Car squeals like a belt loose when just starting to push on gas and then stops. Continues throughout entire drive warm or cold.

 

Presumably you've checked the belts and they are tight, yes?

There's a decent chance that you harmonic balancer is delaminating. Most of us send 'em out to be re-bonded. Fairly common problem.

If you search the archives under "Balancer Delamination Squeal" or similar you should got lots of hits.

Cheers
DD

 

you can also take the belt off and feel for bad/crunchy feeling bearings in all you accessory's and idlers.

 

If your belts are the standard V belts. The pulley could be worn to the point the belt is riding in the bottom of the pulley, and not making good contact on the sides where it's suppose to. Take a new belt, and turn it inside out, then insert into the pulley so you can see how deep in the groove it will go. If the bottom flat/ narrowest part of the belt touches the pulley, it is worn, and should be replaced. If it is worn, It is very likely the cause of the squealing. Hope it helps.

Jack

 

I'll add that on the 96 XJS there was a TSB for a timing chain tensioner to be replaced and that stopped the squealing on start up and 90% of the intermittent squeal on random acceleration (doesn't happen every time) for me. The tensioners are fairly cheap and still available. But, I will be trying the white out line across the pulleys to see if the harmonic balancer is playing a role.