Hissing Sound?

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mrichard

mrichard

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So just recently, as in last evening, I have a noticable hissing sound coming from what sounds like right in front of the dash/firewall - although I can't confirm location.

When I have heard this in other cars it usually means my brake booster is going. Trouble is with this car I have no power brakes and no brake booster.

The car is a 72 Base Dart, so NO power brakes, three on tree (it has a clutch - maybe that's it? seems to change a bit when I put the clutch in, although again not entirely sure). Its a slant six, no A/C.

I would appreciate any help here you can provide.

Mark
 
It sounds like a Texas Rattler, get the hell out of the car!!!!!!!!!!!!!!!
 
If the clutch needs adjustment you might be running the throw out bearing at all times. If that is the source of the noise just the slightest move of the clutch pedal will stop or at least change the sound.
You can also use a piece of tubing to listen around the intake and narrow down the location of a vacuum leak. Hope this helps
 
Thanks. Had to laugh on the rattler comment. Let's hope it's not that. Although that rattler dies down after the key is pulled.

I'll check it out more thoroughly this weekend. Anyone have simple instructions on the clutch adjustment?
 
Sounds like a leaking servo in the HVAC box. Of course in your circumstance, it's just an HV box.
 
Quick and easy.. The Adjustment is made at the rod at the bell housing. Give yourself about 1" free play at the pedal.
 
Thanks all for the advice. I actually learned a lot about a few other things I need to do anyway like the clutch adjustment. Turns out it was a hose that came loose under the aircleaner. I'm not sure what that's called that it's attached to, but I stopped for gas this morning and finally had daylight to sniff around in there. Found the house detached, reattached it, and presto, hissing stopped. Can anyone tell me what the hoses do that go into and out of the aircleaner? I know that's a "stupid" question, but I've been trying to figure that one out.
 
72 was the start of the EPA getting into American auto manufacturing and the era of million miles of vacuum hoses, sensors, delays,timers, etc. Be thankful that your car is a 72 and not late 70's. I am sure someone here knows just what the item in the aircleaner is and what it does.
 
If it's that little round thing inside the air cleaner that's about the diameter of a quarter & has 2 hoses hooked to it, I think it's there to measure intake air temperature & help determine when to open & close the heat stove attached to the air cleaner. It has a bi-metal spring that controls vacuum to the valve on the intake of the air cleaner. That valve is what controls the heated air coming from the exhaust manifold through that big (2" or so) tube up to the air cleaner. I could be completely wrong though.
 
thermostatic air cleaner

This system regulates air temperature flow into the engine. The thermostatic air cleaner system is designed to draw heated air from around the exhaust manifold of the engine during a cold engine "start-up" and as the engine warms up to normal operating temperature, a valve changes position to let cool air enter the engine.
Some related parts of a thermostatic air cleaner system can include, but not limited to: exhaust manifold heat shroud, hot air pipe (tube), air door (valve) assembly, vacuum diaphragm and hoses, and a temperature sensor.


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