Standard Procedure-Piston Ring Fitting

Before reinstalling used rings or installing new rings, the ring clearances must be checked.

1. Wipe the cylinder bore clean.
2. Insert the ring in the cylinder bore.
   NOTE: The ring gap measurement must be made with the ring positioned at least 12 mm (0.50 inch.) from bottom of cylinder bore.
3. Using a piston, to ensure that the ring is squared in the cylinder bore, slide the ring downward into the cylinder.
4. Using a feeler gauge check the ring end gap (Fig 1). Replace any rings not within specification.
   Fig 1: Measuring Ring End Gap

   Courtesy of DAIMLERCHRYSLER CORP.
   NOTE: Make sure the piston ring grooves are clean and free of nicks and burrs.
5. Measure the ring side clearance as shown (Fig 2)make sure the feeler gauge fits snugly between the ring land and the ring. Replace any ring not within specification.
   Fig 2: Measuring Piston Ring Side Clearance

   Courtesy of DAIMLERCHRYSLER CORP.
6. Rotate the ring around the piston, the ring must rotate in the groove with out binding.
   PISTON RING SPECIFICATION CHART
   
   

   Ring Position	Groove Clearance	Maximum Clearance
   Upper Ring	.051-.094mm (0.0020- .0037 in.)	0.11mm (0.004 in.)
   Intermediate Ring	0.04-0.08mm (0.0016-0.0031 in.)	0.10mm (0.004 in.)
   Oil Control Ring (Steel Rails)	.019-.229mm (.0007-.0090 in.)	.25mm (0.010 in.)
   Ring Position	Ring Gap	Wear Limit
   Upper Ring	0.20-0.36mm (0.0079-0.0142 in.)	0.43mm (0.0017 in.)
   Intermediate Ring	0.37-0.63mm (0.0146-0.0249 in.)	0.74mm (0.029 in.)
   Oil Control Ring (Steel Rail)	0.025-0.76mm (0.0099- 0.03 in.)	1.55mm (0.061 in.)

7. The No. 1 and No. 2 piston rings have a different cross section. Ensure No. 2 ring is installed with manufacturers I.D. mark (Dot) facing up, towards top of the piston.
   NOTE: Piston rings are installed in the following order:

   • Oil ring expander.
   • Upper oil ring side rail.
   • Lower oil ring side rail.
   • No. 2 Intermediate piston ring. 
   • No. 1 Upper piston ring. 
8. Install the oil ring expander.
9. Install upper side rail (Fig 3) by placing one end between the piston ring groove and the expander ring. Hold end firmly and press down the portion to be installed until side rail is in position. Repeat this step for the lower side rail.
   Fig 3: Installing Side Rail

   Courtesy of DAIMLERCHRYSLER CORP.
10. Install No. 2 intermediate piston ring using a piston ring installer (Fig 4).
    Fig 4: Installing Upper And Intermediate Rings

    Courtesy of DAIMLERCHRYSLER CORP.
11. Install No. 1 upper piston ring using a piston ring installer (Fig 4).
12. Position piston ring end gaps as shown in (Fig 5). It is important that expander ring gap is at least 45° from the side rail gaps, but not on the piston pin center or on the thrust direction.
    Fig 5: Identifying Piston Ring End Gap Position

    Courtesy of DAIMLERCHRYSLER CORP.