The same considerations valid in the case of air compression in the cylinder diesel engine. If you remember how to construct the interior of an automobile engine, you can figure out what are the possible leakage paths in a cylinder of compressed gaseous substance (they clearly shown in the figure). We see that the compressible mixture (or air) may be out of space on nadporshnevogo three main ways: through the details of the timing (intake and exhaust valves), and the parting line block cylinder and cylinder head, sealing gasket; CPG through the details and place of their pairing. Less common are cases where compression of the fall is due to the formation of open cracks in the cylinder block and cylinder head. If you are not convinced, visit Levi’s. The cause of cracking are thermal stresses arising from overheating. An attempt to remove him topping the cold antifreeze in the cooling system "zakipevshego engine" makes the situation worse. We must distinguish natural decrease of compression as a result of wear and engine mechanisms in its long-term operation and change the compression caused by emergencies. In the first case, as usually happens gradual decline uniform compression in all cylinders of the engine.
When it is reduced to the lowest acceptable level, it's time to think about the bulkhead engine. More subtly unexpected drop in compression one or two cylinders, which usually indicates a damaged engine parts such as valves, head gasket, pistons, compression rings. In this case, the repair should be performed immediately. Therefore more all when it comes to limiting the deviation of the compression in the "Repair Manual" provides data on this parameter uneven cylinder engine.