I own a Jaguar XJ6 1995 and it always has a LOUD squeaky sound, Ive replaced both belts and the only time it stops squeaking is when I put on belt conditioner but then in around 10-15 mins it starts squeaking again so I have to be putting belt conditioner all the time. Any Fixes?

 

Sounds like you might need a crank damper rebuild.

There are many threads about marking the pulley and see if the marks move from alignment. This is the way I check the damper.

Damper Doctor
or
Dale Manufacturing

bob

 

Check your harmonic balancer , all you'll need a piece of white chalk and instructions you can easily find on the Web . If you need a recommendation of a rebuild I'll send it to you .