Bought this truck earlier this year, and started to notice from time to time a smell in the cab that can only be described as propane. Truck was sound and the windows were down most of the time so I let it go. Probably not smart. With the windows up more often now, I need to know if anyone has any idea what this could be. It comes and goes, and anyone I ask seems just as baffled as me. My guess is it's somehow coming through the vents, but what the heck is it? Is there anything in a truck that has mercaptan in it?

 

Not unless you're running NG or LP.

However, mercaptan smells a lot like hydrogen sulfide which can be produced in the converters under certain driving conditions. Similar smells can also be caused by the decomposition of certain organics.

 

Dead mouse!

 

Can you elaborate on that? Also, about what you said about the organics (and rmccbride suggested a dead mouse) I kind of doubt because I don't smell it all the time. And I live in a very old house so I know what a dead mouse smells like. If one kicks the bucket in a wall it can smell strongly for days, but then goes away. This has been the same smell off and on since I bought the truck.

 

LP and NG are odorless gasses. Mercaptan is added to give gas the smell we associate with a leak, to warn people to leave a building before a tragic explosion.

You're not using LP or NG so......

It is also described as a "rotten egg" smell which may have a lot to do with way your fuel is being burned. There's sulfur in fuel additives; your engine isn't burning it completely and your catalytic converter is storing it and then releasing it as hydrogen sulfide when you add load to the engine and force more air through.

 

1. Is this typically associated with a specific engine problem?

2. What's the solution, assuming there is one?

 

I would have to say check your battery.....and your alternator....Your alternator could be overcharging your battery

 

Are you sure that your not smelling a leaking heater core??

 

I don't know but would I still smell it in the summer with the air off and the temp selector all the way to cool?

 

Yes. Coolant always flows through the core unless you have a cutoff valve installed.

Antifreeze usually has a sickly-sweet smell and, while quite distinctive, smells nothing remotely like hydrogen sulfide.

1. Not really. Usually its due to either your selection of fuel, especially if you always buy fuel at the same place or ii it comes from the same refiner. Otherwise, it's an issue with the converters and your particular driving style.

2. Try a different fuel, preferably one delivered by branded delivery trucks rather than a jobber.

Overcharging battery is a good thing to check, as noted.

I will point out that, if the smell is coming from the converters and is entering the cabin while you are driving, that would suggest that you have an exhaust leak. While the rotten egg smell might be annoying, the prospect of carbon monoxide in the cabin from an exhaust leak is what should get your attention.

Now, some questions to hopefully isolate the issue.

1. Do you ever sense that smell when you get into the truck for the first trip of the day?

2. If you only smell the smell while driving, does it occur all the time or only after specific driving events (sharp acceleration, just after a stop, etc)?

3. Any evidence of an exhaust leak?

 

I will check for overcharging. If it is, is the voltage regulator inside the alternator or can it be replaced separately?

The thing that gets me is that the smell isn't constant, which I would think would rule out fuel (I do usually go to the same place).

1. I can't say for sure that I've never gotten it the first trip of the day, but I can definitely say I don't smell it when I first get in and start the truck.

2. Usually when I notice it it's at a stop. Cracking the windows for a few moments when I get going again gets rid of it.

3. Pretty sure no exhaust leak. No sound to indicate it. Definitely not from the muffler back, haven't checked forward of that visually.

Thanks.

 

Hello All,
My boss at work has been experiencing it on his truck as well. He's gone to multiple dealers who state there's been excessive use on the front axle. I would normally agree however, he doesn't even have a plow attachment which could cause such a problem. Upon looking at his truck, I quickly realized it's actually gear lube, not propane (they smell similar to the untrained nose). Not to mention, his truck doesn't have any propane mods/options. After speaking with him, I found out the front axle vent tube check valve has this common failure problem and the vent tube is routed near the brake booster where the intake for climate control is also present which, means the smell can migrate into the cab. I suggested he reroute/extend the vent tube to remedy the issue and possibly replace the check valve with a small breather filter to keep debris out of the tube. In reality, it's good the check valve has stuck open as, it's better to have the axle continuously venting than not.

 

Maybe someone filled your A/C with propane based refrigerant and you have a small evaporator leak?