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wrench buster

Hey there , I have a 2012 Freightliner M2 Cummins 8.3, and it has air escaping at the flange connecting at cooler to manifold connection. I installed a new gasket and it’s the same thing. I noticed there was LOTS of pressure when a disconnected the crossover tube from cooler to EGR cooler and the air leak stopped. It seems like the EGR valve was not flowing the EGR air to the intake. Can anyone shed some light on this situation.
I have a code for high DPF dif pressure.
Thanks

tree98

Start by doing an EGR tuneup, including making sure the EGR cooler and all associated piping isn't completely packed with soot.

wrench buster

All the piping is clean, all EGR Diff ports also, it seems like the turbo is pushing too much a EGR air into the connection at the EGR valve. I believe there are EGR pressure sensors , however I have no codes related to that. what do you think? When I pulled the EGR crossover tube off while it was running it had LOTS of pressure behind it. Maybe EGR stuck?

Rawze

(08-19-2025 )wrench buster Wrote: All the piping is clean, all EGR Diff ports also, it seems like the turbo is pushing too much a EGR air into the connection at the EGR valve. I believe there are EGR pressure sensors , however I have no codes related to that. what do you think? When I pulled the EGR crossover tube off while it was running it had LOTS of pressure behind it. Maybe EGR stuck?

Is this while engine is running?.

Is the engine de-mandated, or have any custom programming in it?... or everything is still in tact?. - YOur posts imply that everything is still in tact.

(non-deleted, factory programming)...
Those smaller engines have issues where the turbo will over-spool all the time, especially when the EGR cooler starts getting restrictive. they will also do it if the CAC is restrictive too (after-market unit, dusty, oily, etc). So will higher then normal exhaust pressures (partially clogged cans).

the turbo will also spool up higher than normal if the DPF is simply not warmed up all the way yet too.

tree98

The ECM commands all kinds of different pressure through the EGR circuit to the intake. You have no way of knowing how much is to much at any given time. I think your chasing your tale and following a rabbit hole with no end.

You said you have a code for high DPF differential pressure so start there. When is the last time the DPF was baked? What does aftertreatment history look like when connected with insite?

wrench buster

(08-19-2025 )Rawze Wrote: (non-deleted, factory programming)...
Is the engine de-mandated, or have any custom programming in it?... or everything is still in tact?. - YOur posts imply that everything is still in tact.

Those smaller engines have issues where the turbo will over-spool all the time, especially when the EGR cooler starts getting restrictive. they will also do it if the CAC is restrictive too (after-market unit, dusty, oily, etc). So will higher then normal exhaust pressures (partially clogged cans).

the turbo will also spool up higher than normal if the DPF is simply not warmed up all the way yet too.

Thanks for your reply, Yes this is with the engine running. EGR cooler is new. I keep getting a code for Hi DPF load, but that could mean lots of things. Engine is original no MODs

wrench buster

(08-19-2025 )tree98 Wrote: The ECM commands all kinds of different pressure through the EGR circuit to the intake. You have no way of knowing how much is to much at any given time. I think your chasing your tale and following a rabbit hole with no end.

You said you have a code for high DPF differential pressure so start there. When is the last time the DPF was baked? What does aftertreatment history look like when connected with insite?

The DPF was cleaned a couple of weeks ago. It is doing re-gens about every 10 hrs. according to Insite. Thanks for your reply. Let me know what to look for in the aftertreatment history if possible.

Rawze

(08-20-2025 )wrench buster Wrote: ...
The DPF was cleaned a couple of weeks ago. It is doing re-gens about every 10 hrs. according to Insite. Thanks for your reply. Let me know what to look for in the aftertreatment history if possible.

Was the DOC unit cleaned as well?.

How was the DPF cleaned?.

Did anyone bother to do a DPF replacement procedure in Insite when the clean one was installed?.

Was the Decomp tube inspected for clogging?.
info: https://rawze.com/forums/showthread.php?...07#pid1807

You said it was a new egr cooler.. is it an OEM unit?, or after-market?.

Does the turbo calm down when the DPF, temps etc. reach above 450-f so?.

What is the turbo position and engine rpm sitting at when its acting up?.

Rawze

(08-19-2025 )wrench buster Wrote: Hey there , I have a 2012 Freightliner M2 Cummins 8.3, and it has air escaping at the flange connecting at cooler to manifold connection. I installed a new gasket and it’s the same thing. I noticed there was LOTS of pressure when a disconnected the crossover tube from cooler to EGR cooler and the air leak stopped. It seems like the EGR valve was not flowing the EGR air to the intake. Can anyone shed some light on this situation.
I have a code for high DPF dif pressure.
Thanks

... And aside from the DPF faults... it is quite normal for the exhaust circuit (and parts of the egr circuit) to have quite a bit of pressure in it with engine is running. The exhaust manifold (and piping to the egr valve) can have as much as 80-90+ PSI pressure in it under full engine operating loads. If it is leaking at idle, then something is wrong with the pipe connection, gasket wrong, or something else, etc.