See Figures 1, 2, 3, 4 and 5
These procedures may be performed with the engine in the vehicle. If additional overhaul work is to be performed, it will be easier if the engine is removed and mounted on an engine stand. Most stands allow the block to be rotated, giving easy access to both the top and bottom. These procedures require certain hand tools which may not be in your tool box. A cylinder ridge reamer, a numbered punch set, piston ring expander, snapring tools and piston installation tool (ring compressor) are all necessary for correct piston and rod repair. These tools are commonly available from retail tool suppliers; you may be able to rent them from larger automotive supply houses.
- If the engine is still in the vehicle, the pistons and rods can be removed without removing the crankshaft. Remove the cylinder head and oil pan.
- Turn the crankshaft until the piston to be removed is at the bottom of its travel.
- Matchmark the connecting rod and cap on the same side to indicate the cylinder number and so they can be reassembled the same way. Remove the connecting rod cap and bearing insert.
- Mark the top of the piston to indicate the cylinder number and an arrow pointing towards the timing belt. This will allow you to make sure the pistons are installed in their original cylinder and facing the correct direction.
- Place a rag down the cylinder bore on the head of the piston to be removed. Remove the cylinder top ridge and carbon deposits with a ridge reamer, following the instructions of the reamer's manufacturer.
Do not cut too deeply or remove more than 0.15mm (0.006 inches) from the ring travel area when removing the ridge.
- Remove the rag and metal shavings from the cylinder bore. The cylinder bore must be free of metal shavings before attempting remove the piston.
- Use a short pieces of hose to cover the bolt threads. This protects the bolt, the crankshaft and the cylinder walls during removal. Push the connecting rod up the bore slightly and remove the upper bearing insert.
- Push the connecting rod and piston assembly up and out of the cylinder with a hammer handle or wooden dowel.
- Wipe any dirt or oil from the connecting rod bearing saddle and rod cap. Install the bearing inserts (if to be reused) in the connecting rod and cap to protect them from damage. Install cap, then finger-tighten the rod bolts.
- If necessary, remove the rest of the rod and piston assemblies.
CLEANING AND INSPECTION
See Figures 6, 7, 8, 9, 10 and 11Pistons
After removing the piston and rod assemblies from the engine, clamp the connecting rod into a vise with the lower edge of the piston just resting on the vise jaws. Use a ring expanding tool and remove the piston rings from the piston. Clean the top of the piston with a dull scraper or wire wheel. Use care not to gouge the piston when removing the carbon deposits. Clean the ring grooves using an appropriate groove cleaning tool. A broken piston ring can be used if a groove cleaner is not available. Once again, use care not to cut too deeply or gouge the ring seat. After all the pistons have had the rings removed and grooves cleaned, soak them in safe solvent. Do not use a caustic solvent on the pistons.
After the pistons have been cleaned and wiped dry inspect them for scuffing, scoring, cracks, pitting or excessive ring groove wear. If wear is evident, the piston must be replaced. Hold the connecting rod in one hand, grasp the piston in the other hand and twist the piston and rod in opposite directions. If excessive clearance (looseness) is detected, the piston pin, connecting rod bushing or piston and rod may require replacement. An automotive machine shop can perform this job for you. If you are not sure of the extent of wear present or what component needs replacing, take the assemblies to the machine shop and have them checked.
Measure, or have the machine shop measure the piston with a micrometer. Turn the piston upside down and take a measurement at a point 5 / 8 in. (16mm) below the lower edge of the piston, 90 degrees away from the piston pin holes. Measure the cylinder bore at three places to see if the cylinder is still round and straight. Measurements should be taken at a number of places in each cylinder (at the top, middle and bottom at two points at each location) that is at a point 90 degrees from the crankshaft, as well as a point parallel to the crankshaft. The difference between the greatest measurement of the cylinder wall and the diameter measurement of the piston is the piston-to-cylinder wall clearance. If the difference is greater than 0.0028 inches (0.03mm), the clearance is too great and the cylinders should be machined to accept the next oversize piston. If any one cylinder is more than 0.0016 inches (0.04mm) out of round, all cylinders should be bored out to the next oversize. The machine shop or dealer parts department can provide information about what piston sizes are available.
The connecting rods must be free from wear, cracking and bending. Visually examine the rod, particularly at its upper and lower ends. Look for any sign of metal stretching or wear. The piston pin should fit cleanly and tightly through the upper end, allowing no side-play wobble. The bottom end should also be an exact 1 / 2 circle, with no deformity of shape. The bolts must be parallel.
The rods may be taken to a machine shop for exact measurement of twist or bend. This is easier and cheaper than purchasing a seldom used rod-alignment tool.
