Series 3 V12 AAV Orifice Size Differences

Hello - I have a 1992 V12 Vanden Plas (Series 3). The AAV was making a very loud whistling noise and the car has been running a bit rough when hot.
I bought a new Lucas brand AAV, listed for my car with the 5.3 litre. The new AAV has a much smaller orifice than the original one (seen here.) I know the one I took off either factory or dealer installed, as my car has 39,000 km on it and the gasket material was the dark red paper that Jaguar use to use.

As expected, when cold the engine will not idle unless I open the throttle a bit and when it’s warm, I had to crank out the adjustment screw on the AAV to get 650 rpm. Even with the screw out, it will not idle when cold.

Did I get the wrong AAV? How can I ensure I get the correct part number next time?
Can I make up for the smaller orifice on the new AAV by setting the throttles a bit more open at idle?


Yes, there are a few different AAV’s and clearly the replacement you’ve got it’s not the same.
Never the less I don’t think that is that important.

Aux Air Valve 001

The problem with your replacement AAV is that the top part/cylinder is pressed too far in leaving only a very small air opening when the valve is open/cold.
The problem is that in order to rectify this, i.e. move the upper part upwards, you have to dismantle the valve completely. If done carefully you might get away without destroying the thermal bulb. You will find all the details on Kirby’s book.
And you could even put the good working bulb to your old one.

An other option is to send your original valve to @John_John1 and he will fix it for you, or just get a replacement bulb and fix you original valve
AAV Bulb -30°C
Bosch: 1 287 230 002
F 026 T03 038
Mercedes Benz: 001 203 95 75

Having said all that, the AAV and your car running rough when hot are not related.
The only thing the AAV does is to regulate the amount of air on idle.