BMW 11257506222 Mahle Piston

Before doing away with the piston and connecting rod Assemblies the cylinder head, oil pan, oil pan baffle plate and oil pump has to be dismantled. Carry out a fingernail scrape at about ¼ inch from the top of each cylinder where there is usually a ridge; where the ridge has resulted from carbon deposits or where worn, it must be smoothed with a ridge reamer so that there is no breaking of the piston. Once the crankshaft ridges have been phased out you can turn the engine in a way that the crankshaft is on top. Inspection of connecting rod end play is done with feeler gauges with end play being between 0.005 to 0.015 inch as the service limit. On the connecting rods and caps paint or use marker so that they will not be mixed up again, then turn the connecting rod cap bolts sparingly. Lift out the first connecting rod cap and bearing insert without allowing the insert to fall, expel the connecting rod/piston assembly from through the top of the engine. Do the same for all the other cylinders, ensure that all the caps and inserts are replaced to avoid damage. Pistons and connecting rods are also now prepared for inspection and if necessary for overhaul. When fitting new piston rings always measure the end gaps as it is important to know the piston ring side clearance. Sort the piston/connecting rod assemblies on the bench and new ring sets to be fitted together as a set. Fit the top ring into the first cylinder, align it to the walls and use the feeler gauges to check the end gap and correct it if required. The first step being installation of the oil control ring, middle and on top ring with respect to the orientation. Before installation of this product, the cylinder walls must be clean, edges of the cylinder machined and the crank shaft fixed. Remove any dirt on the bearing surfaces and unbending the top and bottom bearing insert with no lubrication used. Place the gaps of the piston rings evenly at an interval of 120 degree, lubricate the piston/rings and then use a compressor for the rings to be fitted. Using Plastigage check connecting rod bearing oil clearance make sure that the size and the condition of the bearing is clean. Remove any excess Plastigage by scraping it off and apply grease or assembly lube then install the rod cap with new bolts and tighten to recommended torque figure. As for all assemblies, be sure you clean and ensure the correct orientation. Last of all, rotate the crankshaft and look for sign of binding and measure the connecting rod end play if the figure is outside of acceptable range a change will be made to it.

The forged steel connecting rods have replaceable split-shell bearings at the crankshaft end to crank and piston pin end has solid bushing.Weight classes are can be seen with different colors such as blue, red and green. Pistons contain three rings, two in form of upper compression rings and one lower one-piece oil scraper ring; piston pins float full and use circlips for retention. Also, the use of graphite coating is incorporated in piston skirts to reduce friction and noise.

The weight classes are indicated by a color code system.