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Groaning noise after car turned off

My '01 Corolla occasionally makes a soft groaning noise after the car is in park and turned off. It doesn’t happen all the time, and I haven’t been able to correlate it with anything. The noise seems to be coming from the front somewhere. I took it to my mechanic but of course it wouldn’t do it for him. Any idea what might be causing this?

How many miles, and is it manual or auto transmission?

About 73000 miles, automatic.

How long does that groaning noise last?
Is it at all possible that the noise is coming from the back of the car?

I ask these questions because the e-brake/parking brake can emit a very brief groaning noise if it is not applied firmly. In a situation like that, the car will roll very slightly until the “Park Pawl” in the transmission stops the car from moving, but until the Park Pawl stops the car, a loosely-applied e-brake can emit a groaning noise.

I almost doubt that Carollas have this but It doesn’t have some sort of stability control/adjustable shock mechanism, does it?
Some older Datsun Z’s had some sort of issue where the shocks would adjust for hight, even when parked. It looked like the car was alive but it was an electrical issue. A buddy of mine named his car Christine after seeing that. It looked cartoonish: he’d get out of the car and seconds later it would sag down a bit, like it was sad to see him go.

The vacuum reservoir can crack and cause such a noise.

Sounds like sticky brake caliper slides or piston/s .

When you park the vehicle the brakes are applied.
You could be just hearing the brakes creak until the vehicle load comes to rest on the parking prawl.

The groaning noise generally lasts - oh, I would say a few seconds. And it seems like there’s a bit of a pause between when the ignition is turned off and when the noise starts. I think it’s coming from the front but I could be mistaken. No idea about an adjustable shock mechanism…

A in NJ–
Try applying the e-brake very firmly, and then see if this groaning noise is heard.

My heater /ac makes some noise as the vacuum depletes and the system returns to zero.

My guess a bad radiator cap and possibly clogged coolant tank return hose, 10 bucks worth a shot though as it is a replicable event it should not be hard to diagnose.

If the noise is coming from the front of the car, I wonder if it might be the radiator cooling fan. If the fan was running just before turning off the car, you would hear the noise. If the fan was not running, you would not hear the noise. If I am right, the radiator fan probably has a bad bearing. With the car cold and the key off, try spinning the fan by hand. You may be able to confirm whether or not the fan motor has a bad bearing.

At first I was thinking AC, they often make this noise when you shut off the engine, but Triedaq maybe on to something. there are two conditions under which the computer will turn on the cooling fans, one is when the coolant temp exceeds a preset temp and the engine is running.

The other is after the engine is shut down and the coolant temp exceeds a preset temp. It is normal for the coolant temp in the engine to rise right after the engine shuts down so the fan may not start up for several seconds, even up to a minute after shutdown.

Open the hood, stick your head under there, have a friend shut the car off under the same conditions as when it groans, and see if you can identify where it seems to be originating from. That’s the first thing I’d do, and you’d be amazed how often the source of the sound is obvious with the hood up.

Well, as I said, I haven’t been able to figure out what causes the noise to happen, because it doesn’t happen all that often. But, my commute to work is only about 4 miles. The last time I heard the noise was after a 20 or 25-minute drive to a friend’s. So I’m liking the cooling fan idea.