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MB Paul
MB Paul, Mercedes Technician
Category: Mercedes
Satisfied Customers: 4317
Experience:  Mercedes Benz Qualified Diagnostic Technician
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My ml mercedes 270 when warm,10 mins.loss of power.cant go

Customer Question

My ml mercedes 270 when warm,10 mins.loss of power.cant go above 3000 revs
Submitted: 2 years ago.
Category: Mercedes
Expert:  MB Paul replied 2 years ago.

Hi,

This could be down to many things & a diagnostic check for fault codes should be the first step but here are some common issues that you can check:

Check the intake hoses from the turbo to the intercooler & the intercooler to the intake manifold - these are prone to splitting & only open up when under boost pressure from the turbo, so check carefully!

Also check the intercooler itself for signs of leakage.

Check the intake manifold - there are inlet ports that can leak, these can be difficult to see as they are located on the underside of the manifold close to the engine block. Large oil leaks from under the manifold are a sign that this is leaking.

The catalytic converters are prone to blocking & can sound like an air leak at times due to the pressure build up in the system from the turbo - inspect around the cat joints for signs of soot being forced out, another tell tale sign of this problem.

EGR can cause problems also if blocked so a check of the EGR system is advisable.

Sensor readings should be checked on a diagnostic tool such as Mercedes STAR diagnosis - the MAF (air mass) sensor can be a particular problem.

All of the above can cause the engine to go into limp mode which shuts the turbo down - the turbo itself can also cause problems but all of the above should be eliminated first.

Best regards, Paul

Customer: replied 2 years ago.

Had diagnostic done.2 weeks ago.nothing came up

chap said my waste gates not opening.he took hose off while car was running.he said turbo needs replacing.but your answer.yes I have oil spots again.i put some smoke repellant in to tank with diesel 5 wksago.since then this happened.also had a full sevice done.bit reluctant to change turbo yet, because it works cold.sprayed mass censor with elec contact.is cat blocked and blew seals.

what to do next.gavin.what u think

Expert:  MB Paul replied 2 years ago.
Hi Gavin,

I would be surprised if there was no codes stored - was it checked on Mercedes STAR diagnostic tool? Many cheaper tools will not read all codes correctly so I would suggest having a check done on STAR if this has not been done.

With regards ***** ***** the MAF this is not really a reliable way of eliminating it if faulty (& in many cases can actually make it worse in my experience!) - the readings should be checked on STAR to make sure it is actually reading ok - there is a guided test that checks this reading is correct.

The turbo will not actuate if there are other faults as mentioned as the ECU will shut it off to prevent damage.

Have you actually had the intake pressure tested & physically removed the cats to inspect for blockage?

Best regards, Paul
Customer: replied 2 years ago.

Yes star was done.he said its merchanical.since my bas /asp light s on.i ll have to let mercedes do a star test on it.but I do have oil leak spots now.i changed intercooler.damp patch ln bottom left corner.no differant.Hoses look fine .but underneath not sure.but intercooler is ok now.

Expert:  MB Paul replied 2 years ago.
Hi,

Well all of the above will need to be checked out in turn to make sure each component is good.

The above list is usually the cause of limp mode in almost all CDI engine vehicles!

Best regards, Paul
MB Paul, Mercedes Technician
Category: Mercedes
Satisfied Customers: 4317
Experience: Mercedes Benz Qualified Diagnostic Technician
MB Paul and other Mercedes Specialists are ready to help you
Customer: replied 2 years ago.

Are you a mobile mechanic.were are you based.gavin.can you do it

Expert:  MB Paul replied 2 years ago.
Hi Gavin,

Not sure if you saw my last reply on the other question you posted but I am in Kent SE England in a dealer - not mobile Im afraid!

Best regards, Paul
Customer: replied 2 years ago.

Ok thanks paul.

Expert:  MB Paul replied 2 years ago.
No problem,

good luck with your repairs & let me know if you need anything else.

Best regards, Paul

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