Unfixable intake air leak.

[Don212]

Hi All

I have a high mileage,460k, w212 e250cdi that i use for a chauffeur service in Australia.

A few months ago driving home ,felt a lil bump with lose of power eml and soft limp mode, could drive home but had to manually change gears.

Previously had the boost hose split with exact same symtoms and so thought it was that and could restart car and not load it enough to trigger limp mode.

That didnt work so took it to mech ,scanned it and returned maf code and gearbox code.

Cleaned maf, no result, changed maf, not oem but vemio, no result.

Ill cut the story short and say that we're basically throwing darts, replaced maf, other intake sensor, egr valve/cooler, 2 intercooler hoses, intake manifold and this week pcv cover.

Car idles fine with no noticeable different sounds.

If the pcv doesnt solve the problem we're both at a lose as to what could be causing this air leak, new maf was recalibrated, so if anyone has any idea or a similar solved scenario i would greatly appreciate the suggestions.

Cheers

 

[toteimerced]

I would have suspected the boost hoses, but you have changed them, do a smoke test to see if there are any leaks.

 

[Don212]

I would have suspected the boost hoses, but you have changed them, do a smoke test to see if there are any leaks.

Done that, nothing to be seen, have replaced all known common parts that could cause error code, pcv ongoing atm, but are there any uncommon parts/ scenarios that could cause the air leak? (P227906)

 

[Don212]

P.s all replacement parts are reputable aftermarket brands

 

[MrGreedy]

On such a high miler, and somewhere warm, other than the boost system, my immediate thought went to something EGR/intake manifold burned through.

But if you've done a smoke test and there is zero smoke escaping, I can only assume it's not a boost leak. So a sensor is the logical option.
Have you looked at the DPF pressure sensor and lines? It's a cheap enough part that might be worth replacing if you haven't.

On my E350, it was giving issues but not throwing consistent codes. I don't know the similarities between the two engine systems I'm afraid.

 

[Don212]

On such a high miler, and somewhere warm, other than the boost system, my immediate thought went to something EGR/intake manifold burned through.

But if you've done a smoke test and there is zero smoke escaping, I can only assume it's not a boost leak. So a sensor is the logical option.
Have you looked at the DPF pressure sensor and lines? It's a cheap enough part that might be worth replacing if you haven't.

On my E350, it was giving issues but not throwing consistent codes. I don't know the similarities between the two engine systems I'm afraid.

Have replaced egr and intake manifold to ne effect, currently replacing pcv but will look into dpf sensor.

 

[MrGreedy]

Have replaced egr and intake manifold to ne effect, currently replacing pcv but will look into dpf sensor.

Everyone says buy genuine for these on the E350. But they are made by Bosch. If going Bosch for around £30, try to get one from a proper distributor like a bosch diesel center so you are pretty much guaranteed it's new and genuine.

I know yours is the 250, but I only have 350 experience

 

[Roku]

Hi, I have exactly the same issue here. I’ve also replaced all the parts u mentioned, and no intake leak has been found when tested with smoke and pressure. The car is a W204 OM651 220CDI. Mileage 220k. Also dpf regenerated and after regeneration, the DPF fill level is 15%, but after driving 100 km, it goes up to 55%. The pressure difference at full throttle is a maximum of 270 mbar. The issue isn’t constant; it only appears intermittently. The injectors are currently removed, and on the test bench, they’re showing similar values. any hints?

 

[Roku]

Additionally, the turbo pressure sensor and intake manifold pressure sensor have also been replaced. At idle, the target boost pressure is 1.25 bar, but the actual pressure is around 1 bar according to both sensors. However, at steady throttle while driving at 2000 rpm, the target boost pressure and intake manifold pressure are aligned, but the turbo pressure sensor reads are 0.3-0.4 bar lower. No vacuum line leaks. Is that normal reading?

 

[Don212]

Hi, I have exactly the same issue here. I’ve also replaced all the parts u mentioned, and no intake leak has been found when tested with smoke and pressure. The car is a W204 OM651 220CDI. Mileage 220k. Also dpf regenerated and after regeneration, the DPF fill level is 15%, but after driving 100 km, it goes up to 55%. The pressure difference at full throttle is a maximum of 270 mbar. The issue isn’t constant; it only appears intermittently. The injectors are currently removed, and on the test bench, they’re showing similar values. any hints?

Not fixed yet, mech thinking that manifold seals may have been incorrectly installed.
Apart from that, no idea on a permanant fix.

 

[Don212]

Still no fix ,mech called and said they rechecked seals around new manifold which were fine as well.as the turbo seals.

He mentioned there was a large crack on top of air filter box which will be replaced with a second hand unit.

As well will replace the drivers side charge pipe.

Apart from that we are at a lose as to what it could be as most componants have been replaced and when driving all data is within normal ranges.

 

[Don212]

Quick update,
Mech rang and is 95% sure that the turbos are the cause for the air leak!!
from what i could understand at the time as the mech was quite excited so don't quote me, but they smoke tested the actual turbo and said there was smoke leaking into the engine when technically it shouldn't.
Sorry bout the sh1te description, but the mech also mentioned he has never seen this "scenario" before but is going to video the problem,symtoms and the solution and i will upload hopefully end of next week.
Cheers

 

[MrGreedy]

Finger's crossed this is it.
I couldn't work out how their was a leak, but smoke test showed no external leak.

 

[Mickyh7]

Just seen this.
One of the most 'Copied' O.E. parts for sale online are Bosch.
They are always priced ridiculously cheaper than motor factors.
The parameters are miles away from originals, so they rarely work or fix faults.
But people believe, because they have bought a new, branded part, they are not at fault.
Sensors or Meters, always buy from a reputable seller!
Buy cheap, buy twice.
Ask me how I learnt this!