Q: Siri drops bluetooth connection with 2006 Prius

Last week I noticed a new problem with iOS 8.1 on my old iPhone 5.

When I asked Siri to use Bluetooth to call a phone number using my 2008 Prius (which had been working for years)

the calls started being unexpectedly dropped before the number was dialed.

This weekend I updated to my iPhone 6 Plus, and the same problem continues.

I tried re-pairing the Blutetooth with  the Prius which works OK but the dialing and car audio stopped working.

Is this a know iOS8 problem ?

Thanks all