420 SEL, cracked rocker arm - advice needed.
 

My 420 SEL "died" the other day and I had it towed to a local repair shop.

This same shop had just recently done a timing belt/tensioner/guide change. According to them, it now has a cracked rocker arm. The shop wasn't clear if there might be more damage.

They stated the timing belt had not broke, and timing still set OK.
They also said they would "do the repairs under warranty" since they did the recent timing belt work which might have resulted in the damage.

Any thoughts on what might have happened?

And anything I should be concerned/ask about once they fix it?

Even though their agreeing to fix it under warranty, I must admit I'm nervous about what went wrong in the first place and will it happen again....

I would take it to another shop if they are using the word "timing belt" in describing the work they did to this engine - this car has a timing chain. I can't say I have ever heard of a "cracked" rocker arm shutting down an engine.

You have to wonder if the cracked rocker arm is not the cause of the problem, but just a symptom. Any bent valves? Despite the assurances you have received from your shop, I would wonder if the timing chain broke or jumped a few teeth on a cam. Bad tensioner?

My mistake, I meant timing chain.

I was wondering also about anyone knowing if a cracker rocker arm alone would prevent the engine from turning over.

The chain, guides and tension were replaced, but the shop guy gave no indication of any other problem found other than the rocker arm.

I'd be worried. A cracked rocker would simply mean that the related valve would stay shut, and you'd lose that cylinder, not the whole engine.

If the rocker had broken and the broken off part has circulated in the engine and jammed up somewhere, who knows what has happened.

I'm not a mechanic, just an amateur, but if I had changed your chain, and then a rocker broke, I wouldn't consider this a warranty job.

My guess is that they have screwed up, and are going to fix whatever it is they aren't telling you. I just hope they get it right this time!