Tech / General EngineIs your car making a strange sound or won't start? Thinking of adding power with a new combination? Need other technical information or engine specific advice? Don't see another board for your problem? Post it here!
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Okay... I decided to install a new CD player into my car. While I was putting it in, I moved the HVAC thing like 1/2 inch. It started making very LOUD hissing noises... then it stopped?! Now whenever it has been on and I turn it off, it makes some very faint hissing noise for like 5 minutes AFTER it is turned off? Sometimes when I start my car (without the HVAC on), I hear like a click and then the hissing for a second... and sometimes it 'randomly' hisses?! Whenever it starts it, I can move the slider from OFF to MAX and it will stop the hissing?! Could this be some type of vacuum leak? If so, how could I find/fix it? Also, my windshield seems to fog up all the time!
I would say yes you have a vac leak. Does the selector actually work, like does it direct the air to say the winshield when set to defrost? If it does not then you have a big leak and this is why your winshild would fog up.
If it does work and deflect the air to the proper place, you have a small leak and a dab of rtv on the outside should take care of the problem, that is if you can locate the leak.
If you are getting fogged up winsheild all the time, you could have a leak in your heater core. Do you smell any faint wiff of antifreze? If so then you have a pin hole leak and it is only going to get worse.
It is completely normal. It would be defective if it didn't do that.
All the little doors that control the movement of air, use vacuum as their "power" source to open and close them. The hissing noise is the sound of air moving in the lines as it gets routed to the different doors.
The windshield fogging up is one of 2 things; either there is so much schmutz like old leaves and dead bugs and dirt built up on the surface of the A/C evaporator and holding water, that it steams whenever it gets warm (this will make it fog up bad for a long time after you use your A/C, including in Defrost, and then turn it to Vent or Heater); or you have a heater core leak, and need a new one of those.
__________________ "So many Mustangs, so little time..."
you mighta' "disturbed" the vacuum manifold connection on the back of that vacuum switch. with the age of your car, that will develop a sloppy seal over time (gets dry). best thing to do is remove that connection off that switch, put some vaseline on a q-tip and swab the inside of each of those lines (5 of them, i think). replace the connection and op check it. the connector is held on to that switch by those goofy washer things that you just pry off and push back on. it's easier to accomplish with no stereo in the way, and i'd recommend to put a towel down in the area so if you drop that washer thing, it won't go far...
