1. If there is a suspicion that coolant has entered the crankcase, then check the tightness of the cylinder block on a special stand. To do this, after plugging the holes in the cooling jacket of the cylinder block, inject water at room temperature into it at a pressure of 0.3 MPa (3 kgf/cm2). Within two minutes, there should be no leakage of water from the cylinder block.
2. If oil gets into the coolant, then without completely disassembling the engine, check for cracks in the cylinder block in the areas of the oil channels. To do this, drain the coolant from the cooling system, remove the cylinder head, fill the cooling jacket of the cylinder block with water and supply compressed air to the vertical oil channel of the cylinder block. If air bubbles appear in the water filling the cooling jacket, replace the cylinder block.