Volkswagen Air-Cooled 1970-1981 Repair Guide

Crankcase Reconditioning

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DISASSEMBLING CRANKCASE



See ``Crankcase Disassembly & Assembly'' earlier in this section.

HOT TANK THE CRANKCASE



Using only a hot-tanking solution formulated for aluminum or magnesium alloy, clean the crankcase to remove all sludge, scale, or foreign particles. You may also cold-tank the case, using a strong degreasing solvent, but you will have to use a brush and a lot of elbow grease to get the same results.

After cleaning, blow out all oil passages with compressed air. Remove all old gasket sealing compound from the mating surfaces.

INSPECT THE CRANKCASE



Check the case for cracks using the Zyglo or spot-check method described earlier in this section.

Inspect all sealing or mating surfaces, especially along the crankcase seam, as the crankcase halves are machined in pairs and use no gasket.

Check the tightness of the oil suction pipe. The pipe must be centered over the strainer opening. On 1600 engines, peen over the crankcase where the suction pipe enters the camshaft bearing web.

Check all studs for tightness. Replace any defective studs as mentioned earlier in this section. Check all bearing bores for nicks and scratches. Remove light marks with a file. Deeper scratches and scoring must be removed by align boring the crankshaft bearing bores.

ALIGN BORE THE CRANKCASE





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Fig. Fig. 1: Because of the importance of the fit between both crankcase halves, make sure to have the case align-bored

There are two surfaces on a VW crankcase that take quite a hammering in normal service. One is the main bearing saddles and the other the thrust flange of #1 bearing (at the flywheel end). Because the case is constructed of softer metal than the bearings, it is more malleable. The main bearing saddles are slowly hammered in by the rotation of the heavy crankshaft working against the bearings. This is especially true for an out-of-round crankshaft. The thrust flange of #1 main bearing receives its beating trying to control the end-play of the crankshaft. This beating is more severe in cases of a driver with a heavy clutch foot. Popping the clutch bangs the pressure plate against the clutch disc, against the flywheel, against the crankcase flange, and finally against the thrust flange. All of this hammering leaves its mark on the case, but can be cleaned up by align boring.

Most VW engine rebuilders who want their engines to stay together will align bore the case. This assures proper bearing bore alignment. Then, main bearings with the correct oversize outer diameter (and oversize thrust shoulder on #1) are installed.

Also, as the split crankcase is constructed of light aluminum and magnesium alloy, it is particularly susceptible to warpage due to overheating. Align boring the case will clean up any bearing saddle misalignment due to warpage.

CHECK CONNECTING ROD SIDE CLEARANCE, AND STRAIGHTNESS0.40mm).



Before removing the connecting rods from the crankshaft, check the clearance between the rod and the crank throw using a feeler gauge. Replace any rod exceeding the wear limit. Proper side clearance (also known as end-play or axial play) is .004-.016 in. (0.10

Also, prior to removing the rods from the crankshaft, check them for straightness. This is accomplished easily using an old wrist pin, and sliding the wrist pin through each connecting rod (small end) in succession. Position each rod, in turn, so that as the pin begins to leave one rod, it is entering the next rod. Any binding indicates a scored wrist pin bushing or misaligned (bent) connecting rod. If the wrist pin absolutely will not slide from one adjacent rod to another, then you've got a really bent rod. Be ready for bent rods on any engine which has dropped a valve and damaged a piston.

DISASSEMBLE THE CRANKSHAFT



Number the connecting rods (1 through 4 from the flywheel side) and matchmark their bearing halves. Remove the connecting rod retaining nuts (do not remove the bolts) from the bit end and remove the rods. Slide off the oil thrower (1600 only) and #4 main bearing. Slide off #1 main bearing from the flywheel end. Remove the snapring (circlip) using snapring pliers. #2 main bearing is the split type, each half of which should remain in its respective crankcase half. Using a large gear puller, or an arbor or hydraulic press, remove the distributor drive gear and crankshaft timing gear and spacer. Don't lose the woodruff key(s).

The 1600 engine has two woodruff keys. The 1700, 1800 and 2000 engines have only one.

Finally, slide off #3 main bearing.

INSPECT THE CRANKSHAFT



Clean the crankshaft with solvent. Run all oil holes through with a brass bristle brush. Blow them through with compressed air. Lightly oil the crankshaft to prevent rusting.

Using a micrometer of known accuracy, measure the crankshaft journals for wear. The maximum wear limit for all journals is .0012 in. (0.03mm). Check the micrometer reading against those specifications listed under ``Crankshaft & Connecting Rod Specifications'' which appears earlier in this section.

