Hello.

Today I got out of my truck and for the first time I noticed this hissing sound coming from what looks like the center of the truck (between the cab and the bed). I guess it can pass as a puffing sound as well but to me it sounds more like hissing.

It would hiss air, stop, then hiss again. This went on for a few minutes and I decided I needed to go back inside the house before I froze to death. For all I know it's still doing it now. I checked all four tires and it definitely is not losing air.

Does anyone know what this could mean? Is it a problem that needs to be checked?

Any help or even opinions would be greatly appreciated.

 

Was the exhaust hot? possible water draining from the bed or running down from the roof and contacting the exhaust somewhere?

That's a hard one to help on without actually being there

 

Yes, the exhaust was definitely hot as I was driving around doing errands all morning. I forgot to mention I checked out the exhaust pipe and no water was dripping onto it. Could it be water dripping onto another hot spot of the car? Oh yeah it was raining all morning here (Northern California)

 

Well with a hot exhaust and a rainy day I would really suspect some moisture got somewhere on or around the exhast somehow. But you'll probably have to do some testing to find out the exact cause. Like I said it's hard to diagnose a noise without actually being there but it seems you've covered all the basics. Checked all 5 tires (yes check the spare too) for leaks, no smell of fuel, no moisture contacting exhaust and the leak isnt happening while running I (i.e. fuel pump noise, exhaust leak ect) It's gonna take some pinpointing. Keep driving it and see if you notice any similarities when the noise happens.

 

I would also check all your vacuum lines in the dash. They just slip on and could easily have been unplugged causing a hissing sound. I would see this as a pretty likely scenario.

 

what was the temp out? could be the EBPV valve mal-functioning?