Daewoo Nubira. Manual — part 97

1A – 4

I

GENERAL ENGINE INFORMATION

DAEWOO V–121 BL4

2. Operate the vehicle under normal operating condi-

tions as directed in the kit.

3. Direct the light toward the suspected area. The

dyed fluid will appear as a yellow path leading to
the source.

Repairing the Leak:

Once the origin of the leak has been pinpointed and traced
back to its source, the cause of the leak must be deter-
mined in order for it to be repaired properly. If a gasket is
replaced, but the sealing flange is bent, the new gasket will
not repair the leak. The bent flange must be repaired also.
Before attempting to repair a leak, check for the following
conditions and correct them as they may cause a leak.

Gaskets:

S

The fluid level/pressure is too high.

S

The crankcase ventilation system is malfunctioning.

S

The fasteners are tightened improperly or the
threads are dirty or damaged.

S

The flanges or the sealing surface is warped.

S

There are scratches, burrs or other damage to the
sealing surface.

S

The gasket is damaged or worn.

S

There is cracking or porosity of the component.

S

An improper seal was used, (where applicable).

Seals:

S

The fluid level/pressure is too high.

S

The crankcase ventilation system is malfunctioning.

S

The seal bore is damaged (scratched, burred or
nicked).

S

The seal is damaged or worn.

S

Improper installation is evident.

S

There are cracks in the component.

S

The shaft surface is scratched, nicked or damaged.

S

A loose or worn bearing is causing excess seal
wear.

KNOCK DIAGNOSIS

Definition for Knock

Engine knock refers to the various types of engine noise.
Heavy knock is usually very loud and the result of broken
or excessively worn internal engine components. Light

knock is a noticeable noise, but not as loud. Light knock
can be caused by worn internal engine components.
Loose or broken external engine components can also
cause heavy or light knock.

Engine Knocks Cold and Continues for Two–Three Minutes and/or

Knock Increases with Engine Torque

Step

Action

Value(s)

Yes

No

1

Does the engine knock when it is cold and continue
for two to three minutes or does the knock increase
with torque?

Go to Step 2

System OK

2

Inspect the flywheel.
Is the flywheel contacting the splash shield?

Go to Step 3

Go to Step 4

3

Reposition the splash shield.
Is the repair complete?

Go to Step 1

4

Inspect the balancer and the drive pulleys.
Is either the balancer or the drive pulleys loose or
broken?

Go to Step 5

Go to Step 6

5

Tighten or replace the balancer or the drive pulleys.
Is the repair complete?

Go to Step 1

6

Inspect the piston–to–bore clearance.
Is the clearance more than the value specified?

0.030 mm
(0.001 in.)

Go to Step 7

Go to Step 8

7

1. Rebore the cylinder and hone to size.
2. Replace the piston.

Is the repair complete?*

Go to Step 1

8

Inspect the connecting rod.
Is the connecting rod bent?

Go to Step 9

System OK

9

Replace the connecting rod.
Is the repair complete?

Go to Step 1

* Cold engine piston knock usually disappears when the cylinder is grounded out. Cold engine piston knock, which disap-
pears in about 1.5 minutes, is considered acceptable.

GENERAL ENGINE INFORMATION 1A – 5

DAEWOO V–121 BL4

Heavy Knock Hot with Torque Applied

Step

Action

Value(s)

Yes

No

1

Is there a heavy knock when the engine is hot and
torque is applied?

Go to Step 2

System OK

2

Inspect the balancer and the pulley hub.
Is the balancer or the pulley hub broken?

Go to Step 3

Go to Step 4

3

Replace the broken balancer or the pulley hub.
Is the repair complete?

Go to Step 1

4

Inspect the torque converter bolts.
Are the bolts tightened to specified value?

45N

S

m(33 lb–

ft)

Go to Step 5

Go to Step 6

5

Tighten the torque converter bolts.
Is the repair complete?

Go to Step 1

6

Inspect the accessory belts.
Are the belts too tight or nicked?

Go to Step 7

Step 8

7

Replace and/or tension the belts to specifications as
necessary.
Is the repair complete?

Go to Step 1

8

Inspect the exhaust system.
Is the system grounded?

Go to Step 9

Go to Step 10

9

Reposition the system as necessary.
Is the repair complete?

Go to Step 1

10

Inspect the flywheel.
Is the flywheel cracked?

Go to Step 11

Go to Step 12

11

Replace the flywheel.
Is the repair complete?

Go to Step 1

12

Inspect the main bearing clearance.
Is the clearance more than the specified value?

2.0 DOHC

0.015–0.040

mm

(0.00059–0.001

5 in.)

Go to Step 13

Go to Step 14

13

Replace the main bearings as necessary.
Is the repair complete?

Go to Step 1

14

Inspect the rod bearing clearance.
Is the clearance more than the specified value?

0.019–0.070

mm

(0.0007–0.0027

in.)