Check the crankshaft run-out. With main bearing journals #1 and #3 supported on V-blocks and a dial gauge set up perpendicular to the crankshaft, measure the run-out at #2 and #4 main bearing journals. Maximum permissable run-out is .0008 in. (0.02mm).

Inspect the crankshaft journals for scratches, ridges, scoring and nicks. All small nicks and scratches necessitate regrinding of the crankshaft at a machine shop. Journals worn to a taper or slightly out-of-round must also be reground. Standard undersizes are .010, .020, .030 in. (0.25, 0.50, 0.75mm).

INSPECT THE CONNECTING RODS





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Fig. Fig. 2: If it is necessary to balance the crankshaft/connecting rod assembly, metal can be ground off of the connecting rods at the positions shown (arrows)

Check the connecting rods for cracks, bends and burns. Check the rod bolts for damage; replace any rod with a damaged bolt. If possible, take the rods to a machine shop and have them checked for twists and magnafluxed for hidden stress cracks. Also, the rods must be checked for straightness, using the wrist pin method described earlier. If you did not perform this check before removing the rods from the crankshaft, definitely do so before dropping the assembled crankshaft into the case.

Weigh the rods on a gram scale. On 1600 engines, the rods should all weigh within 10 grams (lightest to heaviest); on 1700, 1800 and 2000 engines, within 6 grams. All rods should ideally weigh the same. If not, find the lightest rod and lighten the others to match. Up to 8 grams of metal can be removed from a rod by filing or grinding at the low stress points shown in the illustration.

Check the fit of the wrist pin bushing. At 72 F, the pin should slide through the bushing with only light thumb pressure.

CHECK CONNECTING ROD BEARING (OIL) CLEARANCE



It is always good practice to replace the connecting rod bearings at every teardown. The bearing size is stamped on the back of the inserts. However, if it is desired to reuse the bearings, two methods may be used to determine bearing clearance.

One tedious method is to measure the crankshaft journals using a micrometer to determine what size bearing inserts to use on reassembly (see Crankshaft and Connecting Rod Specifications) to obtain the required 0.00080.0027 in. oil clearance.

Another method of checking bearing clearance is the Plastigage method. This method can only be used on the split-type bearings and not on the ring-type bearings used to support the crankshaft. First, clean all oil from the bearing surface and crankshaft journal being checked. Plastigage is soluble in oil. Then, cut a piece of Plastigage the width of the rod bearing and insert it between the journal and bearing insert.

Do not rotate the rod on the crankshaft.

Tighten the rod cap nuts to 22-25 ft. lbs. Remove the bearing insert and check the thickness of the flattened Plastigage using the Plastigage scale. Journal taper is determined by comparing the width of the Plastigage strip near its ends. To check for journal eccentricity, rotate the crankshaft 90 and retest. After checking all four connecting rod bearings in this manner, remove all traces of Plastigage from the journal and bearing. Oil the crankshaft to prevent rusting.

If the oil clearance is .006 in. (0.15mm) or greater, it will be necessary to have the crankshaft ground to the nearest undersize (.010 in.) and use oversize connecting rod bearings.

CHECK MAIN BEARING (OIL) CLEARANCE



It is also good practice to replace the main bearings at every engine teardown as their replacement cost is minimal compared to the replacement cost of a crankshaft or short block. However, if it becomes necessary to reuse the bearings, you may do so after checking the bearing clearance.

Main bearings #1, 3 and 4 are ring-type bearings that slip over the crankshaft. These bearings cannot be checked using the Plastigage method. Only the split-type #2 main bearing can be checked using Plastigage. However, since this involves bolting together and unbolting the crankcase halves several times, it is not recommended. Therefore, the main bearings are checked using a micrometer. Use the accompanying chart to determine if the bearing (oil) clearance exceeds its wear limit.

Never reuse a bearing that shows signs of wear, scoring or blueing. If the bearing clearance exceeds its wear limit, it will be necessary to regrind the crankshaft to the nearest undersize and use oversize main bearings.

CLEAN AND INSPECT THE CAMSHAFT





Click image to see an enlarged view

Fig. Fig. 3: To compute camshaft lobe lift, subtract measurement B from measurement A angle to the previous measurement (distance B). This will give you camshaft lift. Measure lift for each lobe. If any lobe differs more than .025 in., replace the camshaft.

