What happens to the TL VTEC engine if the timing belt fails? I have a 04 Passat V6 and have been told it is an 'interference' engine which means that serious damage can/will happen if the TB fails. Same with TL?

 

Yes

 

A slightly more complete answer:

An "interference" engine means that if the timing belt slips, the valve can come in contact with the piston. At a minimum this will result in a bent valve. More likely it will take out the piston and the rest of the engine.

Short answer.... Very Bad.

 

What kind of history does the TL have regarding this rather unfortunate occurrance?

 

no history...... I dont think there are many cars nowadays that have that problem....nor will they. the correct maintenance and care of the drivetrain should result in fun times n no worries.

 

There is a reason they say to change the timing belt at 7 years or 105k miles under "normal service" That leaves a safety margin
If you live where its really hot- has no ozone layer- pull a trailer- live high in the steep mountains, all those would be Severe Service and early replacement is advised.
Many members drive more miles and have gone 150k on the t-belt and then changed
Others drive very little and will change on age rather than miles. I have 80k now on an 01 so this year it will get done based on age.

IF it breaks- more than 1 valve is going to make contact and piston-rod- internal damage--well its cheaper to get an auto recycler yard (formerly junkyards) used engine, and replace the timing belt and water pump on it before install.
If in doubt- whip it out
Your wallet that is~