- Mover -

I've performed a leakdown test on my previous non Mercedes car several times.

It had a manual transmission; keeping the engine from spinning when applying pressure to the cylinder was not a big deal even if the piston wasn't at TDC completely. All I had to do is put it in top gear (6th in this case) and make sure the wheels were choked. The car wouldn't move and performing a leakdown test was easy.

I've never performed one on a car with an automatic transmission.

What steps do I need to take to perform a leakdown on my 2010 E550 (M273 engine) ?

- Mover -

More specifically, how do I lock the engine from spinning ?

( I know how to perform a leakdown test )

bbirdwell

Drop the plate under the flywheel and use a pry bar to lock the flywheel in place. May take a bit of work to figure out how to keep the bar in place but it it do-able.

Alternatively, place a breaker bar and socket on the harmonic balancer bolt on the end of the crankshaft. You're not going to be applying enough torque to worry about loosening it.

- Mover -

Are you saying for someone to hold the breaker bar while applying 100psi into the cylinder ? With that kind of pressure, isn't it going to rip the breaker bar out of their hands ?

With the manual transmission cars that I've done, it was just a matter of putting it in the highest gear and choking the wheels.