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Matt, Mechanical Engineer
Category: Mercedes
Satisfied Customers: 22930
Experience:  BEng hons Mech engineering, in auto industry 22 years
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my 2006 c220 cdi, with 36k, was damaged substantially to the

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my 2006 c220 cdi, with 36k, was damaged substantially to the f/o/s and then left in my shed for 3 - 4 years in bits. I have rebuilt it using a lot of used parts, had the turbo rebuilt etc.
Once back on the road I have not been able to cure intermittent running probs. The auto elecs spent £400 trying to get it going properly, and then, after being told it needed the Merc star diagnostics, I then spent £1400 with them, but the car is still not right. Its worse when cold, it doesn't react to the throttle well. Slow to gain speed then growls (pinks) and then chucks out a dark cloud of smoke. When it clears and gets going its not to bad, but there is only the first half of the throttle that reacts. I've had the EGR tested/cleaned 3 or 4 times, changed the MAF, had the turbo nozzle adjusted and actuator tested, but I'm left with low boost pressure, and the Merc dealer says it must be the ECU

This could be a lack of fuel pressure from the electrical pump at the tank.

If the connections to this are corroded or damaged then the pump could stop at any time or could not be running at full speed. Check that its relay switches in and out and the relay contacts are clean and bright – replace the relay if in any doubt and do the same for the fuse,
Ideally measure the pressure at the inlet to the main engine fuel pump and if this is low check the pump as described and also consider changing the fuel filter as if this partially blocked this too will reduce pressure.

If both of these are OK then also check the connections to the EGR valve, if either the vacuum pipe of electrical connection are damaged / corroded then the EGR can be on all time which certainly will hurt performance. Its also possible that its a fault with the EGR valve so its worth removing the valve and cleaning it out with brake cleaner, if it looks particularly clogged then replace it.

If this is OK then check the small vacuum lines to the turbo and its connected control solenoid on the bulkhead, any cracks or leaks can give turbo issues and its best to have the boost pressure measured actually measured with a boost gauge to check that the turbo is healthy and that the sensor is reading correctly

If its a variable vane turbo (they’ll be an actuator on the turbo body - but not a wastegate) then check its vacuum pipework as above and check the connections to the diaphragm / solenoid valve

Also worth checking that the glow-plug relay is switching off as they can stick on and leave the glow plugs also on - on some cars this can force it into limp home

Also worth considering adding a bottle of injector cleaner into the tank as a clogged injector nozzle will reduce power and give poor combustion - the next stage on from this is to remove all the injectors and have them ultrasonically cleaned and flow checked

Also check all the high pressure hoses post turbo/s for any split hoses or cracked metal pipes, also check the ends of the intercooler as its not unheard of to pop the end caps off under high boost.

If the above are all OK then try checking for airleaks after the airflow meter, any air dragged in here isn't 'seen' by the ECU and so not compensated for and leans the engine out causing rough running. As its a mechanical fault it tends not to turn on the fault light and you can sometime hear a 'hissing' noise with the engine running.

Check the hose clips for tightness and inspect the trunking for any cracks or splits and also all the vacuum system, the small bore pipes and fittings for cracks and missing parts.
Customer: replied 3 years ago.

Hi, The Mercedes dealer tested the fuel pressure at the inlet rail, and replaced the submersible pump in the tank, and whilst recently a new fuel filter was fitted, it was replaced again.

The erg valve isn't vacuum operated and has been cleaned and tested 3 times.

The turbo isn't vacuum operated, only by actuator and nozzle.

When the car was first dismantled 3/4 years ago, it was sent to a specialist reconditioner who changed the compression chamber - damaged in the accident, fitted new bearings/seals, and dyno balanced it. When the scanner picked up high and low boost pressure it was sent back to the turbo co. who now say the nozzle was set to high, so they adjusted it, tested the actuator again - ok, and we refitted it. The high boost is now rectified, but the low still exists. An intercooler pipe has been replaced and the intercooler rinsed just in case of a blockage - ok.

Also the MAF meter has been replaced just in case, without effect.

I see that the glow plug light has started to appear pre start, where previously unseen, and the car has improved.

The fuel has had a good dose of dipotane without effect, and the injectors are given as good by the star diagnostics.

Until recently and esp. when cold the car would lack power, make a whooshing noise, then 'pink' and emit a cloud of noticeable smoke, before clearing, but this has now improved. The dealer tried the engine with the exhaust disconnected without success and says he believes the cat and dpf are ok.

The main indicators I experience are - significantly worse when cold, and secondly at no point has the second half of the throttle been effective so the car often struggles when under load (on hills), but the recent resumption of a glow plug light has improved the drivability at present.

Having now spent nearly £2K trying to resolve this issue I'm reticent to spend more without a strong indicator. The management light is still on caused by low boost fault code, although it hasn't been cleared this week

Hello Malcolm

Ok thanks for the extra information

I'd say its worth checking the state of the turbo inlet bypass / dump valve as I've known these to have issues with split diaphragms and weak springs

if faulty you'd lose all your boost as it'd just re-circulate
Matt, Mechanical Engineer
Category: Mercedes
Satisfied Customers: 22930
Experience: BEng hons Mech engineering, in auto industry 22 years
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Customer: replied 3 years ago.