Go to Step 15

System OK

15

Replace the rod bearings as necessary.
Is the repair complete?

Go toStep 1

1A – 6

I

GENERAL ENGINE INFORMATION

DAEWOO V–121 BL4

Light Knock Hot

Step

Action

Value(s)

Yes

No

1

Is there a light knock when the engine is hot?

Go to Step 2

System OK

2

Is detonation or spark knock evident?

Go to Step 3

Go to Step 4

3

Check the engine timing and the fuel quality.
Was the problem found?

Go to Step 1

4

Inspect the torque converter bolts.
Are the bolts loose?

45 N

S

m (33 lb–

ft)

Go to Step 5

Go to Step 6

5

Tighten the torque converter bolts.
Is the repair complete?

Go to Step 1

6

Inspect the manifold.
Is there an exhaust leak at the manifold?

Go to Step 7

Go to Step 8

7

Tighten the bolts or replace the gasket.
Is the repair complete?

Go to Step 1

8

Check the rod bearing clearance.
Is the clearance within the specified value?

0.019–0.070

mm

(0.0007–0.0027

in.)

Go to Step 9

System OK

9

Replace the rod bearings as necessary.
Is the repair complete?

Go to Step 1

Knocks During Initial Start–Up But Lasts Only a Few Seconds

Step

Action

Value(s)

Yes

No

1

Does the engine knock during initial start–up but last
only a few seconds?

Go to Step 2

System OK

2

Check the engine oil.
Is the proper viscosity oil used in the crankcase?

Go to Step 4

Go to Step 3

3

Install oil of the proper viscosity for the expected
seasonal temperatures.
Is the repair complete?

Go to Step 1

4

Inspect the hydraulic lifters.
Is there evidence of hydraulic lifter bleed–down?

Go to Step 5

Go to Step 6

5

Clean, test and replace the lifters as necessary.
Is the repair complete?*

Go to Step 1

6

Inspect the crankshaft end clearance.
Is the clearance more than specified value?

0.01 mm

(0.0039 in.)

Go to Step 7

Go to Step 8

7

Replace the crankshaft thrust bearing.
Is the repair complete?

Go to Step 1

8

Inspect the front main bearing clearance.
Is the clearance more than the specified value?

2.0 DOHC

0.015–0.040

mm

(0.00059–0.001

5 in.)

Go to Step 9

System OK

9

Replace the worn parts of the front main bearing.
Is the repair complete?

Go to Step 1

* When the engine is stopped, some valves will be open. Spring pressure against the lifters will tend to bleed the lifter down.
Attempts to repair this should be made only if the problem is consistent.

An engine that is only operated for short periods between start–ups may have lifter noise that lasts for a few minutes. This
is a normal condition.

GENERAL ENGINE INFORMATION 1A – 7

DAEWOO V–121 BL4

Knocks at Idle Hot

Step

Action

Value(s)

Yes

No

1

Does the engine knock at idle when hot?

Go to Step 2

System OK

2

Inspect the drive belts.
Are the belts loose or worn?

Go to Step 3

Go to Step 4

3

Tension or replace the belts as necessary.
Is the repair complete?

Go to Step 1

4

Inspect the A/C compressor and the generator.
Is either the compressor or the generator faulty?

Go to Step 5

Go to Step 6

5

Replace the faulty A/C compressor or the generator.
Is the repair complete?

Go to Step 1

6

Inspect the valve train.
Are valve train components faulty?

Go to Step 7

Go to Step 8

7

Replace the faulty valve train components.
Is the repair complete?

Go to Step 1

8

Check the engine oil.
Is the proper viscosity oil used in the crankcase?

Go to Step 10

Go to Step 9

9

Install oil of the proper viscosity for the expected
seasonal temperatures.
Is the repair complete?

Go to Step 1

10

Inspect the piston pin clearance.
Is the clearance more than the specified value?

2.0L DOHC

0.014 mm

(0.0005 in.)

Go to Step 11

Go to Step 12

11

Replace the piston and the pin.
Is the repair complete?

Go to Step 1

12

Check the connecting rod alignment.
Is the alignment faulty?

Go to Step 13

Go to Step 14

13

Check and replace rods as necessary.
Is the repair complete?

Go to Step 1

14

Inspect the piston–to–bore clearance.
Is the clearance within the specified value?

0.03 mm

(0.0012 in.)

Go to Step 16

Go to Step 15

15

Hone the bore and fit a new piston.
Is the repair complete?

Go to Step 1

16

Inspect the crankshaft balancer.
Is the balancer loose?

Go to Step 17

Go to Step 18

17

Torque or replace worn parts.
Is the repair complete?

Go to Step 1

18

Check the piston pin offset.
Is the offset at the specified value?

0.5–0.7 mm

(0.019–0.027

in.)

Toward Thrust

Side

Go to Step 19

System OK

19

Install the correct piston.
Is the repair complete?

Go to Step 1