300 SDL Stuck Starter

[ccooper]

I now have another issue to add to my litany of starting problems. My starter motor attempts to spin, but makes a loud "GA-CHUNK" sound and stops, almost as if the flywheel was frozen. I recently replaced the starter with a remanufactured Bosch, and it has started flawlessly until now.

I eliminated the NSS and starter switch as culprits as I shorted the terminals on the solenoid, getting the exact same result. It is definitely not a bad motor, evidenced by the loud klank that shakes the car versus the much quieter "click" a solenoid attempting to start a bad motor makes. The condition of the glowplugs seems irrelevent as the starter doesn't even spin (the GP light does come on).

There are two things it seems it could be to me. I do have a cracked head, leaking coolant. First is the cylinders could be rusted. The second is the water vapor has fouled and plugged the catalytic converter. However, aside from the coolant loss, the car has run flawlessly and with no lack of power.

I just want to note why I'm continuing to run it, even with the cracked head. I work from home and only need to drive a 45 mile roundtrip twice a week, plus sundry errands, so the car is used regularly, but lightly. Being self-employed and growing my business, I want to put off purchasing a full-time car as long as possible.

I'm also intending to replace the engine with a used one from another car. My compressor is bad, the injection pump has issues, and so forth. For me, while it's a calculated risk, the replacement cost of the ancillaries justify the $2500 plus install it would cost me. I didn't check my coolant and as a result, the car overheated, causing the #14 head to crack. How do I know? Before the hoses had flex in the morning, after they were hard as a rock. Even if I get a used engine but with a good #14 head, all I need to do is ensure the car doesn't overheat. Lesson learned.

Does this sound like a fixable issue? If so, what are your thoughts on it and what would it take. Or am I best advised to either replace the engine or to get a full-time car and put the SDL out to pasture as a hobby car?

Casey