ML 270 CDI unknown hose query - leaking fuel

[Andy McMullan]

Hi Everyone.

I bought my 2001 ML 270 recently and it has a few issues.

The MOT flagged up a diesel leak. I'm getting some drops on the ground around the nearside rear of the engine.

It only seems to drip out after the engine has been run for a while and is up to temperature.

I think the diesel is either coming out of a hose at the rear nearside of the engine or running down the hose. There was as a tiny drop of diesel on the end of the hose when I checked earlier after the car has been sitting for a day..

I'm going to take it for a good run later and see if it leaks some more.

Could someone identify this hose please? I've had a look at the fuel system schematic and can't see it listed.

In my introduction post another member mentioned that the fuel system was closed and this wouldn't likely be an overflow. I cant see any diesel leaking out of the injector return pipes and all the fuel hoses are dry.

The hose can be seen in the attached photo beside the yellow label. It looks like it's not supposed to be connected to anything, so if someone could confirm that would be great. I pulled it out a bit for the photo.

Cheers, Andy

 

[mersum1es]

Have you checked no moisture on foot of the injectors? That hose *could be* coming from overflow hole behind of the engine, hole is drain of the engine head block top (where injectors sit).

 

[Taffy7hfa]

Good advice from mersum1es above, I would also check the swirlflap spindles for leaks, there is one sat right above the pipe in your photo, you will find it much easier to access the whole area if you remove the wheel arch liner, although it looks as though you may have done that already

 

[Andy McMullan]

Have you checked no moisture on foot of the injectors? That hose *could be* coming from overflow hole behind of the engine, hole is drain of the engine head block top (where injectors sit).

Thanks.

 

[Andy McMullan]

Thanks for the feedback guys.

I drove the car a bit and accumulated a significant amount of diesel in a clear tube I had rigged up over the hose. (First photo).

The hose does plug into the overflow hole where the injectors sit and on inspection, the recesses where the injectors bolt down into, have pools of diesel. This is where the cotton buds are sitting in the photo.

The top leak off pipes seem intact so it looks like the diesel could be leaking lower down the injector set up?

Someone has fixed the black death before. The guy I bought it off said he got the injectors 'cleaned' and there is residue of the black tar in places.

Maybe the fuel wasn't connected back up properly during this repair or seals have perished and need replaced? Could the injector feed pipes just need tightened?

Could I get some info on what I should replace please?

Is there a website that has parts diagrams part numbers?

Thanks again for the help so far. Really chuffed to have found the leak. Fingers crossed its a straightforward repair.

Cheers.

 

[mersum1es]

You have to clean and dry everything, and then after start the car, inspect carefully where diesel starts to accumulate...

Possible leak sources are high pressure fitting, bottom of injector electric part (rare), cracked nozzle holder cup (and of course tank line fitting but that you have ruled out).

Now when injector have been out and 'cleaned', it is possible that something has been left loose (thumb rule ;over 80% of faults are due to previous maintenance... )

 

[Andy McMullan]

I blew all the diesel away with an air line and after a short test drive I could see diesel pooling around the base of the first injector. I wrapped some pieces of cloth around the upper parts of the injector and high pressure inlet pipe and did another drive. None of the cloth showed any signs of diesel so that leads me to believe that the diesel is leaking from the lower part of the injector.

The photo shows the diesel starting to accumulate to the right hand side of the torx bolt. Are there any potential leak points in this region?

After the 2nd drive there was diesel at the other injectors but this may have traveled along with the movement of the car.

Cheers

 

[Blobcat]

Diesel injector leaking is quite common in the ML270 for some reason. Just be very very careful with the injector hold down bolts, lots of people strip the threads. I had a friend who had on injector held in with a heli-coil that failed on the M4, the injector popped out and sprayed diesel over the engine. It went up in flames... It was Mercedes that fitted the heli-coil following an injector replacement.

 

[mersum1es]

I believe it is cracked nozzle holder then... yes, fluids are traveling in 'injector ditch'.

 

[Andy McMullan]

Diesel injector leaking is quite common in the ML270 for some reason. Just be very very careful with the injector hold down bolts, lots of people strip the threads. I had a friend who had on injector held in with a heli-coil that failed on the M4, the injector popped out and sprayed diesel over the engine. It went up in flames... It was Mercedes that fitted the heli-coil following an injector replacement.

Thanks. Should I re-torque the injector hold down bolt?

 

[Andy McMullan]

I believe it is cracked nozzle holder then... yes, fluids are traveling in 'injector ditch'.

Thanks. Can the nozzle holder be repaired or replaced?

 

[Blobcat]

Thanks. Should I re-torque the injector hold down bolt?

I can’t remember if they’re single use, it’s a low torque figure and another 90’ turn. Special bolts are required. There’s quite a few on here that have done it (I’m not one)

 

[mersum1es]

Thanks. Should I re-torque the injector hold down bolt?

Do not! Like Blobcat tried to remember, they are stretch bolts and single use only. If you try retight them, you most like just snap them! Bolts and bottom seals are cheap even from dealer, get couple spare at same time.

Nozzle holders are available on every diesel garage which sell/repair injectors, spare part is universal. But pull old injector out first to be sure it is holder cup (very very rarely there has been crack in injector body too - could have happened if previous owner have had BAD black death and strenght of bigfoot....). Just in case, run engine hot before trying, cracked holder may cause black death too, and injector may be already sticky to remove.

 

[M80]

Re torqueing is definitely a no no. It has to be done right 1st time.

My issue would be that who ever did the black death repair hasn't demonstrated a caring attitude by leaving so much of the tar behind.
I understand that shifting it can be a laborious bitch of a job, especially when it seems that it has been left to fester and cause so much tarring, but still.

I would want to do that injector again, and possibly all others for good measure.

The polishing of the seat and the injector are important to prevent re occurrence. The cleaning of the bolt hole is critical to be sure of correct torqueing on rebuild. I hope there aren't any heli coil type repairs but I would rather know they were dome correctly.

The fuel feed pipes can be over tightened twisting the olive, that could cause leakage. But if I understand you've eliminated that.

 

[Andy McMullan]

I've ordered up a set of bolts and washers and will remove the injector for inspection. I'll update the thread with my progress.

The quick responses are much appreciated.

Cheers, Andy

 

[Andy McMullan]

I've now replaced my injector seals and have diesel still collecting at least around the base of injector 2. This is where it first showed up after starting. I added some UV dye to the diesel and can see some signs of diesel leaking from the union on the injector supply pipe of injector 2 and 3.

The picture shows where the leak is, where the tip of the screw driver is pointing. (injector 1 shown). It looks like a slight leak on 2 and 3, but I'm not sure if this would cause the amount I'm seeing collecting at the injector base. It looks like there is a replacement part for this (nozzle part kit), that screws in to the injector. Is this a common leak point? Would a slight leak here give a fault code?

(The zip-tie on the injector is to help secure the multi plug which has a broken tab.)

Am I possibly on the right track with this? Cheers, Andy

 

[M80]

Is it possible that loosening the diesel supply pipe has loosened the union into the injector?

 

[Andy McMullan]

Good point. I'll have a look at that later.

Cheers, Andy

 

[mioba]

Did you check all those braided rubber inkector pipes they are a service item and will perish over time at the ends, a feel at the end to see of they wet.

sorry to say that's a dirty engine and the PO didn't do a good job, maybe he sold the car as these problems were peeing him off, persevere good chap and you will succeed"

 

[mattkh]

...... the injector popped out and sprayed diesel over the engine. It went up in flames...

Really. After buying my 190Db, I used to recommend diesel engines because diesel does not ignite easily.