paulkno
New Member
- Joined
- Apr 3, 2017
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- Location
- Manchester
- Your Mercedes
- S-Class W220 2002 320CDI
I've seen lots of talk about this but no solid solutions, just a lot of possibilities. So I thought I'd share mine.
Essentially I was solving the lack of power problem that many cdi owners talk of. The symptoms are the car is driving normally then when you demand more power the car just trundles along and hardly accelerates. It may rev up but your don't really go anywhere and have a serious lack of torque. If you stop and turn the engine off and on again it drives fine, for a little while. If you never asked for serious power you could drive for miles without noticing there was a problem. Then as soon as you go to pull onto the motorway or overtake something you realise there is absolutely no power.
Many owners talk of EGR problems and limp modes. However in this case there is no error msg or code stored to be read. ie this is not limp mode and the car is assuming that all sensory data is correct.
The EGR valve on this 320cdi engine is vacuum operated. I opened up the valve and of course it was well clogged with soot. It is totally possible to clean and free up the EGR valve. Very easy to access on top of the inlet manifold with only three torx screws holding it together. It's worth noting that the valve is in the mixing chamber and not the removable vacuum operated actuator. Both will need cleaning and freeing up. I figured if these were clogged then the inlet manifold is sure to be also.
There is a solenoid on the bottom of the inlet manifold that operates flaps inside. You can check the operation of this by manually moving the solenoid and seeing if it moves freely. Chances are if your inlet is clogged then the flaps won't budge and/or the ball and socket joint on the solenoid has slipped off while it was trying to open the jammed flaps. A sure sign you have a clogged manifold. This vehicle had done approx 140k miles and is a 2002 S-class.
I removed the entire manifold assy. I did this from above without ramps, however I wouldn't recommend it. It's a long fiddly job with very restricted access. The fuel rail and filter will need to be partially removed for access. Also there are 8 wires routed between the manifold pipes, so you'll have to unplug all these. One goes to the gearbox, another is an earth for the starter motor, another to the manifold pressure sensor and one to the (I'm gonna call it a water pump) I'm not sure exactly what it does but I'd love to so if you know... it is mounted to the underside of the inlet manifold and brings water through the egr cooler. This will also have to be disconnected and removed. Very tricky from above with spring clips holding the water pipes on. The EGR cooler also has to come off, don't drop the gasket at the exhaust end, the down pipe and EGR end are push fit. Then at the front there are further wires to the oil level sender on the sump (has to be unplugged from underneath, you don't need ramps but the trays will have to come off. Although you've probably already removed these to collect all the screws and ratchets you've dropped). Now theres a wire to the solenoid, another to what I think is a unit to do with the brakes or water system (can't remember off the top of my head but its NSF corner). And a finally a wire to the sensor on the air pipe from the turbo side.
Once you've removed all the torx nuts holding the manifold on you can wriggle it out and you'll probably find its almost totally clogged. Out of all the inlets this one only had about three that weren't blocked and the flaps we're totally jammed.
I cleaned it all out, freed up the flaps and refitted. Now it pulls like a train all the time.
Once refitted the engine will need repeated cranking as the fuel was disconnected. Make sure you have a battery boost handy, eventually it WILL start. You'll also need to top up the coolant as you'll have lost some from the weird water pump thingy mounted to the bottom of the inlet.
Unless you are fairly competent, have good tooling and are brave, I wouldn't recommend doing this job at home. If you have access to ramps or a pit, its much easier.
Basically if you have these symptoms, check the vacuum to the EGR valve. Clean the EGR valve. Check the inlet flaps can move. If the inlet is blocked ask your mechanic to remove it and clean it or if you're made of money replace the lot, but the valve on its own from Mercedes is £575. I expect the inlet manifold isn't much cheaper.
You could also try changing the airflow meter and air pressure sensor, as they're cheap. However these tend produce slightly different symptoms.
