1985 300 SD in well-cared-for shape. Car runs fine, no complaints with that. But when cruising at any speed with any or all of the windows or sunroof open, the smell of diesel exhaust comes into the car. This doesnt happen with the windows and sunroof closed, so I know it doesnt have an exhaust leak.

It is mind boggling (to me, anyway) that at 70 MPH on the freeway with all the windows closed but the sunroof open, that the exhaust fumes somehow travels up over the rear bumper & tail light panel, forward over the trunk, rear windshield, back section of roof and finally into the cabin! How is this possible?!?!


What would you suggest to remedy this issue, I am completely stumped.



NOTE: Prior to my ownership, somebody had replaced or re-welded the rearmost section of exhaust pipe and it isnt 100% aligned perfectly, but its really close. I cant imagine that would cause this issue, but I've been wrong before. Can anybody knowledgeable with these cars or this general situation, chime in here & enlighten me?

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2007 Dodge Ram 3500 Cummins Turbo Diesel 4x4
1994 GMC S-15 pickup 4.3 5MT
1985 300 SD
1978 300 CD
1962 220-S Fintail - awaiting restoration

That's interesting logic.....have you actually checked? You probably won't smell exhaust with everything shut if the leak is rear of the intakes below the windscreen.

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1978 300D, 373,000km 617.912, 711.113 5 speed, 7.5mm superpump, HX30W turbo...many, many years in the making....
1977 280> 300D - 500,000km+ (to be sold...)
1984 240TD>300TD 121,000 miles, *gone*
1977 250 parts car
1988 Toyota Corona 2.0D *gone*
1975 FJ45>HJ45
1981 200>240D (to be sold...)
1999 Hyundai Lantra 1.6 *gone*
1980s Lansing Bagnall FOER 5.2 Forklift (the Mk2 engine hoist)
2001 Holden Rodeo 4JB1T 2WD

Look at the rear bumper mount surrounds ~ whey they're damaged / missing or loose, the exhaust fumes get sucked into the trunk thence the passenger compartment ~ look at the carpet on the parcel try around the first aid kit ~ there's usually some amount of exhaust smoke staining it .

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-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better

Check your connections under the hood....at the down pipe to manifold connection and especially around and in the flex pipe. Leaks there are hard to find sometimes.

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

wish I could smell it again,really liked my KFC oil,burning in the motor

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1999 w140, quit voting to old, and to old to fight, a god damned veteran

When that happened to me in my 300SD, it was the plastic vent pipe that fits into the top of the air cleaner with a rubber plug; had to replace the plug and all is well.