Degrease the camshaft using solvent. Clean out all oil holes and blow through with compressed air. Visually inspect the cam lobes and bearing journals for excessive wear. The edges of the camshaft lobes should be square. Slight damage can be removed with silicone carbide oilstone. To check for lobe wear not visible to the eye, measure the camshaft diameter from the tip of the lobe to base (distance A) and then mike the diameter of the camshaft at a 90

Check the camshaft for run-out. Place the #1 and #3 journals in V-blocks and rest a dial indicator on #2 journal. Rotate the camshaft and check the reading. Run-out must not exceed 0.0015 in. (0.04mm). Repair is by replacement.

Check the camshaft timing gear rivets for tightness. If any of the gear rivets are loose, or if the gear teeth show a poor contact pattern, replace the camshaft and timing gear assembly. Check the axial (end) play of the timing gear. Place the camshaft in the left crankcase half. The wear limit is .0063 in. (0.16mm). If the end-play is excessive, the thrust shoulder of #3 camshaft bearing is probably worn, necessitating replacement of the cam bearings.

CHECK THE CAMSHAFT BEARINGS



The camshaft bearings are the split-type. #3 camshaft bearing has shoulders on it to control axial play. Since there is no load on the camshaft, the bearings are not normally replaced. However, if the bearings are scored or imbedded with dirt, if the camshaft itself is being replaced, or if the thrust shoulders of #3 bearing are worn (permitting excessive axial play), the bearings should be replaced.

In all cases, clean the bearing saddles and check the oil feed holes for cleanliness. Make sure that the oil holes for the bearing inserts align with those in the crankcase. Coat the bearing surfaces with prelube.

CHECK THE LIFTERS (TAPPETS)



Remove all gum and varnish from the lifters using a toothbrush and carburetor cleaner. The cam following surface of the lifters is slightly convex when new. In service, this surface will wear flat which is OK to reinstall. However, if the cam following surface of the lifter is worn concave, the lifter should be replaced. To check this, place the cam following surface of one lifter against the side of another, using the one lifter as a straightedge. After checking, coat the lifters with oil to prevent rusting.

ASSEMBLE THE CRANKSHAFT



Coat #3 main bearing journal with assembly lubricant. Slide the #3 bearing onto the pulley side of the crankshaft and install the large woodruff key in its recess (the hole in the bearing should be nearest to the flywheel end of the crankshaft). In the meantime, heat both the crankshaft timing gear and distributor drive gears to 176 F in an oil bath. If a hydraulic or an arbor press is available, press on the timing gear, taking care to keep the slot for the woodruff key aligned, the timing marks facing away from the flywheel, and the chamfer in the gear bore facing #3 main bearing journal.Dowel pin holes in the main bearings must locate to the flywheel end of the bearing saddles.


CAUTION
Use protective gloves when handling the heated gears.Be careful not to scratch the crankshaft journals.

Or, if a press is not available, you may drive on the gear using a 2 in. diameter length of pipe and a hammer, taking care to protect the flywheel end of the crankshaft with a piece of wood. The woodruff key must lie flat in its recess. Then, slide on the spacer ring and align it with the woodruff key. On 1600 engines, install the smaller woodruff key. Now, press or drive on the distributor drive gear in the same manner as the crankshaft timing gear. Make sure it seats against the spacer ring. Install the snapring (circlip) using snapring pliers. Take care not to scratch #4 main bearing journal. Prelube main bearings #1 and #4 and slide them on the crankshaft. On 1600 engines, install the oil slinger, concave side out. Make sure crankshaft timing gear and distributor drive gear fit snugly on the crankshaft once they return to room temperature.

Install the bearing inserts for the connecting rods and rod caps by pressing in on bearing ends with both thumbs. Make sure the tangs fit in the notches. Don't press in the middle as the inserts may soil or crack. Prelube the connecting rod bearings and journals. Then, install the connecting rods on the crankshaft, making sure the forge marks are up (as they would be installed in the crankcase [3, 1, 4, 2 from flywheel end]), and the rod and bearing cap matchmarks align. Use new connecting rod nuts. After tightening the nuts, make sure that each rod swings freely 180 on the crankshaft by its own weight. A slight pretension (binding) of the rod on the crankshaft may be relieved by lightly rapping on the flat side of the big end of the rod with a hammer.

If the connecting rod nuts are not of the self-locking type (very rare), peen the nuts into the slot on the rods to lock them in place and prevent the possibility of throwing a rod.