I don't believe it has one, just the turbo with a plate bolted to the lower end which holds the actuator with a rod that connects to the nozzle

Hello Malcolm

in that case it must be an issue with the turbo guide vanes or the variable inlet flaps

as you've had the nozzle / guide vanes adjsuted already I'd check over the actuator and vacuum lines to the inlet flaps
Customer: replied 3 years ago.

The turbo and actuator were tested a flow adjusted only 3 weeks ago

Hello Malcolm

I'm going to opt out here and ask other experts to get involved

good luck
Customer: replied 3 years ago.
If the car has inlet manifold flaps, the Internet suggests the spindle may be stuck or partially seized. I'll ask at the dealers tomorrow
It seems the professional has left this conversation. This happens occasionally, and it's usually because the professional thinks that someone else might be a better match for your question. I've been working hard to find a new professional to assist you right away, but sometimes finding the right professional can take a little longer than expected.
I wonder whether you're OK with continuing to wait for an answer. If you are, please let me know and I will continue my search. If not, feel free to let me know and I will cancel this question for you.
Thank you,
Customer: replied 3 years ago.

I would be pleased to wait a short while

Were there any engine repairs done after the accident?
What were the damages to the power unit?
It would help if you let me know which fault codes were detected by MB Star Diagnosis.

Customer: replied 3 years ago.


When the car had all the repairs to the front offside completed (the impact was in the air box area and was hard enough to need a car bench to slightly realign the f/o/s strut mounting and straighten the inner wing forward of this) The impact pushed into the turbo compression chamber, and the unit was sent to Turbo Charger Services, Huddersfield who straightened the impeller shaft, replaced bearings/seals and dyno balanced it. Everything else in this area was replaced. As the car had been dismantled there were a number of fault codes, most of which were cleared, but initially we were left with high and low boost. Following a visit to MB dealer the turbo was removed and sent back to specialist who adjusted the flow rate at the nozzle, and since which has now left us with low boost only, and the issues as previously mentioned. Today the car had a bad issue - when restarting after being left for 2 or 3 hours. I drove away with little progress and it smoked badly, rattled and made an even louder whooshing sound, but eventually once stopped at a junction cleared and pulled away ok, without the sound rattling or smoke. The other issue is mostly there is now lower half of the throttle resting at all. I spoke to the MB tech yesterday as I was hoping the car had inlet flaps on a spindle which might have been sticking due to a build up but he says this car doesn't have that type of set up - bugger! He did notice that the outlet pipe from the intercooler and the charge tube to the turbo were not fully seated (probably due to the excessive high boost until adjusted) so I need to attend to this. The fuel consumption is deteriorating day on day, I'm now down to around 20 mpg. I will get the codes if needed.

Customer: replied 3 years ago.

Do you need the fault codes before responding?

Turbos with variable vane mechanisms are very difficult to restore. I would suggest to install charger from working car. It is the only way to check if the charger was properly restored.
Active codes would help a lot.
Customer: replied 3 years ago.

The codes are concerning charge boost pressure

2632-008 and


The high boost has now been rectified by adjusting the nozzle to where it should be? I am awaiting reply from Turbo Charger Services, Huddersfield who carried out the initial repair and recent nozzle adjustment

If I need another turbo do I go for a used one or a recon. either way there is little chance of knowing how good they are, and its a days work to change it.

These codes point to jamming actuator of vane control mechanism on the turbo.
My experience so far that turbochargers with vane mechanism are not repairable or rebuildable. Such problems with vane mechanisms after repairs are not uncommon.
Regards, Stan
Customer: replied 3 years ago.

Turbo repairers agree that the symptoms are in line with vane mechanisms, but are puzzled as they adjusted them and didn't see this problem when flow testing. I will give them the OE number of the turbo and they will build up another, I can't see any alternative. I have insisted they use completely different turbo parts for the next one, we don't want to use an unknown defective casting or other usual rebuildable part.

Maybe the rebuilders can provide to you a used and tested turbo from vehicle that does not have such fault codes. Once you confitm to them that no faults related to overcharging are present- they can find the differences comparing to your turbo. I see this as the only constructive way to to go forward with it. The the variable geometry turbo has a very precise efficiency curve, which might be off a little bit somwhere in between the minimum and maximum efficiencies, which causes such a mismatch to the efficiency map in ECU. Another possibility is to have the ECU chip tuned so that overboosting would be a good thing- your car would have more power.
Customer: replied 3 years ago.

I did some specific road testing today. When the engine is running fine it will not rev past (exactly) 3000 rpm. Stop the car and rev it while stationary and it will rev to its full rpm - 4750, but with smoke etc.

Once pulled away it will revert to the lower rpm, once it has made the loud whooshing sound and cleared its throat. This is a constant when hot.

I don't think any of these rebuild companies have used stock kicking about, they either have rebuilt units, but mostly rebuild yours. I did ask a couple but they declined.

