Hissing noise from rear of vehicle when car is turned on

Thump + hiss, moving, is a very bad sign.
why not get the car inspected by an ASE tech, mech.
?????
we can not do noise here. only real ears, (in stereo) work.
and lots of other checks.
get is serviced , it might not be safe to drive it.
or is about ready to have a cascade failure.

I had the same sound after reaserch I found it was the rear hub barrings, to check it take off the tire and pull on the lug nuts if the ole thing moves out and in that may be the problem item was cheep and easy to install it fixed my problem

Not the tires
Only makes a noise with the key on
or engine on
No idea without the car

what is the make and model? sounds like a bad master cylinder

CHECK THE TIRE AIR STEM.I HAVE SEEN THEM LEAKING.I HEARD A HISSING NOISE TOOK TIRE OFF SPRAY SOAP WATER SOLUTION ON IT LOOKING FOR A AIR LEAK.DID NOT SEE IT UNTIL WHEN I PUT HUB CAP ON.HOLE THAT THE AIR STEM GOES THROUGH HIT AGAINST AIR STEM HISSING GOT WORSER LOUDER THEN I FOUND WHERE LEAK WAS.SO CHECK AIR STEM TO TIRE MOVE IT A LITTLE SEE IF YOU HEAR HISS NOISE.

Sounds like you have something rubbing, since you are not loosing air and there is nothing else to hiss,, an exhaust leak would have a different sound. I have seen debris get wedged in the brakes and make a noise when you are underway. The sound would vary, depending on what sort of debris it is. I would remove the wheel and look for the culprit. Your brakes may need to be religned as well. Sometimes the audible brake wear sensor will make a noise like that. Good Luck! I hope this is very helpful!

probabbly not the brakes, maybe the tires but u need to check that, if u hear that noise with the engine running it might be a burned out gasket on your exhaust line
hope this helps

ry checking the condition of your wheel bearings they may need servicing or replacing and cv joints

It sounds like a possible bad front wheel bearing they will make like a humming or growling noise.The pull could be air pressure a little lower in the right front tire than the left front check the air in all tires and if pull is still there take the left front put it on the right front and put the right front tire on the left front.Sometimes tires get what they call radial pull and that will fix it or make it go the other way if it goes the other way either get new tires or put the back tires on the front of the vehicle and put the front tires on the back.

yes that is the expansion valve! there is a hissing sound from the restriction in it for a pressure drop thats what makes the a/c cold the hissing is normal