September 9

2009 Mercedes ML320 3 Litre Diesel Engine Oil Cooler Seal Leak

Auto Repair, Mercedes


Mark: Hi, it’s Mark from Top Local, we’re here with Bernie Pawlik, Pawlik Automotive in Vancouver; Vancouver’s best auto service experience. They’re 17 time winners of Best Auto Repair in Vancouver as voted by their customers. How’re you doing Bernie?

Bernie: I’m doing really well.

Mark: So we have a bit of a meaty presentation today, you said, a Mercedes 3 litre diesel with a cooler seal leak; what was going on with this vehicle.

Bernie: Well there was a few things going on with this vehicle but primarily, the first thing the customer brought it in for was a fairly large oil leak at the bottom of the engine and we’ve been servicing this car a while so this leak was there in the past and it’s just getting worse and worse and so basically there’s a large oil leak was the primary concern. It was due for service actually, in fact overdue for service which I’ll talk about later and the check engine light was on.

Mark: So what did you find with the oil leak?

Bernie: The oil leak it was coming from the center of the engine, the valley area so on a V engine there’s two banks of cylinders, one on the left, one on the right and in between it forms a V, the valley sits in the middle and this is where they positioned the engine oil cooler. Oil cooler seal leaks are pretty common on these engines, the actual coolers themselves are pretty much bulletproof unless you destroy your engine but the oil cooler seals do leak so very difficult to actually see the leak on this vehicle because there’s so many parts and pieces in the way, the intake manifold, there’s fuel injection pipes, a lot of, a lot of pieces in the way but the just based on where the oil was leaking from the oil cooler seals were the cause of the leak. So we, yeah we basically stripped down the engine, took the engine manifolds off, accessed the oil cooler and there’s also another area of leakage in that area which is the turbo oil stand which we looked at, at the same time. I’m going to share a few photos

Mercedes Diesel Repair

View of right cylinder head and engine valley, Note the oil leakage. The red arrow points to the oil cooler. The leaking seals are underneath. The yellow arrow points to the intake points that are covered with carbon deposits which restricts airflow into the engine. The green arrow points to the turbostand mounting. There is a lot of oil in this area and likely another source of this engine's oil leakage.

Mark: Sounds like a lot of work to get at the oil cooler.

Bernie: It is a lot of work – here’s a photo, are we seeing this o.k.?

Mark: Yup

Bernie: Perfect, so this is the, this is the valley of the V6 diesel engine with the intake manifolds removed, so a lot of parts and pieces have been removed, many hours of work has gone into what you’re looking at in this photo and there’s a lot of interesting things to see. So I’ve got the coloured arrows here, the red arrow points to the engine oil cooler, so you can see a lot of oil and filth around this area especially heading towards the right side of the picture which is the back of the engine. The green arrow points to the turbo where the turbo oil, the turbo stand sits, it’s a stand that holds the turbocharger in place and there’s oil flowing in and out of the turbocharger through this particular area. Again that’s a source of leakage and based on the amount of oil around that area that, that was probably leaking some oil as well. So the oil cooler which is the piece the red arrow points to was removed, we changed the seals and we put the cooler back in, of course it’s never enough. The yellow arrow and I’m going to talk about it further on as we get going in this hangout points to the intake manifold ports, you’ll see there’s a rectangular or square port and there’s a round one and what the arrow I’m pointing to in this picture is just that amount of black filthy carbon deposits in those ports. This engine’s gucked up pretty badly. That’s where the air, this is where the air flows into the engine so it needs lots of air flow and it wasn’t getting as much air flow that it should have had so on that note we’ll stop the sharing for the moment, back to where we were.

Mark: So I think you mentioned that there was a check engine light on, did this repair have any relation or did that have any relation to the oil leaks?

