As mentioned, a blow-by test is done without any tools.

With the engine running, remove the oil fill cap on the cam cover. Does the cap do a dance, or is blown into the next county?

A dance is normal. If you can't find it, that indicates too much blow-by and the engine needs work.

__________________
83 SD

84 CD

A couple other things I have learn to check are testing the windshield seals with my thumb nail to see if they are hard and soon to be replaced, and also taking off the oil cap and checking the first lobe of the cam.

The first cam is close enough that you can feel for a flat spot, or see if the cam is scored. Mercedes changed the cam from ductile iron to white iron about 1980, and I have come across a couple of engines with the ductile cam scored, and a couple of white iron cams with flat spots on the lobes.

I've also learned to open the sun roof and check to see if inside the opening is rusty.

W.

Bought the car. front window seal is gone, but no rust in floor pans, I didn't check the lobes but the engine ran as well as one could, no blowby and no excessive smoke, idled smoothly, was pretty quiet, and the power was very good. Also, no sunroof. Refer to new thread: New purchase: 1980 300SD

__________________
Current: 1975 450SEL, 83 300D, 88 Yugo GVX, 90 300D OM603 swap, 91 F150 4.6 4v swap, 93 190E Sportline LE 3.0L M104 swap, 93 190E Sportline LE Megasquirt, 03 Sprinter, 06 E500 4Matic wagon.