INSTALLING THE CRANKSHAFT AND CAMSHAFT



Pencil mark a line on the edge of each ring-type main bearing to indicate the location of the dowel pin hole. Install the lower half of #2 main bearing in the left side of the crankcase so that the shell fits securely over its dowel pin. Prelube the bearing surface.

Lift the crankshaft by two of the connecting rods and lower the assembly into the left crankcase halve. Make sure the other connecting rods protrude through their corresponding cylinder openings. Then, rotate each ring-type main bearing (#1, then #3, then #4) until the pencil marks made previously align with the center of the bearing bore. As each bearing is aligned with its dowel pin, a distinctive click should be heard and the crankshaft should be felt dropping into position. After each bearing is seated, you should not be able to rock any of the main bearings or the crankshaft in the case. Just to be sure, check the bearing installation by placing the other half of #2 main bearing over the top of its crankshaft journal. If the upper half rocks, the bearing or bearings are not seated properly on their dowels. Then, install the other half of #2 main bearing in the right crankcase halve. Prelube the bearing surface.

Rotate the crankshaft until the timing marks (twin punch marks on two adjacent teeth) on the timing gear point towards the camshaft side of the case. Lubricate and install the lifters. Coat the lifters for the right half of the case with grease to keep them from falling out during assembly. Coat the camshaft journals and bearing surfaces with assembly lubricant. Install the camshaft so that the single timing mark (0) on the camshaft timing gear aligns (lies between) with the two on the crankshaft timing gear. This is critical as it establishes valve timing.

Install the camshaft end plug using oil-resistant sealer. On cars with manual transmission, the hollow end of the plug faces in towards the engine. On cars equipped with automatic or automatic stick shift transmission, the hollow end faces out towards the front of the car to provide clearance for the torque converter drive plate retaining bolts.

The timing gear mesh is correct if the camshaft does not lift from its bearings when the crankshaft is rotated backwards (opposite normal direction of rotation).

CHECK TIMING GEAR BACKLASH



Mount a dial indicator to the crankcase with its stem resting on a tooth of the camshaft gear. Rotate the gear until all slack is removed, and zero the indicator. Then, rotate the gear in the opposite direction until all slack is removed and record gear backlash. The reading should be between .000 and .002 in. (0.00 and 0.05mm).

ASSEMBLING THE CRANKCASE





Click image to see an enlarged view

Fig. Fig. 4: Before assembling the two crankcase halves, make certain to install new crankcase stud seals

See ``Crankcase Disassembly & Assembly'' earlier in this section. Use the following installation notes;

  1. Make sure all bearing surfaces are prelubed.
  2.  
  3. Always install new crankcase stud seals.
  4.  
  5. Apply only non-hardening oil resistant sealer to all crankcase mating surfaces.
  6.  
  7. Always use new case nuts. Self-sealing nuts must be installed with the red coated side down.
  8.  
  9. All small crankcase retaining nuts are first torqued to 10 ft. lbs., then 14 ft. lbs. All large crankcase retaining nuts are torqued to 20 ft. lbs., then 25 ft. lbs. (except self-sealing large nuts [red plastic insert], which are torqued to a single figure of 18 ft. lbs.). Use a crisscross torque sequence. On 1700, 1800 and 2000 engines, you will have to keep the long case bolt heads from turning.
  10.  
  11. While assembling the crankcase halves, always rotate the crankshaft periodically to check for binding. If any binding occurs, immediately disassemble and investigate the case. Usually, a main bearing has come off its dowel pin, or maybe you forgot to align bore that warped crankcase.
  12.  

CHECK CRANKSHAFT END-PLAY0.13mm)





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Fig. Fig. 5: Cross-sectional view of the flywheel, crankshaft, oil seal and related components used on 1600cc engines

After assembling the case, crankshaft end-play can be checked. End-play is controlled by the thickness of 3 shims located between the flywheel and #1 main bearing flange. End-play is checked with the flywheel installed as follows. Attach a dial indicator to the crankcase with the stem positioned on the face of the flywheel. Move the flywheel in and out and check the reading. End-play should be between .003-.005 in. (0.07 The wear limit is .006 in. (0.15mm).

To adjust end-play, remove the flywheel and reinstall, this time using only two shims. Remeasure the end-play. The difference between the second reading and the .003-.005 in. figure is the required thickness of the third shim. Shims come in the following sizes:



0.24mm - .0095 in.
 
0.30mm - .0118 in.
 
0.32mm - .0126 in.
 
0.34mm - .0134 in.
 
0.36mm - .0142 in.
 
0.38mm - .0150 in. (1700, 1800 and 2000 only)
 

 
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