Hi Folks!

My Explorer ran out of fuel on a 10mile road trip at about 45mph. After hearing a strange sound I immediately pulled the clutch and the engine stopped. After refueling I noticed that compression is lower than it was before but still present. I am worried that the piston seized as the engine doesn't start any more.

Any ideas what I can look at before I start dismantling the whole engine?

Thanks!
Felix

Unfortunately, it likely seized.

Start by draining the coolant and removing the head to inspect the cylinder wall.  

It's possible to remove the cylinder and piston as a unit without removing the engine from the chassis.  Of course, you must first remove the piston pin. 

In case cylinder is seized what measure would be more feasable and /or economic: Replacing cylinder and piston or overhaul cylinder?

After a seizure, the piston probably must be replaced.  If the seizure was very light, it's sometimes possible to sand a damaged piston smooth again.  But if there has been any aluminum transferred to the cylinder, sanding is not advisable.  Furthermore, if any rearranged aluminum has impinged on the ring lands, the piston must be replaced.

If the cylinder damage is just aluminum transfer, it's possible to remove the aluminum with hydrochloric (aka muriatic) acid.  But, if any peeling of the plating has occurred, the cylinder must be re-plated.  Sometimes imperfections in the cylinder plating are tolerated in areas above the ring travel or below the piston travel.

Note that Nikasil plating is very hard, and a diamond hone must be used.  A standard cylinder hone for iron won't work.   

It's probably not possible to determine the extent of seizure damage from photographs.  If in doubt, a local specialist should be consulted.

But finding OSSA parts is not easy either. ☹️

Edited September 7, 2025Sep 7 by konrad
Upon consultation with an industry expert, I revised my initial post somewhat.