What causes Coking?
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Fleet Mechanic
Joined: Jan 2007
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From: Circle City
What causes Coking?
Vehicle maintenance, turbo, oil, fuel, air induction, all have an effect on coking.
EGR valve replacement/ cleaning is related to the occurrence of coking , the original causes should be corrected or the coking will reoccur.
There are TSB's related to coking and other diesel operating systems that could contribute to coking of the intake system, EGR valve specifically.
If the root cause of coking is related to one or a combination of the above, it would be nice to understand how to address the coking build up in the intake.
What are some of the TSB's that are related to the root cause of this effect, and how can we reduce this nuisance?
EGR valve replacement/ cleaning is related to the occurrence of coking , the original causes should be corrected or the coking will reoccur.
There are TSB's related to coking and other diesel operating systems that could contribute to coking of the intake system, EGR valve specifically.
If the root cause of coking is related to one or a combination of the above, it would be nice to understand how to address the coking build up in the intake.
What are some of the TSB's that are related to the root cause of this effect, and how can we reduce this nuisance?
Fleet Owner
Joined: Nov 2003
Posts: 27,923
Likes: 3,640
TSB on coking:
TSB 08-2-7
Coking deposits are generally un-combusted or incompletely combusted hydrocarbons and can form on system components such as the EGR valve, EGR cooler, EBP Sensor, EBP tube, intake manifold, turbo charger, catalytic converter and EGR throttle plate. Deposit sample analysis from warranty return parts confirms the source as engine oil or diesel fuel. Visual inspection CAN NOT link the sources of coking deposits as either from engine oil or diesel fuel. Coking deposits can be identified as shiny black grease like sludge, hard flat black solid mass, or thin light brown sticky layer.
Un-combusted deposits can be linked to delayed combustion events. Delayed combustion events can be a function of hard to ignite elements (poor quality fuel, excessive fuel, engine oil or excessive exhaust gas recirculation) in the combustion chamber or a delayed injection event (calibration, wire chafe, injector mechanical issue). Un-combusted fuel is usually evident as fuel scented white exhaust smoke. Un-combusted fuel may create coking which impairs system functionality eventually leading to black exhaust smoke/poorly combusted fuel.
Also (might be helpful):
Symptom Chart Index
http://www.motorcraftservice.com/ren...e=EN&viewer=IE
TSB 08-2-7
Coking deposits are generally un-combusted or incompletely combusted hydrocarbons and can form on system components such as the EGR valve, EGR cooler, EBP Sensor, EBP tube, intake manifold, turbo charger, catalytic converter and EGR throttle plate. Deposit sample analysis from warranty return parts confirms the source as engine oil or diesel fuel. Visual inspection CAN NOT link the sources of coking deposits as either from engine oil or diesel fuel. Coking deposits can be identified as shiny black grease like sludge, hard flat black solid mass, or thin light brown sticky layer.
Un-combusted deposits can be linked to delayed combustion events. Delayed combustion events can be a function of hard to ignite elements (poor quality fuel, excessive fuel, engine oil or excessive exhaust gas recirculation) in the combustion chamber or a delayed injection event (calibration, wire chafe, injector mechanical issue). Un-combusted fuel is usually evident as fuel scented white exhaust smoke. Un-combusted fuel may create coking which impairs system functionality eventually leading to black exhaust smoke/poorly combusted fuel.
Also (might be helpful):
Symptom Chart Index
http://www.motorcraftservice.com/ren...e=EN&viewer=IE
Fleet Owner
Joined: Nov 2003
Posts: 27,923
Likes: 3,640
Thread Starter
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Fleet Mechanic
Joined: Jan 2007
Posts: 1,708
Likes: 7
From: Circle City
What I get out of this whole coking problem is that it is directly induced via the egr cooler/ valve circuit. Is this correct?
So, if the "y" portion of the exhaust up-pipe was removed, then there is no way for these deposits to enter the intake circuit, right? Now this won't eliminate fouling in the turbo but the temperatures of hot exhaust gasses hopefully will keep coking in the turbo at bay.
So, will the elimination of the egr cooler circuit by physically disconnecting the exhaust flow at this connection have a significant effect on eliminating the coking build up?
I don't know of any other remedy. Maybe someone out their has another viewpoint.
So, if the "y" portion of the exhaust up-pipe was removed, then there is no way for these deposits to enter the intake circuit, right? Now this won't eliminate fouling in the turbo but the temperatures of hot exhaust gasses hopefully will keep coking in the turbo at bay.
So, will the elimination of the egr cooler circuit by physically disconnecting the exhaust flow at this connection have a significant effect on eliminating the coking build up?
I don't know of any other remedy. Maybe someone out their has another viewpoint.
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