Looking at a 82 300D when I started it up tons of white smoke came out of exhaust and car was shaking some. Took for a test drive and it shifted fine. Returned and let it sit for 30 minutes and started again a puff off back smoke was then followed by a steady stream of white smoke - white smoke on 2nd startup was not an intense. I have seen this in W126 350SDs before and it is always injectors or even glow plug related. However I called mechanic and he said watch out for cracked head. He said exhaust will smell sweet if it is a bad head since coolant would be burning with diesel also he said this would account for shaking since mixing coolant and diesel at startup is not good Anyone else had these symptoms? Is there any other way to check for a bad head? Unfortunately I cannot go on long test drive again.