Timing Belt - Adjustment
88mitsubishi03SUBJECT:
PRECIS TIMING BELT ADJUSTMENT
NO. TSB-88-09-008
DATE July, 1988
MODEL 1988 Precis
PURPOSE
A loose timing belt can cause an engine to be noisy - the most familiar symptom is a "diesel" sound
- and a too-tight belt is subjected to unnecessary stress, which affects not only the belt but also the camshaft bearings. So it is important that the timing belt be adjusted properly. This bulletin contains a detailed procedure for this purpose. Also included is a procedure for measuring timing belt tension when using a tension gauge.
TIMING BELT TENSION ADJUSTMENT
The procedure for adjusting the timing belt and verifying the tension is shown on Pages 2 and 3 of this bulletin.
NOTE: If the belt is being replaced, use the installation and adjusting procedure on Pages 20-30 and 20-31 of the 1988 Precis Service Manual.
TIMING BELT TENSION MEASUREMENT USING A GAUGE
The method of measuring timing belt tension with a belt tension gauge is given on Page 4 of this bulletin.
TIMING BELT TENSION ADJUSTMENT PROCEDURE
If any unusual noise is caused by improperly adjusted timing belt tension, use the following procedure to readjust the tension.
FIGURE 1:
1. Remove timing belt upper cover and water pump pulley.
2. Check the belt for cracking, peeling or other damage. Be sure to carefully check the entire length of the belt.
3. Set the engine so that the No. 1 cylinder is at the compression top dead center. In other words, align the timing mark on the camshaft sprocket with that on the cylinder head. See Figure 1. Note that the crankshaft should be turned clockwise, not in reverse. Turning the crankshaft counterclockwise will cause the tension to become improperly adjusted.
FIGURE 2:
4. Remove the timing belt lower cover.
5. Loosen the tensioner mounting bolts 1 and 2 in that order as shown in Figure 2 to give the timing belt only spring tension.
FIGURE 3:
6. Check the belt to ensure that it is not out of position. Refer to Figure 3.
FIGURE 4:
7. Tighten the tensioner attaching bolts 2 and 1 in that order as shown in Figure 4. If the bolt 1 is tightened first, the tensioner will move with the bolt and cause the belt to become overtightened.
8. Give the crankshaft one turn in operating direction (clockwise) and realign crankshaft sprocket timing mark with the top dead center position.
CAUTION:
Do not turn the crankshaft in a reverse direction. The crankshaft should be turned smoothly clockwise.
9. Loosen the tensioner attaching bolts 1 and 2 in that order as shown.
10. Retighten the tensioner attaching bolts 2 and 1 in that order as shown to the specified torque.
Tightening torque . . . . . . . . . . . . . . . . . . . . . . . 20-26 N-m(200-270 kg-cm, 14-20 lb-ft)
FIGURE 5:
11. Then recheck the belt tension. Verity that when the tensioner and the tension side of the timing belt are pushed in horizontally with a moderate force [approx. 49 N (11 lb)], the timing belt cog end is approx. 1/2 of the tensioner mounting bolt head radius (across flats) away from the bolt head center as shown in Figure 5.
FIGURE 6:
TENSION MEASURING PROCEDURE (when using tension gauge)
1. Rotate crankshaft in direction of irregular rotation (counter clockwise) to position of 90 degrees before top dead center as shown in Figure 6 under condition that adjusting screw, rocker arm is adjusted regularly (where valve clearance is adjusted).
FIGURE 7:
2. Then measure bolt tension in the middle of tension side span.
Torque value of timing belt tension (in cool condition) . . . . . . . . . 9.5-16.5 kg (21-36 ft. lb).
CAUTION
(a) Put arm on bottom of belt teeth. And put spindle on the middle of belt back surface (See Figure 7).
(b) Keep hand off from indicating part.