I finally got back around to working on my 1981 300SD 126 after finishing "other" projects. Starts as soon as engine turns over. Very rough idle, smooth at about 2,000rpm. I have one cylinder (#2) not firing---so compression check on all cylinders (1 thru 5): 300psi, 60psi, 310psi, 310 psi, 330psi. Check #2 again just to make sure. 60psi. Not good. I do leakdown test---#2, set value at 30psi, leaks 95%. I apply 100 psi to listen for air---no air from intake or exhaust manifold---valves good---I do hear air from where chain comes out of crankcase---not good. Sounds like piston and or ring/s. 193,000 miles on engine. I'm trying to decide whether to take this engine apart and just replace the one piston/rings (maybe even use used piston/rings)---lots of work, but cheap----or go with a remanufactured short block at about 3K---or long block at about 6K. I would like to think "bad head gasket"----but just does not seem to fit test results. Only thing that bothers me is why would just ONE piston/rings "go bad"? You guys help me make up my mind! I will be making the 126 one of my daily drivers.

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K. Weimer
300SD (1)
300D (5) [Plus 1 parts]
300SEL 4.5 (2)
280SE (4)
280 (2)
250 (1)
250SE (1)
240D (7) [Plus 1 parts]
220D (11) [Plus 3 parts]
200D (2) [Plus 1 parts]
180c (with sunroof)

1995 Nissan UD1800 rollback
"If I can't fix it, it don't get fixed"