Contents: Inspection 🠛 Assembly 🠛
Inspection
1. Before beginning inspection, clean the piston/connecting rod assemblies and remove the piston rings.
2. Carefully release the rings and remove them from the piston head. Use two or three old feeler gauges to prevent the rings from jumping into already empty grooves (see illustration).
15.2. Using an old feeler gauge, remove the piston rings.
3. Clean off the main carbon deposits from the piston head. Then clean it with a wire brush or fine sandpaper.
4. Remove carbon deposits from the piston ring grooves using a piece of an old ring (break the ring in half, working carefully to avoid cutting your fingers). Be careful not to remove any metal along with the carbon deposits and not to scratch the walls of the grooves.
5. After removing the carbon deposits, clean the piston/connecting rod assembly with kerosene or a suitable solvent and dry it thoroughly. Make sure that the return oil holes in the ring grooves are not clogged.
6. If the pistons and cylinder walls are not damaged or worn, and if the cylinder block does not require regrinding, the old pistons can be installed. Normal wear of the piston is manifested by uniform vertical wear of its axial pressure surfaces and a slight play of the upper ring in the groove. When assembling the engine, the piston rings must be replaced.
7. Carefully inspect each piston for cracks in the skirt, around the piston pin holes and between the ring grooves.
8. Inspect the piston skirt for damage and the piston head for holes or edge burns. If the skirt is scratched or nicked, or the piston crown is pitted or burned, the engine may have been overheating and/or misfiring (the fuel mixture ratio or injection/ignition timing were incorrectly adjusted). Check the cooling and lubrication systems thoroughly. Burnt spots on the sides of the pistons indicate that a gas breakthrough has occurred. If any of the above damages are found, identify the causes and eliminate them, otherwise the damage will occur again. On gasoline engines, the cause could be an intake air leak, improper fuel/air mixture adjustment, or incorrect spark advance. On diesel engines - incorrect fuel pump injection timing or a defective injector.
9. Piston corrosion indicates that coolant has leaked into the combustion chamber and/or crankcase. Identify the cause of the leak and fix it.
10. If new rings are being installed on old pistons, measure the gap between the ring and the groove wall by inserting the new ring into the groove and measuring the gap with a feeler gauge. Check the clearance in three or four places around each groove. There are no specific data provided by the manufacturer, but if the measured clearance is greater than 0.10 mm, new pistons will be required. If the new ring fits into the groove too tightly, it is most likely due to dirt remaining in the groove.
15.10. Measure the gap between the ring and the groove wall.
11. Check the clearance between the pistons and the cylinder/liner walls by measuring the inner diameter of the liner or cylinder (see Chapter 14) and piston diameter. Measure the piston diameter on the skirt perpendicular to the piston pin (see illustrations).
15.11. Measure the piston out-of-roundness.
Subtract the piston diameter from the cylinder/liner diameter to get the clearance. On D- and F-series engines, if the diameter is greater than the data given in the Specifications, the cylinder block must be bored and new pistons and rings must be installed. On C- and E-series engines, new pistons and liners are supplied in matched pairs.
12. Check the installation of the piston pin by rotating the piston and connecting rod in opposite directions. If there is play, this indicates excessive wear. If pistons or connecting rods need replacing, have this work carried out by a Renault dealer or an engine rebuilder. (In the case of the F7P 16-valve engine, the piston pins are secured with circlips, so the pistons and connecting rods can be separated without any problem. Note the orientation of the piston relative to the connecting rod, and use new locking rings when assembling).
13. Before installing the ring on the piston, check the gaps of the cuts (see illustrations).
15.13. Measure the piston ring gap.
There is no data specified by the manufacturer, but the following values can be used as a guide: 0.50 mm for compression rings, and a little more for oil scraper rings. The clearance in Renault rings cannot be adjusted.
Assembly
14. Install new rings on the pistons (see illustrations).
15.14. Designation of piston rings on the E-series engine.
Note that the second compression ring is tapered. Both compression rings must be installed with the word "TOP" facing up (see illustration).
15. Space the ring cut gaps evenly at 120° apart.
16. Please note that if new piston and liner assemblies are received, each piston is matched to its corresponding liner and they must not be mixed up.