Dynamic

I'm experiencing exhaust smoke coming from under the hood on my 2007 GL320 CDI. In only happens sporadically and each time it happens by the time I pull over to safe place to pop the hood open it goes away. Sometimes it's just very little smoke and sometimes it gets to the point that inside the cab fills up with smoke to the point that I need to crank all the windows open to vent it out. I noticed that it happens more in cold weather then warm and I also experienced same symptoms on my 2003 Sprinter which has the 2.7L engine not the 3.0 as the GL does yet with the sprinter it only happened twice in the last two years.

I mentioned the problem to my mechanic but he said that it will be difficult to find unless he can experience it happening but since this is something that happens once a week on average it is difficult for him to find.

I'm trying to figure out the route the exhaust passes through before it is out in the exhaust pipe and what possible parts could fail that would let the exhaust out under the hood.

Shadow5501

I've had the flex pipe crack on an om642, albeit in a different chassis. There is a short flex pipe bolted to the back of the turbo to make the 90 degree turn downward and couple to the remainder of the exhaust system. There was never any visible smoke under the hood, but the cabin would smell of diesel exhaust when at a standstill. There was some evidence of soot in the area around the crack. The symptoms don't exactly match what you are describing, but it's something worth checking.

alx

There is always a small amount of exhaust smell circulating under the hood. Especially on higher mileage diesels. You will get it injected in the cabin if your hvac air intake (pass side hood vent) is blocked with ice / snow in which case the hvac sucks air from under the hood.

However if you get actual diesel smoke in the cabin I would check header bolts as well as turbo flex pipe in the back.

Dynamic

No snow, the car is garaged and never covered with snow. I doubt it is anything such as the turbo flex pipe or loose header bolts since that would have continuous smoke and not occasionally like a on / off switch and I'm talking about a massive smoke cloud when this happens people that are standing next to me on a stop light point at the hood as if my engine is on fire.

alx

So much smoke will leave sooth at its place of origin. Find it. A box of q-tips does wonders

DennisG01

Just a thought, but are you positive that it's exhaust smoke and not an oil leak? If there was oil leaking out, and landing on a hot surface, couldn't that cause a sudden burst of smoke? I would think that an oil leak would be consistent, but who knows... maybe the temperature (expansion/contraction of items) has something to do with it.

Dynamic

Oil smoke has a different smell. This smells like exhaust smoke but stronger since it doesn't go through the charcoal filter in the exhaust. Does anyone have a diagram of how the exhaust travels. Between when it travels out the exhaust valves till it goes out the exhaust pipe. Could it be the EGR or something in between?

DennisG01

It's pretty straight forward... starting at both ends of the exhaust manifolds, then you go the turbine, then the downpipe and the rest of the exhaust tubing/components. As Alx mentioned, look for the telltale soot. Another possibility could be leaking fuel - same idea as the leaking oil. I would think it has to be something up at the engine, though, for you to smell it that much while the car is moving.

Bimmer777

I had an exhaust leak problem last fall. Turned out to be the gasken on the angled EGR pipe. The actual problem was one of the bolts that holts the pipe backing out. Here is the thread on it.

https://mbworld.org/forums/gl-class-...eak-gl320.html

Lamont Clemons

what did you come up with

lkchris

Well, we know that motor oil in diesels turns black really quickly due to fuel blow by so not so sure an oil leak that encounters hot manifolds wouldn’t smell a lot like diesel exhaust.

Anyway on mine one time when some repair was performed, the dealer mechanic misinstalled a gasket in the EGR system and I had fumes in the cockpit. Maybe a possibility, then.