Charles' "distant tornado" sound


#1

Tom and Ray said this might have to do with a bad motor mount or exhaust leak at the downpipe. They missed the obvious answer of a properly-working radiator fan clutch.



Charles described a ‘distant tornado sound’ for ~30 sec. after starting the car. The fan clutch is locked for the first ~30 sec. while the silicone redistributes itself around the inside of the spinning clutch. After ~30 sec., the silicone is distributed correctly and the clutch releases, allowing the radiator fan to freewheel.



Charles also said the noise comes back when he comes to a stop. Sitting at a stoplight, the radiator fills with hot coolant (no longer cooled down by the forced air of driving), and the fan clutch heats up and locks, allowing the radiator fan to spin at full speed, causing a ‘distant tornado’ sound.


#2

Volvos have a Secondary Air System air pump that runs for a minute after the car is started. The pump feeds air to the catalytic converter to help it heat up quicker. An error code of PO 410 will come up on the OBD II reader when the air pump or the SAS valve fails. Often the SAS valve will stick, allowing water condensed from the exhaust to run into the blower causing the blower to fail, it will get louder and louder until the blower motor fails, then you get the error code.

A distant blower noise is normal though, for the first minute after starting the motor.

As for the noise happening with sudden stops, I can’t really say, a bad fan relay maybe?

Dave


#3

What about the turbo?? He didn?t say if it had one, if it does I have the same noise when my turbo started going out.


#4

On my V70 I would get a sound like this when the headlight wiper blade gets stuck. The motor will try to move the wiper for a while and then stop. I don’t know if S40’s have this, and it doesn’t explain it happening at the stoplight, but it is easy to check.


#5

This concern brought alot of people to the Chevrolet dealer I worked at in the mid-90’s.They thought the trans was slipping,it was the fan clutch,most common on the S-Blazer


#6

That was my thought when I heard the description of the sound Dave…good catch (this coming from a V70XC, 960, 740 owner).