Daewoo Nubira. Manual - part 98

1A – 8

I

GENERAL ENGINE INFORMATION

DAEWOO V–121 BL4

NOISE DIAGNOSIS

Main Bearing Noise

Step

Action

Value(s)

Yes

No

1

Are dull thuds or knocks heard with every engine
revolution?

Go to Step 2

System OK

2

Check the oil pump pressure.
Is the oil pump pressure low?

Go toOil Pres-

sure Test

Go to Step 3

3

Inspect the crankshaft end play.
Is there excessive crankshaft end play?

0.1 mm

(0.0039 in.)

Go toCrank-

shaft Replace-

ment Proce-

dure

Go to Step 4

4

Inspect the crankshaft journals.
Are the crankshaft journals out–of–round?

0.004 mm

(maximum)
(0.0006 in.)

Go toCrank-

shaft Replace-

ment Proce-

dure

Go to Step 5

5

Inspect the belt tension.
Is there excessive belt tension?

Go toTiming

Belt Replace-

ment Proce-

dure

Go to Step 6

6

Inspect the crankshaft pulley.
Is the crankshaft pulley loose?

Go toCrank-

shaft Replace-

ment Proce-

dure

System OK

Connecting Rod Bearing Noise Symptom

Step

Action

Value(s)

Yes

No

1

Is a knock noise heard under all engine speeds?

Go to Step 2

System OK

2

Inspect the crankshaft connecting rod journal.
Is the crankshaft connecting rod journal worn?

Go toCrank-

shaft Replace-

ment Proce-

dure

Go to Step 3

3

Check the oil pump pressure.
Is the oil pump pressure low?

Go toOil Pres-

sure Test

Go to Step 4

4

Inspect the crankshaft connecting rod journals.
Are the journals out–of–round?

Go toCrank-

shaft Replace-

ment Proce-

dure

Go to Step 5

5

Inspect the connecting rods.
Is there a misaligned connecting rod?

Go toPistons

and Rods Re-

placement Pro-

cedure

Go to Step 6

6

Inspect the connecting rod bolts.
Are the connecting rod bolts torqued properly?

System OK

Go toPistons

and Rods Re-

placement Pro-

cedure

GENERAL ENGINE INFORMATION  1A – 9

DAEWOO V–121 BL4

Piston Noises

Step

Action

Value(s)

Yes

No

1

Are any of the following noises heard: a sharp double
knock when the engine is idling, a light ticking with
no load on the engine, or a ”slapping” noise when the
engine is cold?

Go to Step 2

System OK

2

Inspect the piston pin and the bushing.
Is the piston pin or the bushing worn or loose?

Go toPistons

and Rods Re-

placement Pro-

cedure

Go to Step 3

3

Inspect the piston.
Is the piston broken or cracked?

Go toPistons

and Rods Re-

placement Pro-

cedure

Go to Step 4

4

Inspect the connecting rods.
Is there a misaligned connecting rod?

Go toPistons

and Rods Re-

placement Pro-

cedure

Go to Step 5

5

Inspect the piston position.
Is the piston 180

³

 out of position?

Go toPistons

and Rods Re-

placement Pro-

cedure

System OK

1A – 10

I

GENERAL ENGINE INFORMATION

DAEWOO V–121 BL4

Valve Mechanism or Valve Train Noises

Step

Action

Value(s)

Yes

No

1

Is a light tapping sound heard from the engine?

Go to Step 2

System OK

2

Inspect the valve springs.
Are the springs weak or broken?

Go toCylinder

Head and

Valve Train

Components

Replacement

Procedure

Go to Step 3

3

Inspect the valves.
Are the valves sticking or warped?

Go toCylinder

Head and

Valve Train

Components

Replacement

Procedure

Go to Step 4

4

Inspect the valve lifters.
Are the valve lifters dirty, stuck or worn?

Go toCylinder

Head and

Valve Train

Components

Replacement

Procedure

Go to Step 5

5

Inspect the camshaft lobes.
Are the camshaft lobes damaged or improperly ma-
chined?

Go toCamshaft

Replacement

Procedure

Go to Step 6

6

Check the oil supply to the valve train.
Is the oil supply insufficient or poor?

Go toCylinder

Head and

Valve Train

Components

Replacement

Procedure

Go to Step 7

7

Inspect the valve guides.
Are the valve guides worn?

Go toCylinder

Head and

Valve Train

Components

Replacement

Procedure

Go to Step 8

8

Inspect the valve spring seat.
Is the valve spring seat incorrect?

Go toCylinder

Head and

Valve Train

Components

Replacement

Procedure

System OK

GENERAL ENGINE INFORMATION  1A – 11

DAEWOO V–121 BL4

GENERAL INFORMATION

CLEANLINESS AND CARE

An automobile engine is a combination of many machined,
honed, polished and lapped surfaces with tolerances that
are measured in ten–thousandths of an inch. When any in-
ternal engine parts are serviced, care and cleanliness are
important. A liberal coating of engine oil should be applied
to friction areas during assembly, to protect and lubricate
the surfaces on initial operation. Proper cleaning and
protection of machined surfaces and friction areas is part
of the repair procedure. This is considered standard shop
practice even if not specifically stated.

Whenever valve train components are removed for ser-
vice, they should be kept in order. They should be installed
in the same locations and with the same mating surfaces,
as when they were removed.

Battery cables should be disconnected before any major

work is performed on the engine. Failure to disconnect
cables may result in damage to wire harness or other elec-
trical parts.

ON–ENGINE SERVICE

CAUTION :  Disconnect the negative battery cable be-
fore removing or installing any electrical unit, or
when a tool or equipment could easily come in con-
tact with exposed electrical terminals. Disconnecting
this cable will help prevent personal injury and dam-
age to the vehicle. The ignition must also be in LOCK
unless otherwise noted.

Notice :  Any time the air cleaner is removed, the intake
opening should be covered. This will protect against the
accidental entrance of foreign material, which could follow
the intake passage into the cylinder and cause extensive
damage when the engine is started.