BMW 11251261926 Mahle Piston

Taken off the cylinder head and sump as described earlier in this article. Rotate the crankshaft clockwise with the aid of a spanner to the nut of the pulley such that the big-end of the piston or the connecting rod is at the lowermost level. Connecting rods and big-end caps are identified at points opposite to each other, and all series start at the front of the engine with no. 1. Remove Bieg-end nuts, rotate the cap and pull the piston /connecting rod assembly out from above the block. If there is a sever wear ridge at the top of the cylinder bore, it is advisable to scrape it away before pulling the piston, in order to prevent damaging the piston rings. Before final assembly, the bearing shells must be removed from the cap and rod; to help distinguish between them, use masking or have a spirit marker define on the rear of the bearing shells The essential differentiation is critical if reproducing the original shells. The gudgeon pin can be pulled out after take out the circlips and pushing the pin with fingers only but be careful with the position of the rod oil hole to the arrow on the piston crown for reconnection. Eliminate the first set of big-end bolts and nuts and acquire a new set of them. The piston rings are rather fragile, and open too wide during removal, they may break; previous to removing the rings place two or three old feeler blades or strips of tin behind each ring at proper intervals. Rotate the rings counter clockwise to remove them from the top of the piston so that the feeler blades stop a lower ring from falling lower as it is pulled out.

Assemble the no. 1 piston to the connecting rod, ensuring the arrow on the piston crown faces forwards and the oil hole below the small end bush on the rod aligns in the same direction, with sequence numbers on the cap and rod facing to the right when viewed from the front of the engine. Push the gudgeon pin into position using finger pressure and insert two new cir clips. Install the piston rings by reversing the removal process, noting the fitting sequence and ring cross sections. Stagger the piston ring end gaps at equal points of a circle. Insert the bearing shell into the connecting rod, apply oil liberally to the bearing and piston rings, and smear some up and down the cylinder bore before fitting a piston ring compressor. Carefully insert the connecting rod into the cylinder bore to avoid scratching the surfaces, ensuring the compressor is squarely on the top of the cylinder block and the piston rings are well compressed but not tight. Use a wooden shaft of a hammer to tap the piston/rod assembly down the bore, then remove the ring compressor. Turn the crankshaft so the number 1 big-end journal is at its lowest point of travel and pull down the connecting rod onto it, ensuring the bearing shell remains in place. Fit the shell to the big-end cap, oil it, and install it, making sure the numbers on the cap and rod are adjacent while rechecking that the piston crown arrow faces the front of the engine. Install the big-end bolts and nuts, tightening them to the specified torque with the narrower diameter of the nut nearest the big-end cap. Repeat these operations for the remaining three piston/connecting rod assemblies.