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Humming when car is off + coolant leak.

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Old Jul 28, 2023 | 01:36 PM
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1987bigbirdie's Avatar
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Humming when car is off + coolant leak.

What's up Smart People?!
New to the club. We have a 1987 Firebird 5.0, 305, fuel injected. We just resurrected it after sitting for a time. We drove it and turned it off after it's virgin run. When we came back to it there was what sounds like an electric motor behind the passenger front fender/passenger dash area. There was also a small coolant leak that appears to be dripping from under the car in line with the dash, riding the exhaust pipe on the drip flow. If I turn on the AC (or really just the control *** out of the off position) it'll turn off for the duration of the ride. But when I kill it, it turns back on. I disconnected the battery to stop it). Doesn't seem to leak coolant when it's not running.
Heater core? Something else? Any thoughts/ suggestions for diagnosis or fix. Limited budget, currently triaging fixes. Even a temporary disabling would be helpful till we can see what else is gonna break. Thanks in advance.
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Old Jul 28, 2023 | 01:52 PM
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Re: Humming when car is off + coolant leak.

Sounds like hvac blower motor is running, it should have no power going to it in the off position so probably a bad switch. The coolant leak you should lift the car and look by coolant hoses at bulkhead going to heater core.
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Old Jul 28, 2023 | 01:53 PM
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Re: Humming when car is off + coolant leak.

To temp disable the blower motor unplug the blower motor under the hood at motor or try unplugging the resistors in the hvac box under hood passenger side.
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Old Jul 29, 2023 | 11:28 AM
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Re: Humming when car is off + coolant leak.

Originally Posted by Tuned Performance
To temp disable the blower motor unplug the blower motor under the hood at motor or try unplugging the resistors in the hvac box under hood passenger side.
Thank you so much! I’ll try it. I’m sure I’ll be back with more questions. Thank you for your generosity of time and expertise.
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Old Aug 7, 2023 | 05:43 PM
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Re: Humming when car is off + coolant leak.

Hey folks, we tried unplugging the HVAC motor (the 2 plugs to the front of the motor, pass side, against the fender) and there is still something running. It is in the vicinity of the HVAC motor, but it sounds like it is behind it, deeper in the dash. Any other suggestions? I will try and include the video later, if possible.
Thanks again
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Old Aug 8, 2023 | 05:20 PM
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Re: Humming when car is off + coolant leak.

Originally Posted by 1987bigbirdie
Hey folks, we tried unplugging the HVAC motor (the 2 plugs to the front of the motor, pass side, against the fender) and there is still something running. It is in the vicinity of the HVAC motor, but it sounds like it is behind it, deeper in the dash. Any other suggestions? I will try and include the video later, if possible.
Thanks again
Just Curious, , , does this car have a power antenna?
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Old Aug 9, 2023 | 09:50 AM
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Re: Humming when car is off + coolant leak.

Originally Posted by OrangeBird
Just Curious, , , does this car have a power antenna?
Good question. Had that problem with a 1981 Cutlass power antenna trying to raise & it drained the battery. Pulled the antenna up manually with a hook & disconnected power.
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Old Aug 24, 2023 | 06:37 PM
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Re: Humming when car is off + coolant leak.

Originally Posted by OrangeBird
Just Curious, , , does this car have a power antenna?
YEESSSSS!!!!! That was it! So simple. Thank you. I just have to address the coolant leak now. It appears to be coming out the heater core. Is there a way to cap it temporarily until I can address it? Do any of you geniuses know which hose is the correct one? I'm assuming the one that goes to the fire wall, passenger side of the engine. Best way to cap it? Thanks again!! I'm so grateful.
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Old Aug 24, 2023 | 06:49 PM
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Re: Humming when car is off + coolant leak.

which hose is the correct one?
There are 2 hoses going to the heater core. One is 5/8" inner dia, one is 3/4" ID.

​​​​​​​Is there a way to cap it temporarily
Disconnect them at the firewall and stick something in them of those diameters. Pretty straightforward really. Probably not hard to find something at any hardware store. Metal is better than plastic.
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