Turbo Diesel Loosing Boost
07-30-2020, 01:45 PM
#1
Senior Member
Thread Starter
Join Date: Nov 2005
Location: Morehead, KY USA
Posts: 396
Likes: 0
Received 3 Likes
on
2 Posts
SLK55 AMG, E320 BlueTec, ML350, (formerly) C32 AMG, MR2 Turbo, HD-FLH-FSE, BMW R100RS, Ducati M900
Turbo Diesel Loosing Boost
I have a 2007 E320 Bluetec V6 Turbo Diesel sedan. My understanding of the design of the MB turbo bypass system is that it is electronically controlled. This is new to me. My other turbo vehicles used actuators which were opened and closed by boost pressure, vacuum, spring pressure, etc. My Benz runs good but is getting long in the tooth with 205k miles on the clock. I have had intermittent issues where the car looses manifold pressure for no apparent reason. Most often this occurs when it is hot outside and the car is running in a stop and go situation where it may be on boost and then suddenly I have to let off the throttle to slow or stop which may activate the inlet bypass to recirculate excess boost. When this happens it does not throw a code or CEL and it usually does not go back to normal until I stop the car and remove the key. If I don't do that, it limps along with about 1/3rd of the normal power, barely able to get out of its own way.
I can usually, turn it off, remove the key and immediately restart the car and it goes back to normal in some manner resetting whatever is malfunctioning. I am looking for ideas for either relays, actuators or sensors which may be a common source of this sort of failure and where they are located. I do not suspect a bad turbocharger for these reasons: A bad TC bearing is not going to reset. If the impeller is seized it will likely stay that way. A bad waste gate is the same but if the actuator is bad?? That could be the issue. I would think that if it was the waste gate stuck open only, that running wide open would still make some boost. I see no evidence of that at present. This issue has gone on for 18 months and I drive this car daily for a 125 mi round trip commute and it is still going strong. A bad TC would have failed completely by now. Photos and schematics are appreciated. I have been driving turbo vehicles for 35yrs and am a engineer so, I am fairly tech savvy but would appreciate knowledgeable advice to aid troubleshooting. Note that this is not an everyday occurrence. More like once or twice a month.
Irish
I can usually, turn it off, remove the key and immediately restart the car and it goes back to normal in some manner resetting whatever is malfunctioning. I am looking for ideas for either relays, actuators or sensors which may be a common source of this sort of failure and where they are located. I do not suspect a bad turbocharger for these reasons: A bad TC bearing is not going to reset. If the impeller is seized it will likely stay that way. A bad waste gate is the same but if the actuator is bad?? That could be the issue. I would think that if it was the waste gate stuck open only, that running wide open would still make some boost. I see no evidence of that at present. This issue has gone on for 18 months and I drive this car daily for a 125 mi round trip commute and it is still going strong. A bad TC would have failed completely by now. Photos and schematics are appreciated. I have been driving turbo vehicles for 35yrs and am a engineer so, I am fairly tech savvy but would appreciate knowledgeable advice to aid troubleshooting. Note that this is not an everyday occurrence. More like once or twice a month.
Irish