This is not the first W220 S320 CDI I've seen with this exact issue. In all cases its been a clogged up inlet system with jammed swirl flaps due to the EGR valve.
Hope this helps some people. Enjoy
Essentially I was solving the lack of power problem that many cdi owners talk of. The symptoms are the car is driving normally then when you demand more power the car just trundles along and hardly accelerates. It may rev up but your don't really go anywhere and have a serious lack of torque. If you stop and turn the engine off and on again it drives fine, for a little while. If you never asked for serious power you could drive for miles without noticing there was a problem. Then as soon as you go to pull onto the motorway or overtake something you realise there is absolutely no power.
Many owners talk of EGR problems and limp modes. However in this case there is no error msg or code stored to be read. ie this is not limp mode and the car is assuming that all sensory data is correct.
The EGR valve on this 320cdi engine is vacuum operated. I opened up the valve and of course it was well clogged with soot. It is totally possible to clean and free up the EGR valve. Very easy to access on top of the inlet manifold with only three torx screws holding it together. It's worth noting that the valve is in the mixing chamber and not the removable vacuum operated actuator. Both will need cleaning and freeing up. I figured if these were clogged then the inlet manifold is sure to be also.
There is a solenoid on the bottom of the inlet manifold that operates flaps inside. You can check the operation of this by manually moving the solenoid and seeing if it moves freely. Chances are if your inlet is clogged then the flaps won't budge and/or the ball and socket joint on the solenoid has slipped off while it was trying to open the jammed flaps. A sure sign you have a clogged manifold. This vehicle had done approx 140k miles and is a 2002 S-class.
I removed the entire manifold assy. I did this from above without ramps, however I wouldn't recommend it. It's a long fiddly job with very restricted access. The fuel rail and filter will need to be partially removed for access. Also there are 8 wires routed between the manifold pipes, so you'll have to unplug all these. One goes to the gearbox, another is an earth for the starter motor, another to the manifold pressure sensor and one to the (I'm gonna call it a water pump) I'm not sure exactly what it does but I'd love to so if you know... it is mounted to the underside of the inlet manifold and brings water through the egr cooler. This will also have to be disconnected and removed. Very tricky from above with spring clips holding the water pipes on. The EGR cooler also has to come off, don't drop the gasket at the exhaust end, the down pipe and EGR end are push fit. Then at the front there are further wires to the oil level sender on the sump (has to be unplugged from underneath, you don't need ramps but the trays will have to come off. Although you've probably already removed these to collect all the screws and ratchets you've dropped). Now theres a wire to the solenoid, another to what I think is a unit to do with the brakes or water system (can't remember off the top of my head but its NSF corner). And a finally a wire to the sensor on the air pipe from the turbo side.
Once you've removed all the torx nuts holding the manifold on you can wriggle it out and you'll probably find its almost totally clogged. Out of all the inlets this one only had about three that weren't blocked and the flaps we're totally jammed.
I cleaned it all out, freed up the flaps and refitted. Now it pulls like a train all the time.
Once refitted the engine will need repeated cranking as the fuel was disconnected. Make sure you have a battery boost handy, eventually it WILL start. You'll also need to top up the coolant as you'll have lost some from the weird water pump thingy mounted to the bottom of the inlet.
Unless you are fairly competent, have good tooling and are brave, I wouldn't recommend doing this job at home. If you have access to ramps or a pit, its much easier.
Basically if you have these symptoms, check the vacuum to the EGR valve. Clean the EGR valve. Check the inlet flaps can move. If the inlet is blocked ask your mechanic to remove it and clean it or if you're made of money replace the lot, but the valve on its own from Mercedes is £575. I expect the inlet manifold isn't much cheaper.
You could also try changing the airflow meter and air pressure sensor, as they're cheap. However these tend produce slightly different symptoms.
This is not the first W220 S320 CDI I've seen with this exact issue. In all cases its been a clogged up inlet system with jammed swirl flaps due to the EGR valve.
Hope this helps some people. Enjoy