Hey guys-

I've got about 7k miles on my 05 5.4 and I notice after I turn the truck off it sounds like the engine is letting off some sort of pressure. Even if I just move it in the driveway it still makes a fair amount of noise for a few minutes after shutdown.

Any ideas on what could cause that? Vacuum hose leaks?

also, not sure if it is related, but I get a clankingknocking sound when I start my truck...sounds bad, and randomly (about 1 in 10 to 1 in 15) when I attempt to start the truck it fails to turn over all together. Dealership claims nothing is wrong.

 

the hissing sound do you notice is when the a/c is on? If so it is probablydue to the freon draining out. No biggie it happens to almost every vehicle.

 

Thats probably it. Actually it's the A/C equalizing the pressure.

 

what he said

 

Actually, no lol. I usually DO NOT run the AC. I typically have something on...but especially this time of year AC is very rare in my truck. I prefer windows down...

So any other ideas? heh

 

Isnt freon like......dangerous?? Where the heck would it leak out? I dont want the neighborhood cat or somthing dieing on my driveway(wich i find funny cause I PARK on my DRIVE way)

 

Doesn't matter; the compressor runs all the time in new vehicles from what I understand.

 

The compressor only runs when you are using the A/C, or the Defrost. The A/C is of course to cool the truck. The defrost is to remove moisture from the air.

The hiss is normal. It's the high side leaking down into the low side. Everything does it.

We don't use Freon anymore. We use R134. It’s far more dangerous than Freon, but more politically correct. It's a sealed system. If it was leaking enough to hiss it would be empty in less time than it takes to read this.
Chris

 

The refrigerant is not leaking out, it is leaking from the high pressure side of the AC to the low pressure side.

The compressor runs all the time on vehicles with automatic temperature control (I think Lariet and higher). Otherwise,it works when the little AC switch is pushed (mine is on a lot of time and I don't realize it) and when the defroster is on. Look for the little light on the switch.

 

Sorry if I gave the wrong info. Actually that is almost all the time in the South.

 

It's normal. Don't worry about it.

 

Cool, thanks guys!