Turbo Boost problems. 406 HDI 2000

In the old days the turbo would boost as soon as the engine speed was sufficiently high and any over pressure would be dumped by a relief valve or controlled by a wastegate.



In these modern times of electronics the turbo wastegate is normally open instead of normally closed so there is no automatic boost. The engine management system decides when there will be boost and how much boost there will be.



Turbo chargers are amazingly reliable unless they are abused or there has been foreign matter ingress. When looking for the cause of no boost it is wise to disconnect the intake trunking and turn the compressor vanes by hand to ensure all is well.



Disconnect the vacuum line to the wastegate servo and apply suction to the servo to ensure the servo, the linkage and wastegate is moving and in good order.



The next stage is to examine the vacuum line and connections back to source and then ensure the vacuum supply is adequate.



If all is found to be well with those physical checks the cause of no boost is either the failure of one of the vacuum switches (or the electrical wiring or connections to them) or a fault condition exists that has caused the engine management to decide not to provide turbo boost.



In that case diagnostic equipment will be needed.

I am sorry but we have no way to cross reference that information, contact the MB dealer parts dept to verify, but off the top of my head i would say no, the Germans would not make it that easy.

ur bacyard mech may hav done things bacward--u need a haynes or some other repair manual/turbo book--scan car using tech II with a data stream for precise solution

I assume its the 6.0L diesel...If so sigh......double sigh.. I had one of these...triple sigh. I need a bit more clarification. How many km on the engine/vehicle. Also, you say that it blows black smoke while running at a constant speed at 2600 rpm, or while you are accelerating to 2600 rpm. Also, when you say the boost goes down, does it decrease by itself, or when the throttle is let off. The boost naturally goes down when the throttle is released (not trying to be a ****, i dont know how much you know). However, if the boost is going down by itself, while the engine is under load (its not supposed to, it should stay constant) it could be a couple of things, which "can" contribute to black smoke. If there is a leak anywhere from the turbo to the intake of the engine, it will cause the engine to get less boost, which means less air into the cylinders, which means black smoke. Check all of the connectors/tubing coming from the turbo to the intercooler, and from the intercooler to the intake manifold and see if there are any problems. The more costly problems which results in boost going down, and black smoke, deals with a problem with the wastegate on the turbo (controls how much boost is produced, and when too much is being made, it will bleed off excess pressure). So if your wastegate is malfunctioning, your boost will go down and you will get black smoke cause the engine is not getting enough air. also, around 160km...80mi, the injectors "can" start to go on the 6.0L diesels....I would check the turbo for leaks, the tubing for leaks, and the intercooler for leaks (a big rock can punch a hole in radiators and intercoolers...intercooler will be in front of the radiator). I hope this helps

Its a dpf not a cat.Easy way to clean out[regenerate]First bring the engine to normal temp bring up the rpm to 4000 for 2 mins,then allow to idle for 30 seconds then bring the rpm up to 3000 rpm for 3 mins and yourfilter will have regenerated [fancy word for clean itself out. DPF = diesel particulate filter.Its important to use good quality low ash oil for your oil changes.

Hi
Firstly these cars have a lot of issues with electrics, not bad but they dont like the wet.

1.If you have got either the air mass sensor or air mass meter Wet then they will not function correctly, you can somtimes clean these and they will work again.

2. The EGR Valve thats " Exhaust Gas Recycle'r" valve this re-uses the unburnt fuel and forces it back into the engine to burn again. modern cars depend on this with all the new emmissions laws, when these go you would be lucky to get 50mph and it would really struggle on hills, this fault can come and go, but normally you will get a yellow engine light, "although not always" again you may be able to clean this, worth a try.

3. the turbo could be at fault, but you can normally still drive the car fairly well. and it's quite obvious with a turbo when they go.

How much do you know about cars? if you know a little then checking these things is quite simple, let me know if you need more help.

Im fairly sure it is one of the above faults but really it is always better if I could see the car, hope this is helpful

Regards

Dan

p.s if you do go to hte garage mention the above parts!

Engine oil over filled or turbo passing oil.

I don't know much about Subaru but I expect the turbo wastegate is controlled by vacuum which is switched by the engine management system.

In the old days the turbo wastegate was normally closed and the manifold pressure was fed into a servo which opened the gate at the predetermined pressure.

The new way of doing things is to have the wastegate normally open and the turbo producing no pressure until the engine management decides the time is right and it switches a vacuum supply to a vacuum servo which then closes the wastegate. With this system the wastegate is constantly moving and so is unlikely to give trouble though the vacuum servo sometimes leaks and vacuum lines give trouble.

A fellow I know had a similar problem where the engine check light would light up and he would lose performance. In theory this was because of an overboost condition but the repair shop after fiddling around with it for a week fitted a new EGR valve to produce a cure.

Send me your car chaisses number to get the wiring diagrem for helping

replace the wastegate vacum lines or wastegate acuator. if they leak it raises the boost. Let me know if its not that.