exhaust smell

Get under the hood, look for carbon build up, look for smoke & sniff, sniff, sniff...get it fixed. Areas of focus, flex pipe connection bands. exhaust manifold. egr turbos...look over their bolts n seams.

 

You don't say if you've done anything to look for a leak or where it's originating from. Have you?
What I'd do is check first for oil leaking in the engine compartment, possibly onto hot manifold or exhaust parts, as well as checking both by feel and sight around the entire length of your exhaust system, especially at joints/connections. Pay close attention to any flex pipes also.
Also look for traces of soot and loose clamps, or other signs of a leak.
With 20 years, I would think you know these basics. I don't know of any "Volvo specific" exhaust problems, other than basic ones mentioned.

 

there was bulleten about crancase vent hose on D12C engines on conventionals and cabovers. really easy deal to make it longer, becouse sometimes HVAC system sucks smell inside cab, usually when engine goes older and burns oil a bit. Usually I see this problem with '98-02 trucks, generally with conventionals

Other sourse of smell - exaust manyfold leak and turbo gasket leak. Easy to find poit of leak by black carbone deposits

 

check the top sides of the long Y pipe, mine corroded thru, and it was drawing the fumes back into the cab as you describe,. The rotted spots were not visible just looking from underneath, I had to get my head up to see the top side of the pipe.

 

More than likely it's the flex pipe at front of exhaust where it first goes under cab up front. I had same problem, but I never noticed the split because it was where I couldn't get my fat #ss far enough under to see it.
Not a cheap piece of pipe either.

 

If the OP owns the truck from photo avatar, looks like a Volvo 770; doesn't have the same stupid designed expensive flex pipe from D13;
I spent lots of $$ on my Volvo D13/2008 fixing exhaust fumes leaks caused by back pressure, DPF regen, EGR; I installed a CO2,carbonmonoxide,smoke detector in my cab ; I replaced the manifold 4 times, once was covered by warranty, after I paid 2000-2400$job; the flex pipe maybe 7-8 times, cracks in DPF housing; joints from EGR and egr cooler; I still have a smoke leak, I feel in my cab and I can't find it; took the truck in 5 Volvo shops they can't figure out where is leaking when the truck is parked; I bought a wireless webcam, I'm going to install it in few different suspected spots and watch on the laptop while the truck is moving pulling harder;

 

KW cajun...............Lets do some physics here.

Lets say we have a driver whom is brave enough(or crazy enuff) to tackle a mythical stretch of road as your profile picture depicts..

So lets see.....82% downgrade and 97 miles long....

Here is what will happen.. If and only IF jhe was able to control the vehicle for the first MILE.........Theres a good chance he will lose control and Flip it over going well over 100 mph and no brakes left.......

So, He will be laid over on his side, Thinking its all over...NOPE,, The next 96 miles he will be sliding down the hill...Thats over an hour and a half of being on your side going down the hill.. Grab your cameras people.



No, I did NOT smoke anything prior to this explanation.