February 1

2008 Mercedes ML320 – Exhaust Fume Repair

Auto Repair, Mercedes


Mark: Hi, it’s Mark from Top Local Lead Generation and we’re here with Bernie Pawlik of Pawlik Automotive in Vancouver they are 15 time winners of Best Auto Repair in Vancouver as voted by their customers. How’re you doing today Bernie?

Bernie: Really well.

Mark: So we’re going to talk about a Mercedes Benz ML320, it had some exhaust fumes - what was going on there?

Bernie: What was going on, well so our client brought, it’s an ML320, it’s a diesel engine vehicle, a 3L diesel and they were getting diesel exhaust fumes in the cabin of the vehicle. We did some diagnosis and first step was road testing the vehicle to verify that concern and could smell it right away in the car, it was pretty noxious, we could understand why they were concerned about it. So we proceeded to do the diagnosis on the exhaust system and what we found was interesting was it wasn’t actually an exhaust problem at all. The problem was actually a crankcase breather valve at the back, right near the engine, right where the cabin air would be sucked into the engine and it was leaking crankcase blow by gases which are, you know when an engine runs, there is a certain amount of combustion gas that escape past the piston rings, these are called blow by gases. Every engine, any internal combustion engine has to deal with that whether it’ gas or diesel and they have a ventilation system where it sucks the gas back into the engine and re-burns it. The crankcase vent valve was leaking so it was leaking exhaust fumes, even worse than car exhaust, more noxious right by the cabin air filter area. So that’s the first thing we found. We’ll just go to a couple pictures here.

Mark: Are these common problems on this engine?

Bernie: Well, this is the first one we’ve seen but there are a number of issues with the crankcase vent systems on these vehicles. The other issue that we found that was interesting… so here is the engine cover that you would see when you open the hood of the vehicle. Not much to see, the crankcase vent valve is hidden actually, well if you’re looking down at the hood, at the back left corner of the engine and this is what things look like with the cover off. There’s an awful of of bits and pieces, there’s a lot of complexity with this engine as I talked about before, that yellow arrow points to the crankcase vent valve and unfortunately you can’t see it because it’s kind of in that darker corner of the engine compartment but that’s where the vent valve was. Now to get to it and check things out, we had to remove a number of other items where the green arrow points, that points to a fuel injector, sorry that points to the air filter box and underneath that is a nice foam cover, a noise reduction cover and we found something interesting under that cover as well - you were asking about common problems. We found this. This is the centre fuel injector and all that black guck in that area is not normal. That is combustion gas and a bit of diesel fuel that has leaked from a blown injector seal at the bottom of the injector. So this is another thing that we found that is contributing to the smell in the customers vehicle. Is this common? This is the first time we’ve actually seen this particular concern on this vehicle but from what we’ve read it does happen from time to time. This engine is a commonly used engine, it’s in Sprinter vans, it’s in Jeeps, so this is the first time we’ve found it but it is something definitely that happens from time to time.

Mark: Wow, it doesn’t look good.

Bernie: No it isn’t and unfortunately it’s an expensive repair which gets me to the other interesting question about where to buy parts for these engines. So you shop around, because we’re an independent shop we can shop a variety of sources and actually the cheapest place to buy this fuel injector, and is brand new is directly from the Mercedes Benz dealer. Substantially cheaper from any other source we can find and everyone else sells remanufactured fuel injectors which are good but not as good. It’s one advantage that people don’t think about dealing with an independent auto repair shop, a good one that’s conscientious, we’ll shop around for the best price on parts and based on what the best quality and price is, which is an option you don’t get when you go to the dealer, you’re only going to get what they sell, the dealers brand and sometimes they are cheaper but if they’re not then you’re stuck with that anyways.

Mark: So what else did you find?

Bernie: Well, what else we found was interesting. This is a picture of the turbo air inlet duct and I’ll just go back to our original picture, that’s the red arrow, points to where this photo was taken with the duct off. Now there’s a lot of oily guck there and this is another common problem on this 3L Mercedes engine. There are some big rubber seals, the red seal you see on the left, that’s the small seal from the vent valve which we’ll replace when we replace the crankcase vent. But there is also a very large rubber seal where the duct, and I’ll go back to this picture, that sort of Y shaped piece that goes across the engine, there’s a big rubber seal in there as well that leaked. What happens when these leak, and I believe we’ve done a post on these before, the oil leaks down and there’s an expensive valve underneath called a Swirl Valve and if enough oil leaks down it eventually gets into the valve and wrecks the valve. So this is something that you want to fix on one of these 3L Mercedes engines, you want to keep an eye on them, you want to make sure you fix these seals. Another thing that is good about the Mercedes engine is you can buy these rubber seals for a very reasonable price from the Mercedes dealer, whereas with a Jeep they use a different type of air intake duct and you have to buy the complete duct pipe which is substantially more costly. But fixing it is infinitely cheaper than waiting until it leaks and wrecks your swirl valves. So with just one last picture to look at, this is the fuel rail with the new injector in and you can see where that black guck was once has now been cleaned and removed and everything is all good. That is our picture show for today!

Mark: How did the vehicle run after you repaired everything?

Bernie: Oh it was great, ran really well, no more fumes. We also changed the cabin air filters because these filters were right near by the area where these fumes were being sucked in and they do need to be changed on a routine basis. But we figured it was a good time to change them with any extra particles that got in there and they were quite dirty. But yeah, the engine ran great. With that fuel injector leaking as well there was undoubtably some engine performance being lost but these engines have very sensitive management systems so if anything was severe the check engine light would of come on and nothing did. But definitely the vehicle ran great, no more fumes and makes for a happy customer.

Mark: So if you’re looking to be a happy customer with your vehicle and it could have problems even before the check engine light comes on because they are not foolproof, the computers are just computers Give Bernie a call, you can reach him at 604-327-7112 or check out their amazing website pawlikautomotive.com - give them a call. Thanks Bernie

Bernie: Thanks Mark, talk again soon

About the author 

Bernie Pawlik

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