2002 SL500 OBD shows no codes. Will not hot start
 

My first guess is the crank sensor...

Drives beautifully until I park it. If I don't give the car 10 minutes to cool down it will not restart.

No codes show up on the OBD reader. By the time I get the engine cover off and pull a spark plug the car would have righted itself.

My thoughts on the culprit, in this order, are Crank senor, Cam Sensor, and MAYBE mass sensor but I wouldn't think the third would cause this.

Thoughts?

I would second your first guess :D
the only sensor that wont set a code is the crank sensor as it sets the mark for all of the other sensors! fairly typical symptoms although they usually get worse fast - taking longer and longer to reset from hot untill they just dont work at all.
cheers
Barri

When my crank position sensor failed, it took me several days to finally getting around to replacing it.

I had several hot start problems over those few days, and it never set a code.

Check for fault codes during the same key cycle as the no-start condition occurs. In other words, let the no-start occur, then check for codes before turning the key off/on.

Unfortunately I don't have a reader handy; rather I have to go and borrow a friend's while at his shop.

I was driving the car, and came upon a busy interstection with a long wait for a light. It died... I had a some water with me, so I got the bright idea to pop the hood, dump the water on the sensor, and see what happened. Since the problem was heat associated I thought it was worth a shot. It started immediately. :D

I changed the crankshaft position sensor this morning and all is right in the world again. Warranty time said 30 minutes, and I had i swapped in under 15... Having long skinny fingers helped, as it has a lovely heat shield around it.

The thing sort of looks like a crack pipe. :D

That's exactly what the MB roadside guys do! It's not exactly high-tech diagnostics, but it works. Good for you.