Alfa 75 Strange hissing/suction noise in dash

Hi,

Another strange problem on my 75 TS.

When the engine is started, I can hear a strange hissing/suction noise from somewhere behind the dashboard/centre console.

The only way I can describe the noise is that it sounds like air or water being sucked into somewhere....

I can't hear anything from inside the engine bay (probably because of the noise of the engine).

Does not appear to affect anything, but is really annoying and I'd like to make sure this is not a sign of imminent failure of something somewhere..... ?

There is also a problem with the power assistance to the brakes/power steering on startup (see my previous message for more details).

Could the two problems be related ?

Anyone any idea as to what this strange hissing/suction noise could be?


Thanks.

Without listening to it, possibly the centre bearing on the propshaft?

sounds like heater matrix

heater matrix? never heard one of those making a noise. Prop centre brg certanily a possibility. I don't think there are any vacuum controlled bits in th dash are there?? I've recently connected up the vacuum ww/washer button on my old Jag the wrong way round and get a terrible hissing!

Hi All, many thanks for your assistance.

Are there any other tests I can perform to confirm a problem with the propshaft centre bearing ?

Is this an expensive/difficult job to sort out ?

Originally Posted by Wrenched

heater matrix? never heard one of those making a noise. Prop centre brg certanily a possibility. I don't think there are any vacuum controlled bits in th dash are there?? I've recently connected up the vacuum ww/washer button on my old Jag the wrong way round and get a terrible hissing!

Nope, nothing vacuum controled behind there, just italian electrics!

Originally Posted by roti155

Hi All, many thanks for your assistance.

Are there any other tests I can perform to confirm a problem with the propshaft centre bearing ?

Is this an expensive/difficult job to sort out ?

Probably just check for play and/or dry bearings. Not too difficult to do, you might manage to highlight it with a mechanics stethescope(sp) or a screwdriver held to your ear and pressed against the component......

there are lost of pipes on the inlet side on a 75, maybe one has a split, but that shows up as a whistle if small, may be worth taking time to inspect and put on new jubilee clips to ensure its not that. Running water sound if the coolant is low and the water goes through the heater matrix, I also had this sound when the head gasket was going in a Saab and the exhaust gas was leaking into the coolant. Any evidence of HG fail, eg steam from exhaust, coolant loss, petrol fumes in expansion bottle or bubbles in there when revved?

HTH