Here's an interesting one for you guys; I've noticed that my roommate's 1991 350SDL with OM603 engine makes a sizzle sound every 3 seconds at idle. It sounds like when a drop of water hits a hot skillet and is coming out of the exhaust.

The engine runs fine, but it's got me intrigued as I wonder what it means. It sounds like "clatta-clatta-hiss, clatta-clatta-hiss, clatta-clatta-hiss."

Logically thinking, it seems that a drop of something (whether it be oil or coolant) is dripping into the exhaust. Does this sound familiar to anyone?

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1967 W110 Universal Wagon, Euro, Turbo Diesel, Tail Fins, 4 Speed Manual Column Shift, A/C
1980 W116 300SD Turbo Diesel, DB479 Walnut Brown, Sunroof, Highly Optioned, 350,000+ Miles

If it's when it's cold, it's condensation

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Only diesels in this driveway.
2005 E320 CDI 243k Black/Black
2008 Chevy 3500HD Duramax 340k
2004 Chevy 2500HD Duramax 220k

It's not cold in this part of the country and does it even after the engine is hot. Hopefully it's something harmless.

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1967 W110 Universal Wagon, Euro, Turbo Diesel, Tail Fins, 4 Speed Manual Column Shift, A/C
1980 W116 300SD Turbo Diesel, DB479 Walnut Brown, Sunroof, Highly Optioned, 350,000+ Miles

Yeah I'd bet it's something leaking on the exhaust. See if it's the valve cover dropping into the exhaust manifold

__________________
Only diesels in this driveway.
2005 E320 CDI 243k Black/Black
2008 Chevy 3500HD Duramax 340k
2004 Chevy 2500HD Duramax 220k

Is the a/c on? The condensate may drain onto the exhaust.

I've been thinking about it, and maybe the windshield washer fluid reservoir is dripping onto the exhaust. It apparently has a leak. I'll have to investigate. The sound has been happening even before the air conditioning was working.

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1967 W110 Universal Wagon, Euro, Turbo Diesel, Tail Fins, 4 Speed Manual Column Shift, A/C
1980 W116 300SD Turbo Diesel, DB479 Walnut Brown, Sunroof, Highly Optioned, 350,000+ Miles

I think I found out what this noise is. I was under the car today while the engine was running and I noticed that the hose that goes from the power steering pump to the rear axle moves away from the oil pan and then slams back up against it in sync with the "hiss" noise that I'm hearing.

The hiss noise is coming from the back of the car, at the corner away from the exhaust. It's on the right (passenger) rear and sounds like it's coming from the valve/pump/whatever that connects to the rear axle. It keeps going HISS...HISS...HISS...HISS...

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1967 W110 Universal Wagon, Euro, Turbo Diesel, Tail Fins, 4 Speed Manual Column Shift, A/C
1980 W116 300SD Turbo Diesel, DB479 Walnut Brown, Sunroof, Highly Optioned, 350,000+ Miles

For anyone wondering, it was a malfunctioning ASD system, most likely from a bad accumulator.

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Stop paying for animal enslavement, cruelty, and slaughter. Save your health and the planet. Go vegan! I did 18 years ago. https://challenge22.com/

DON'T MESS WITH MY MERCEDES!


1967 W110 Universal Wagon, Euro, Turbo Diesel, Tail Fins, 4 Speed Manual Column Shift, A/C
1980 W116 300SD Turbo Diesel, DB479 Walnut Brown, Sunroof, Highly Optioned, 350,000+ Miles