See Figures 12 and 13
Most inspection and service work on the cylinder block should be handled by a machinist or professional engine rebuilding shop. Included in this work are bearing alignment checks, line boring, deck resurfacing, hot-tanking and cylinder block boring. Any or all of this work requires that the block be completely stripped of all components and transported to the shop. A block that has been checked and properly serviced will last much longer than one whose owner cut corners during a repair.
Cylinder de-glazing (honing) can be performed by the owner/mechanic who is careful and takes time to be accurate. The cylinder bores become glazed during normal operation of the engine as the rings ride up and down constantly. This shiny glaze must be removed in order for a new set of piston rings to seat properly.
Cylinder hones are available at most auto tool stores and parts jobbers. Install the hone into the chuck of a variable speed drill (preferred in place of a constant speed drill). With the piston, rod and crankshaft assemblies removed from the block, insert the hone into the cylinder. If the crankshaft is not being removed from the block, cover it completely with oil soaked rags to prevent grit from collecting on it.
Make sure the drill and hone are kept square to the cylinder bore during the entire honing procedure.
Start the drill and move the hone up and down in the cylinder at a rate which will produce approximately a 60 degree cross-hatch pattern. DO NOT extend the hone below the bottom of the cylinder bore. After the crosshatched pattern is established, remove the hone.
Wash the cylinder with a solution of detergent and water to remove the honing and cylinder grit. Wipe the bores out several times with a clean rag soaked in fresh engine oil. If applicable, carefully remove the rags from the crankshaft and check closely to see that NO grit has found its way onto the crankshaft.
PISTON PIN REPLACEMENT
Make sure the piston, connecting rod and rod cap are marked with the number of the cylinder the assembly came from. Remove the piston from the connecting rod by inserting a small blunt drift in the small cutout provided on each side of the piston at the piston pin ends. Pry upward on the circlip to compress, and remove both circlips. Use a blunt drift slightly smaller than the diameter of the piston pin to gently drive the pin out. If resistance is encountered when removing the piston pin, submerge the pistons in hot water (140°F/60°C) to expand the metal, then carefully drive the pin out. Inspect the piston pin, connecting rod bushing and piston pin bore for galling, scoring or excessive wear. If wear is evident, consult the machine shop for advice as to what repair will be necessary.
PISTON RING REPLACEMENT
See Figures 14 and 15
After the cylinder bore has been finish honed, or determined to be in satisfactory condition, ring end gap clearance can be checked. Compress one of the piston rings to be used into the cylinder. Press the ring down the bore to a point about 1 in. (25mm) below the top with an inverted piston. Measure the distance between the two ends (ring gap) of the ring with feeler gauges and compare to specifications. Carefully pull the ring from the cylinder, and if necessary, file the ends with a fine file to gain required clearance. Roll the outside of the ring around the piston groove it will be installed in to check for burrs or unremoved carbon deposits. Dress the groove with a fine file if necessary. Hold the ring in the groove and measure between top of ring and groove with a set of feeler gauges to check side clearance. If clearance is excessive, a new piston may be required. Consult the machine shop for their advice.
Install the piston rings on the piston starting with the lower oil control ring. Always refer to the ring manufacturer's instruction sheet for guidance. Be sure, when installing a three piece expander type oil ring, that the ends of the expander are butted together and do not overlap. Hold the butted edges together and install the lower rail first. Install with the ring gap about 19mm ( 3 / 4 inches) away from the butted point of the expander. Install the upper rail on the opposite side, 3/4 away from the butted point of the expander. Use a ring expander and install the compression rings, lower ring first. Most compression rings will have a top mark of some kind, be sure the mark is facing up.
Before installing the piston ring compressor, be sure the piston ring gaps are staggered 60 degrees apart from each other. The gaps should be at three equal spacings, never in a straight line. Avoid installing the rings with their ends in line with the piston pin bosses and the thrust direction. Always refer to the ring manufacturer's instruction sheet for guidance.
ROD BEARING REPLACEMENT
See Figure 16
Connecting rod bearings on all engines consist of two halves or shells which are not interchangeable in the rod and cap. When the shells are in position, the ends extend slightly beyond the rod and cap surfaces so that when the bolts are tightened, the shells will be clamped tightly in place. This insures a positive seating and prevents turning. A small tang holds the shells in place within the cap and rod housings.
The ends of the bearing shells must never be filed flush with the mating surface of the rod or cap.
If a rod becomes noisy or is worn so that its clearance on the crankshaft is out of specification, a new bearing of the correct undersize must be selected and installed. There is no provision for adjustment. Under no circumstances should the rod end or cap be filed to compensate for wear, nor should shims of any type be used.
