Intermittent Exhaust Obnoxiousness

[Thermal Jock]

Hello,
Newbie here, sure like perusing the forum.
Have an intermittent exhaust smell in the cab when driving downhill. It's only when driving down steeper grades like mountain passes, and between 30-60 mph. Usually it's very faint, but yesterday coming down into Durango it was really bad. Rolling down the windows made it worse. I can't find any exhaust leaks. Rolling down the back window made it really stinky. I think it's an external airflow issue. Any ideas on exhaust routing or airflow mods that might help?
Also, have a large overhead rack on top the truck for hang gliders. I'm sure it's an airflow disturber, but I had the problem once in a while before I put the rack on. Thanks in advance!
Thermal Jock

[mirage]

I always get an exhaust smell real bad when I roll down my back window in my suburban. Same thing happened in my gasser blazer too. If you're getting an exhaust smell with the window up I'd check the exhaust manifolds and make sure they're nice and tight. Seems like the fumes would need to be coming from in front of the firewall to get them in cab. Once the leak in the exhaust is under the truck, I'd think that the air flow would keep you from smelling it unless it is really large.

[catmandoo]

i started to get one right after i replaced the clutch.figured it had to be the boot,and sure enough the inner bushing type sponge thing was out of place,popped it back in and no more smell,but i do have an 82 sub with a banks and if the right rear window is down it gets pretty nasty smelling sometimes.

[Thermal Jock]

Thanks for the replies! Went out and checked the exhaust manifolds, everything looked good. But crawling around under the truck at idle I can just catch a wisp of exhaust either on the passenger side manifold or where the turbo downpipe area is. Can't feel any leaks. Tried spraying it with soap solution but just made a mess, no leaks detected. I think you're right, it's in that area, I'll just keep looking.
Thermal Jock

[britannic]

You'll need to restrict the output for best results. Get something like a rag or similar and block the tailpipe with the revs up a little (jumper the fast idle), then check for leaks.

[Thermal Jock]

Found a small leak where the crossover connects to the manifold. Fixed it with high temp gasket sealer. So far, no smells! Hard to believe it gets in the cab.

This truck came from California. Has a Banks exhaust (I think, it's the right size) that probably was installed with the turb. Any way that would be a resrictive muffler? Could I upgrade just the muffler for cleaner exhaust?
Always fighting EGT's up 10,000 ft passes.
Thanks! for the help above.