3 for a reason. It can get ugly.

Final notes

Remember, stage repair is cumulative. Meaning, NO, we don’t give a refund on stage 1, or 2. We do real effective work with real value. We usually know sooner than later if the Intake is beyond repair, but we will have good discussions with you before that happens.

Stage 1 Exhaust Aftercare

Stage 1 starts with good diagnosis, with factory scan tool data. Testing, data, physical inspection, and more. This is a complex system, with really, three stages of its own. Stage 1 may lead to simple, single sensor, or actuator repair, or attempts at servicing. (BG Services) On all Bosch Aftercare systems, we will likely perform at least one manual regen. This throws a lot of diesel fuel, and heat downstream to try to “cook” the carbon off. Will it work? Unknown. True that. If the system is coding for plugged SCR, or Cat efficiency, the success rate is 50/50. Really, the dealership may not do most of what we do on stage 1, they will just replace everything, ($6,ooo). We can do that too. But, at least, we have an option 2, and 3. The BG cleaning services we perform do clean all the way downstream. Any cleaning service has it’s limits. (BTW, BG is by far the best) But even a partial success can save thousands. So, understand, this is stage one, the services, and some repairs do some good. but, repairing one system to function, can expose an hither-too before untested system. We may not be done. some extensive test driving can be in order, and sometimes, we at the shop cannot do all the test driving needed. You may be doing that.


Stage 2

Stage 2 is next steps. Again, we can do some things the dealer wont try. Most importantly, we can cook it! Heating up the Cat, or SCR to a very specific temperature can clean the coked on carbon, leaving behind a clean porcelain substraight, and not damaging the rare earth metals that are washed onto the platelets. This process is done all the time now. Tested, and perfected on HD trucks. (HD Cats can be $10,000) The unit is bench flowed, and weighed to determine if cleaning has done a thorough enough cleaning to reassemble. Will it work on your car? It is at least 50/50. But statistically, success is well over 80%. Cooking costs 3-600$, plus labor. Be careful when deciding to do this. No, we cannot refund this cost. If you want a sure thing…do not pass go, go directly to Stage 3. 

Also included in stage 2, replacing multiple actuators, sensors, and even one of the major units, Cat, SCR. And Module updating.


Stage 3

Basically, Yes, replace everything. Mainly, the Cat, and SCR. Sensors that are even suspect must be done, DEF actuator, tank, hosing must be in working order when done. There are multiple modules to run this system, and they may need updated.

The good thing about this system, is when it is running right, a modern, powerful, efficient diesel can be very, very clean and safe.

See the Diesel Maintenance page to learn more about keeping this from happening in the first place. ( Yes, it can be done)

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