Once I resolve this issue I will have the ecu remapped, but it might exacipate the existing prob?

Usualy, the chip tuners can re-load your standard software within minutes.
Since modified software raises the boost threshhold in ECU- it will rather solve the overboosting codes than cause any additional problems.
Customer: replied 3 years ago.

The turbo company have accessed a replacement turbo, which they have rebuilt and tested, and will supply at cost. It will be a complete unit with actuator so no parts will be reused from the original. When available we will get it fitted and see if matters improve, meanwhile I hear that there is a local company dealing with electronic diagnostics and I will approach a guy I know who may be working there shortly, and see if they are set up to deal with a problem ecu.

I do not believe ECU is the problem. Re-mapping it for more power can delete the fault code without replacing the turbo.
Customer: replied 3 years ago.

The turbo is only costing £150 and a friend is fitting it in his workshop, so I'm willing to pay this to rule out or in the turbo.

I have twice contacted a remapping dealer who hasn't replied again. They use Quantum Tuning software, and I have recently been given 2 others - torquetothedevil and emerald. So I will give it another go and see what they say. Thank you for your ongoing advice

Will be happy to assist you further whenever is necessary. Let me know how it turns out
Customer: replied 3 years ago.

I,m following your suggested course, we have cleared the fault codes since the air mass meter was changed and we now have 2025 and 2359, the latter being the ever present low boost pressure.

We have a completely rebuilt turbo ready to fit, but I have now spoken to a remapping agent who are also general repairers. So before we change the turbo I'll follow this path.

They seem confident that they can resolve these issues.

I'll let you know

Ok, sounds good.
best regards,
Customer: replied 3 years ago.

Car is still at remapping garage, who haven't had to much time yet to fully investigate, but currently say it looks like a lack of air, and might be inlet manifold issues. Should hear more soon. Will let you know

Customer: replied 3 years ago.
I hope they will sort it soon, currently still waiting
Customer: replied 3 years ago.

Hi, After 3 weeks the current garage can't find the prob, but they are sure its a mechanical prob not electronic, so to rule out it being the turbo, they are fitting a completely different rebuilt turbo I have supplied. Fingers crossed

Ok, let me know if i can help.
Customer: replied 3 years ago.

The saga seems to go on and on.

Since they fitted the rebuilt turbo, (just in case), they have checked all the exhaust and remapped the inlet, and are now having the injectors tested. Will I ever get the darn thing back, and at what cost, I don't know

Sorry to hear about this.
What fault codes were present after turbo replacement?
Customer: replied 3 years ago.
I'll ask
That would be great,
the more info i could get on the diagnosis steps, the better (fault code numbers, actual and measured values related to the fault codes and symptoms).
Customer: replied 3 years ago.

The reply this morning is "we are at Bosch (injectors) now going through readings. The only fault presenting is a low reading on the MAF but no fault codes stored, will report back when have some news"

If there are no fault codes, it is possible that the symptoms have also disappeared with replacement turbo.

Customer: replied 3 years ago.
I don't think they would be testing the injectors if the turbo change had cured the problem, I,ll wait till the end of the week to see if there is progress
Customer: replied 3 years ago.

I am being asked if the turbo actuator was adjusted to suit the turbo, so I assume the injectors are ok.

The rebuilt turbo which has now been fitted (as supplied by me) has no parts from the cars original. Docs supplied by Turbo Charger Services to show vibration sorting rig results = passed and a flow test showing temp and pressure, all of which passed. Does this mean the actuator has been coded/adjusted to suit the turbo. If not is it only the MB star diagnostics which can then carry out this task? because the turbo was removed and another actuator fitted when the car was with my MB dealer some time ago, and he showed me him operating the actuator via their system to show it was operating ok.

Only turbo rebuilders can adjust the actuator. The turbo must flow very specific values at each actuator position, which must be matched to the map in the ECU. That what makes the turbo rebuilding so complex for this car.
Dealer can only move the actuator to see if it jams.

We come in circle to find that nobody can be sure if turbo was properly rebuilt to suit expectations of the car's ECU.
I personally suggest to have the ECU remapped not tothrow overboost or insufficient boost errors.
Customer: replied 3 years ago.

Hi Stan

After all these months and several turbo tests/rebuilds it has been proven by the turbo charger company that they did not set up the parameters properly. They acquired new equipment and the problem is resolved.

I have informed them that I will be making a significant claim for their ineptitude. The remapping did not per sa resolve but confirmed a good ecu and the subsequent definitive problem.

Many thanks for your protracted efforts

Glad that the problem got finally sorted out.

I am a bit surprised that re-map did not disable the boost fault codes.
Rebuilders should be grateful to you for persisting with the resolution and improving their equipment.

It would be great if you could give a positive rating to one of my answers, since only then i get paid. Unfortunately that will cause an extra charge to you, since you have given a positive rating to previous expert (Matt, he opted out), and got charged for that.

Otherwise you can ask the moderators to close the question, since when you reply- it becomes an open question in my list.

Best regards,