Bernie: Well the check engine light wasn’t related to the oil leaks but fortunately for the customer, the check engine light was on for a couple trouble codes for the intake valve, sorry the air intake, actually look at my notes here, the intake port shut off position sensor was the codes and it was for left and right bank and what that is actually we’ll just go right to pictures for this makes, as you say a picture is worth a thousand words. This picture is of one of the intake manifolds and this is the opposite side remember that yellow arrow that pointed to all that black sooty stuff well this is the part that bolts onto there and the red arrow is pointing to the round intake ports and these all have it’s called a butterfly valve that opens and closes. The trouble code that was stored in the engine computer was related to this particular system and again there’s a variety of arrows here so I’ll go through all of them. The red arrows point to the valves that open and close, the yellow arrow points, that’s a linkage rod that connects all three of these pieces together, the purple is the swirl valve motor, this is the motor that actuates the valves when the computer tells it to and the blue arrow points to a sensor, now that sensor, when the computer tells the valves to close or open it goes to a final position and when that position is reached then the computer knows the valves are closed, everything is good but the trouble code is being set because that sensor was not seeing that particular item happen. Now the motor was actually working fine it was moving the valves but what was happening is that there is so much wear in the linkage rods, they’re plastic over the years the rods have worn so much that the valves were all opening and closing at the same rate so you can actually see in the picture if you look on the left side you see the valve is actually partially closed and anyways the linkage was so badly worn now the only replacement for this is to replace the whole intake manifold, as you can guess it’s expensive, off the top of my head I think they’re about around nine hundred dollars apiece and there’s two of them so that kind of gives you an idea what this adds to the bill of the job but after completion it, you know, everything is done and fortunately for the customers there’s no extra labour charge to do this work at the same time as we had to remove it. This is a picture of the new manifold, so you can see how nice and clean and clear everything is, at the top of the picture there’s the swirl valve motor, it’s a bit of a different view of the linkage rods are on the bottom of the picture here and actually this is both manifolds coupled together but you can see how clean the ports are, a lot more air flow so the engine will perform, I mean the engine’s going to perform much better after this, after this particular service is done.

Mercedes Diesel Repair

View of 1 intake manifold: red arrows point to swirl valves: note the carbon deposits on all 6 intake ports; yellow arrow points to swirl valve linkage, on this engine there was severe wear in this linkage; purple arrow points to swirl valve motor; blue arrow points to switch which send computer a signal to indicate whether valve is closed fully. On this engine a code was set due to severe linkage wear and the switch not being 'switched on' when actuated

Mercedes Diesel Repair

New intake manifold - note the clean intake ports which allow a huge increase in airflow into the engine

Mark: So did you find any other issues while you were doing this repair?

Bernie: Well it’s funny that you mention that because yes we did find some other issues. This vehicle came in and it was due, well actually I’ll just show a couple things. So here’s the other issue, this is the turbo oil stand pipe, the oil stand and this as I pointed to in the other picture, you can see where it’s bolted down in the engine, it looked like it was leaking, this is the top where the turbocharger bolts onto the engine and the red arrow points to the engine oil, this is the high pressure oil line that goes through the turbocharger so this is feeding oil into the turbocharger, critical for life in the turbo, the turbo’s spinning at you know at 30 to 40 thousand rpms at times, maybe even faster, it really needs good clean oil. If you look in there it looks pretty gucked up, that’s a small hole, it’s only about maybe a quarter inch in diameter at the most but it’s, this oil hole is so badly plugged it’s surprising that a trickle of oil is getting through. The turbo is working, I think the owner of this vehicle is extremely lucky that he had this service done when he did because the turbo would have seized up in pretty short order and just so you know, the hole on the right hand side which is quite a bit larger that is the oil drain back hole so the oil drains back into the engine down through that hole but again this is you know bad maintenance and the other issue this is what was going on the dash of this vehicle; Service A exceeded by 11,415 kilometers. So this light has been on for a very, very, very long time and this isn’t the first post I’ve talked about people who left their oil and haven’t changed it and you know it’s there in black and white, Mercedes doesn’t make it much easier to be reminded you need to change your oil, it’s there every day and every kilometer you go it tells you you’ve gone too far and really if you follow that religiously you’re going to have a lot less problems, I just can’t say it enough, it doesn’t make any sense, you’re saving absolutely nothing by leaving it longer, so get your oil changed, that’s the key message for this and a lot of that, that guck we’ve seen in the intake system may be prevented, certainly the turbocharger failures we’ve talked about them on previous blogs posts, complete engine repairs, there’s a lot that goes wrong with these so, change your oil, change your oil, get the service done regularly.

