Valve adjustment

AZDANNO04

MEMBER
1998 NISSAN SENTRA
1.6L
4 CYL
2WD
AUTOMATIC
229,700 MILES

The noise is coming from underneath the valve cover. I just replaced the upper tensioner. I don't recall evening seeing the upper chain guide after seeing a an example in the book for the Nissan Sentra. So either the chain guides are worn the valves need adjustment. I was told that I need a feeler gauge and something about different shims to take place for areas that would need adjustment. I know when I last looked at the timing components everything looked intact the teeth weren't broken and some were worn but not bad.

1 Reply

JACOBANDNICKOLAS

MECHANIC
109,755 POSTS

Hi,

First, here are the directions for valve clearance adjustment. The attached pics correlate with these directions.

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1998 Nissan-Datsun Sentra L4-1597cc 1.6L DOHC MFI (GA16DE)
Valve Clearance
Vehicle Powertrain Management Tune-up and Engine Performance Checks Valve Clearance Service and Repair Procedures Valve Clearance
VALVE CLEARANCE
CHECKING
Check valve clearance while engine is warm and not running.

Pic 1

1. Remove rocker cover.
2. Remove all spark plugs.
3. Set No. 1 cylinder at TDC on its compression stroke.
- Align pointer with TDC mark on crankshaft pulley.
- Check that valve lifters on No. 1 cylinder are loose and valve lifters on No. 4 are tight.
- If not, turn crankshaft one revolution (360°) and align as described above.

Pic 2

Pic 3

4. Check only those valves shown in the figure.
- Using a feeler gauge, measure clearance between valve lifter and camshaft.
- Record any valve clearance measurements which are out of specification. They will be used later to determine the required replacement adjusting shim.

Valve clearance for checking (Hot):
Intake: 0.21 - 0.49 mm (0.008 - 0.019 inch)
Exhaust: 0.30 - 0.58 mm (0.012 - 0.023 inch)

pic 4

5. Turn crankshaft one revolution (360°) and align mark on crankshaft pulley with pointer.
6. Check only those valves shown in the figure.
- Use the same procedure as mentioned in step 4.
7. If all valve clearances are within specification, install the following parts:
- Rocker cover
- All spark plugs

ADJUSTING
Adjust valve clearance while engine is cold.

Pic 5

1. Turn crankshaft. Position cam lobe upward on camshaft for valve that must be adjusted.
2. Place Tool (A) around camshaft as shown in figure.
Before placing Tool (A), rotate notch toward center of cylinder head. (See image) This will simplify shim removal later.

CAUTION: Be careful not to damage cam surface with Tool (A).

Pic 6

3. Rotate Tool (A) so that valve lifter is pushed down.

Pic 7

4. Place Tool (B) between camshaft and valve lifter to retain valve lifter.

CAUTION:
- Tool (B) must be placed as close to camshaft bracket as possible.
- Be careful not to damage cam surface with Tool (B).

5. Remove Tool (A).

Pic 8

pic 9

pic 10

6. Remove adjusting shim using a small screwdriver and a magnetic finger.
7. Determine replacement adjusting shim size using the following formula.
- Use a micrometer to determine thickness of removed shim.
- Calculate thickness of new adjusting shim so valve clearance comes within specified values.
R = Thickness of removed shim
N = Thickness of new shim
M = Measured valve clearance
Intake: N = R + [M - 0.37 mm (0.0146 inch)]
Exhaust: N = R + [M - 0.40 mm (0.0157 inch)]

Shims are available in 50 sizes from 2.00 mm (0.0787 inch) to 2.98 mm (0.1173 inch), in steps of 0.02 mm (0.0008 inch).
- Select the closest size shim to the calculated thickness.

Pic 11

8. Install new shim using a suitable tool.
- Install with the surface on which the thickness is stamped facing down.

Pic 12

pic 13

9. Place Tool (A) as explained in steps 2 and 3.
10. Remove Tool (B).
11. Remove Tool (A).
12. Recheck valve clearance.

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Let me know if that helps or if you have other questions.

Take care,
Joe

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