I have an 06 ML320 with 200,000km (120,000 mile)

I have had it about a year and gone 26000 km.

I have always had an oil leak which comes out on LHS side of block towards the front but the front face of block (belts etc) is clean and dry. (ie its coming from the rear or the side - it looks like engine oil but the power stearing fuid is low as well so haven't ruled that out - yet)

I just changed the air filters and fuel filters and noticed when I pulled out the plenum that there was oil under the plenum (at the turbo) and also in the inlet of the turbo.


I am not sure if I have an oil separator issue (being that its obviously at the inlet side of turbo) or a turbo seal issue.

I must add that the oil leak is not very major - in 10,000km the oil level is only down 3mm on the dipstick

I am new to the car but have played with a cummins diesel recently. I rebuilt the turbo on on the cummns but that was oil on the exhaust side of turbo - I thought a turbo seal failure on the inlet side would leak more to the inlet manifold/intercooler side as that is the flow of air - unless its a huge oil consumption???

I assume the oil separator is on the rear rhs of the motor (the hose coming into the plenum) as there seemed more oil in that area?

Car generally drives well but sometimes it surges etc on slow crawling speed (say 2nd to 3rd) which I was thinking was a transmission issue as it wasn't constant etc.

Sorry about the long thread, any thoughts would be helpful

When I say LHS or RHS I am meaning when sitting in the car

 

I just thought I would add that I am calling the plenum the "Y" pipe that joins turbo inlet to the air cleaners.

I have been reading on other forums (which I am not a member of) about the air cooler leak on the bluetech - and the orange seal (I assume on the inlet to the turbo)

is that the same on the non bluetech models?

I am not familiar with the bluetech model and differences to the normal ML320 CDI

 

it can be the orange seal on the turbo- which most of us change every oil change

there is a smaller orange seal to the left of that, it can leak also

also the y pipe has been upgraded because the part that tightens down on the big orange seal tends to crack and it leaks there

inspect the y pipe out of the car really well
and change both orange seals

it could also be the oil cooler leak which is a bigger deal- not sure where that leak shows up since i have not had one

pretty sure cdi and bluetech are the same on any oil leak problems

good luck

 

Thanks for that, where does the oil come from? I was assuming the oil separator but if it is normal then that makes me happier.

Is the smaller orange seal on the same pipe? or is it on the pipe to the intercooler?

 

the turbo has oil in it, so anywhere there is a leak it can get out

the smaller seal is i think a heater hose or something... cannot remember but it is to the left and closer to the front of the car from the big orange seal, you will see it

i have changed the oil separators on mine also but because we were concerned they were worn out not because they were leaking

 

The seals on the turbo and oil cooler are notorious for leaking. Need to change from orange to new purple seal. The oil coolers also develop leaks.

 

yes the oil coolers leak too and if that is your problem you need to get the new seals

but i would start with the big and little orange seals up top and check the y pipe for leaks first

hopefully it wont be the oil cooler..

 

These diesels are leak prone.

I agree with clvincent - after replacing the large and small seals just keep an eye under the "Y" pipe to see if it stays dry.

To check the oil cooler seals you may want to drop the bottom engine cover. If it is saturated that might be an indication that the oil cooler seals are failing.

You'll need to make a decision on replacing the oil cooler seals - it's labor intensive and expensive. Had mine replaced at 60,000 miles by a good Mercedes Indy shop for $2,100.

At only 3mm of oil usage in 10,000 KM it's not very much.

 

.


Sorry about late reply - been away for work and no internet.

I actually have had my bottom cover off ( since I bought the car 12 months ago). It was pretty saturated when I bought it.

The oil leak seems to be coming down on the LHS (when driving forward) and towards the front of the block.

Where does the oil cooler leak normally present? If agree that if it is the Oil cooler I would probably live with it.

With the "purple seal" I looked on Pelican Parts and they listed 642 094 00 80 but the colour in the listing is orange - is the "improved" purple one from Mercedes or an alternate supplier.

 

Besides a saturated undercover, mine presented itself with oil coming to the front of the left side of the engine - looking at it from the front.

The purple seal is a Mercedes replacement made of Viton. I do not believe the old orange ones are available anymore as this change took place about two years ago.

 

the turbo seal and little seal are orange
the oil cooler seals i guess are purple- i have not had to do an oil cooler yet


make sure you check the y pipe OUT of the truck, check it good
BOTH of my trucks the y pipe was cracked and had to be replaced, this will leak and look like an oil cooler leak
the new orange seals do you no good if the pipe around them is cracked

dont buy orange seals until you check the y pipe because the new y pipe is different and the seal is different

i dont know any part numbers, sorry

good luck and keep us up to date

 

Thanks heaps for all your help in this

I will definitely pull the Y pipe out and give it a good check ASAP (way work is it will probably be at Christmas)

The oil cooler leak presenting on the LHS is making me think that is the issue - will probably live with it

Does the oil cooler leak escalate - or does it just stay same volume?

 

My understanding is the oil cooler leak will get worse

 

Unfortunately the existing seals will continue to deteriorate.

 

My ml320 cdi is 2008 and it looks like getting a small leaking ( drops a day), I checked the oil level and it almost the same for 3 months.

A shop staff checked it little bi and think it might be the oil cooler(I know it is bad news for my pocket). So I live with it for half a year.

Currently, because of COVID-19, my ML just keeps staying at the garage, And I found it did not leak (no new drops, "THANKS COVID-19"). If I am right, it could be a sign that the leaking is not from the cooler.

I hope anyone can help to explain. Also, help me to find the root cause( I more concerned about the turbo seals).

Thanks.