Mercedes Diesel Repair

Instrument panel display indicating that service is far overdue: If you own a vehicle with these reminders PLEASE HEED THE WARNING: failure to do so will cost you lots of money

Mercedes Diesel Repair

Turbocharger stand: red arrow points to the almost solidly plugged oil supply port. Had this plugged fully the turbocharger would have quickly seized.

Mark: So it seems to be pretty like we’ve seen a few of these now and this has been a pretty consistent issue, these diesel motors from Mercedes or maybe any diesel motor really must be pretty regular, you’ve got to be rigorous about getting the oil changed on time, you can’t stretch it very far even if it’s a synthetic.

Bernie: Absolutely and this uses synthetic oil and the oil change intervals in these I believe is about 15,000 kilometers, that’s a good amount of time you know for, you know if you drive a lot, huge distances I mean that’s a couple times a year but if you’re not a huge driver it’s only probably once a year service, it’s not a lot so you know it is a couple hundred dollars but it’s only one service a year, maybe two but the cost of course you know, the bills for these kind of jobs are enormous when you leave it too long especially if you wreak the engine. We had one that was over 20,000 dollars so yeah, it’s important to do the service, I mean on any engine it’s important, gas running engines too, I mean it’s more critical now than it ever has been.

Mark: So would you say that with all that corrosion that was in those intake ports and everything I’m sure that part of that was just due to how diesels, how diesel fuel is burned but is that more a function of you know would a regular oil change have helped with that or is that more of a function of they needed to have an engine flush or you know maybe some of the other services that you guys offer the, I’m trying to think the fuel injector cleaner

Bernie: Cleaning services of diesels that can help with that, there are also EGR cleaning services that we can do, I mean a lot of it is a function of the design of the engine most all modern diesel have an EGR system exhaust gas recirculation that it’s a critical emission component to remove NOx emissions which are really high in the diesel because of the combustion temperature and pressures so it’s an important emission item but it also leads to this grungy debris if you had no EGR system that none of that debris would be there, it doesn’t seem to be too much of an issue with American diesels for some reason like the trucks and I don’t know if it’s because they’re larger, bigger breathing engines but we see it on TDI Volkswagens we see it a lot on the Jeep Liberty, it’s a small Italian 4 cylinder diesel, we see it on the Mercedes but changing the oil and doing regular service it’s critical to minimizing that and also highway driving, again it’s another thing a lot of these diesels people just use them around the city and that’s, that’s definitely harder on the system as well because the engine doesn’t get hot, warm enough, we’ve talked about this in the past, driving it and getting it good and hot that’s the best for diesel, highway drives much better. Incidentally I do want to mention this, this vehicle has 273,000 kilometers on it, so it’s had some pretty good usage and good life and that’s that is a good thing and after the work we’ve done on it, I mean it will be good for a quite a lot longer timeframe so even though the oil change is, was way overdue you know, definitely a bad thing and all the things that were plugged and blocked, cleaning all that out will get a lot more life out of this engine so as long as the owner keeps changing his oil in a regular timeframe I don’t see why he can’t get 500,000 or a million kilometers out of one of these engines, I mean they are very good.

Mark: So there you go, if you need maintenance or repairs on your ML320’s 3 litre diesel or any Mercedes, Jeep, VW diesel, these are the guys to see in Vancouver, Pawlik Automotive, they’re experts in this stuff, give them a call 604-327-7112 to book your appointment or check out their website, tons of good information on there, Thanks Bernie.

Bernie: Thanks Mark, talk to you again soon.

About the author 

Bernie Pawlik

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