Hi guys.
500TA 85hp manual.

Just driving gently along, no specific speed or specific gear or specific time of day, I hear a hissing sound lasting maybe 3 seconds. No faults, no problems. Happens every now and again even on the same journey.

It's not loud, fairly quiet, like air being released gently.

Any ideas what it is?

Regards,
Mick.

does the turbo have a dump valve?

Mick F said:

Hi guys.

500TA 85hp manual.



Just driving gently along, no specific speed or specific gear or specific time of day, I hear a hissing sound lasting maybe 3 seconds. No faults, no problems. Happens every now and again even on the same journey.



It's not loud, fairly quiet, like air being released gently.



Any ideas what it is?



Regards,

Mick.

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Climate control compressor I'd reckon

Thanks guys,

Certainly not a turbo valve, the sound is inside the car somewhere. I thought initially it sounded like an airbag filling gently!

ACC compressor might be it, though I have no idea what one is!

Regards,
Mick

My guess would also be the aircon compressor. Unless you don't have aircon?

The aircon is just a fridge, just like in your kitchen, same system, same gas, same process. To cool the incoming air it has to compress the gas as it is pumped around, and as it evaporates it cools the incoming air. This will create a few hissing type noises, and possibly a gurgle. All normal.

Turn off the aircon and the hiss should disappear, turn it on again and it will return. If this works, relax and enjoy the cool fresh air.

Our other car is a Clio with aircon, but manual temp control. She's done close on 95,000 from new and the aircon has hardly ever been off. Not once have we heard any hissing.

The 500TA has ACC - and we leave it on - and something hisses.
I must stress, that the hiss is very gentle and quiet - more of a long sigh than a hiss and it only happens every now and again.

No problem with this, just curiosity, and wondered if anyone else hears it.

Thanks,
Mick.

As you have automatic climate control my guess would be that the air distribution flaps are changing position, which is fine btw it's normal operation.

These maybe vacuum controlled or as they opening / closing you can hear the air flow as it becomes constricted.

AH!!!
That sounds right!

Vacuum control, and I can hear the air filling/releasing.

Excellent!
Mick.

Or a snake in the grass?

Sounds like air con noise to me, as mine seems to do something similar - but at random, not at any specific time.

Just thought I'd update this thread, as it suddenly struck me that the hissing noise had stopped some time back. Still no real idea exactly what it was.

If you go to another thread of mine:
https://www.fiatforum.com/500/418622-smoother-running.html

I had driven 250miles north to Derby from Cornwall, stayed overnight, then driven back. Since then, our 500TA is much better and smoother and quieter and even nicer to drive.

Also, the hissing has completely gone.

Regards to all,
Mick.

If you normally do short journeys then a long run always does a car good.

scout said:

If you normally do short journeys then a long run always does a car good.

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That's fine, but you can never get back before the chips are cold !

werdna said:

That's fine, but you can never get back before the chips are cold !

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You have to take the long way there and the short way back