Inspect the rod bearings while the rods are out of the engine. If the shells are scored or show flaking they should be replaced. Measuring the clearance between the connecting rod bearings and the crankshaft (oil clearance) is done with a plastic measuring material such as Plastigage® or similar product.
- Remove the rod cap with the bearing shell. Completely clean the cap, bearing shells and the journal on the crankshaft. Blow any oil from the oil hole in the crank. The plastic measuring material is soluble in oil and will begin to dissolve if the area is not totally free of oil.
Place a piece of the measuring material lengthwise along the bottom center of the lower bearing shell. Install the cap and shell. Tighten to:
- 37 ft. lbs. (50 Nm) on 5-cylinder engines without stretch-type bolts.
- 33 ft. lbs. (45 Nm) on 4-cylinder engines (gas and diesel) without stretch-type bolts.
- 22 ft. lbs. (30 Nm) on all engines with stretch-type bolts.
Do not turn the crankshaft with the measuring material installed.
- Remove the bearing cap with the shell. The flattened plastic material will be found sticking to either the bearing shell or the crank journal. DO NOT remove it yet.
- Use the scale printed on the packaging for the measuring material to measure the flattened plastic at its widest point. The number within the scale which is closest to the width of the plastic indicates the bearing clearance in thousandths of an inch.
- Check the specifications chart for the proper clearance. If there is any measurement approaching the maximum acceptable value, replace the bearing.
DIESEL PISTON PROJECTION
See Figure 17
On diesel engines, the top of the piston actually protrudes above the top of the cylinder deck when the piston is at TDC. This piston "pop-up" must be measured before installing the cylinder head.
A spacer (VW385/17) and bar with dial indicator (VW 382/7) are necessary, and should be set up as shown in the illustration to measure the maximum amount of piston projection above the deck height. To measure the piston height of particular cylinder, bring the piston up so that the top of the piston is dead flush with the surface of the block. Mount the indicator and spacer onto the cylinder deck. Slide the indicator over and zero the indicator stylus on the top of the piston. Now, very slowly rotate the crankshaft until a deflection is read on the indicator. This can be a very tricky reading, because you have to catch the indicator deflection before the piston starts on the downward travel. Take several readings per cylinder to get an average.
After piston height has been determined, a head gasket of suitable thickness must be used. Head gasket thickness is coded by the number of notches located on the edge and by a part number on the gasket near the notches. If the same parts are being used over again, install a new gasket with the same number of notches as the one removed. The following shows the piston height with its corresponding notch number:
1979-84 Rabbit and Jetta
1985-86 Golf and Jetta (Mechanical Lifters)
1985-89 Golf and Jetta (Hydraulic Lifters)
See Figures 18, 19, 20 and 21
Connecting rod bolts with a conical head and six notches on the nuts are stretch-type bolts and cannot be reused. The bolts must be replaced when the connecting rod is disassembled.
- After the piston and connecting rod have been cleaned, inspected and prepared for installation, use new oil to lubricate the piston, rings, cylinder walls and crankshaft journal.
- Lubricate the upper rod bearing saddle and fit the new bearing into place.
- Install a piston ring compressor over the rings and top of the piston. Before tightening the ring compressor, be sure the ring gaps are staggered 60 degrees apart.
- Lower the piston and rod assembly into the cylinder bore with the arrow on the piston head facing the front of the engine. When the ring compressor contacts the top of the engine block, check to make sure the connecting rod is properly aligned with the crankshaft journal. Use a wooden hammer handle to gently tap the piston into the bore.
If unusual resistance is encountered when starting the piston into the cylinder bore, the piston may be cocked or a ring has slipped out of the compressor and is caught at the top of the cylinder. Remove the piston and reinstall compressor. Forcing the piston in will break the rings.
- Carefully guide the connecting rod down the cylinder bore and over the crankshaft journal, taking care not to score the wall or crankshaft.
- Fit the lower bearing insert into the bearing cap. Lubricate the insert and mount the cap on the rod with matchmarks aligned.
Install rod nuts and torque carefully to the following:
- 37 ft. lbs. (50 Nm) on 5-cylinder engines without stretch-type bolts.
- 33 ft. lbs. (45 Nm) on 4-cylinder engines (gas and diesel) without stretch-type bolts.
- 22 ft. lbs. (30 Nm), then an additional 1 / 4 turn on all engines with stretch-type bolts.
- Lubricate the cylinder wall and turn the crankshaft to make sure the rod bearing is properly installed. If the crankshaft will not turn, remove the bearing cap and check bearing alignment.
- If removed, install the oil spray nozzle. Apply a thread locking compound to the threads, then tighten the bolt to 7 ft. lbs. (10 Nm).
- Install remaining piston and rod assemblies. Turn the crankshaft each time so the crank journal of the piston being installed is at the bottom of travel.