1. CHAPTER 8.1
Underhood Inspection

2. Introduction
Regular inspection of a vehicle helps ensure the safe and reliable operation of a vehicle.
Types of inspections
Underhood inspection
Exterior inspection
Certain in-vehicle inspections
Under-vehicle inspection
Check fluid levels, lighting systems, etc.
Faults or concerns should be noted for service or repair.

3. Underhood Inspection
Performed at manufacturer’s recommended intervals and prior to long driving trips
Component damage or failure is often caused by a lack of service or low fluid level.

4. Fluids Always use the recommended type and amount of fluid.
The quality of fluid is important.
Nearly all fluids get old, wear out, and require replacement.
There may be a change in color or consistency, a mix of fluids, or change in smell.

5. Engine Oil (1 of 2)
Level of oil in engine lubrication system is critical to its operation.
If too low, oil pump will starve for oil.
If too high, oil will be struck by the crankshaft, churning it into foam.

6. Engine Oil (2 of 2)
Oil level should be checked periodically, usually at every fuel stop or two.
When checking oil level, consider checking if it is time for an oil change.
The manufacturer will specify the vehicle’s oil-life monitoring (OLM) system.
Levels should be checked first.
A low reading could indicate a seal or gasket is leaking or engine is burning oil.

7. Engine Coolant (1 of 3) Checked whenever the oil level is checked
Engine cooling system depends on coolant to transfer excessive heat from engine to the radiator.

8. Engine Coolant (2 of 3)
Some have a transparent reservoir marked with “hot” and “cold.”
Some may have an overflow tank.

9. Engine Coolant (3 of 3)
Low coolant levels can cause engine overheating.
Coolant freezing point is also checked.
Anti-freeze protection level is checked with an anti-freeze hydrometer.
A refractometer can also be used.

10. Brake and Clutch Fluid (1 of 3)
A hydraulic braking system depends on brake fluid.
Brake fluid should be checked whenever the oil level is checked, or monthly.
Check the color of the brake fluid.

11. Brake and Clutch Fluid (2 of 3)
Most brake fluids are hygroscopic.
Check the fluid with either a brake fluid tester or brake fluid test strips.

12. Brake and Clutch Fluid (3 of 3)
Manual transmissions have hydraulic clutch system.
Uses both master cylinder and brake fluid
The brake fluid reservoir also may supply the clutch master cylinder.
The clutch may have a separate fluid reservoir.

13. Power Steering Fluid (1 of 2)
Power for the power-assisted steering systems usually comes from an engine-driven hydraulic pump.
Some use an electrically driven pump.

14. Power Steering Fluid (2 of 2)
The fluid level must be at proper level to avoid drawing air into hydraulic system and to prevent fluid overflow when engine is hot.
The fluid can be checked with a dipstick connected to the filler cap.
Also check the appearance of the fluid.
Dark or black fluid usually means fluid is old and needs to be changed.

15. Automatic Transmission/ Transaxle Fluid (1 of 3)
Correct fluid level is critical to the effective and efficient operation of the transmission.
If level is too low, slipping and shift timing faults can result.
If level is too high, transmission will churn and aerate.
Fluid level is usually checked with a dipstick located under the hood.

16. Automatic Transmission/ Transaxle Fluid (2 of 3)
If adding transmission fluid, make sure to select the correct fluid.
In a manual transmission/transaxle, low fluid levels result in early bearing failure.

17. Automatic Transmission/ Transaxle Fluid (3 of 3)
Vehicle must be level.
Usually accessed through a fill plug on side of transmission/transaxle
Carefully stick a finger in hole and bend finger down to feel level of fluid.

18. Diesel Exhaust Fluid
Some late-model diesel-powered vehicles use diesel exhaust fluid (DEF), or AdBlue™.
DEF is injected into exhaust stream to reduce oxides of nitrogen.
DEF needs to be replenished periodically.
Filler cap is often located under hood and may be colored blue.
Do not put washer fluid in the DEF tank.

19. Windshield Washer Fluid (1 of 2)
The washer system must be ready to work when the windshield is obstructed.
The washer fluid reservoir is normally located under the hood of the vehicle.

20. Windshield Washer Fluid (2 of 2)
Fluid should be checked when oil is changed.
Use properly formulated and mixed washer fluid.

21. Engine Drive Belts (1 of 4)
Operate various accessories on the engine
These belts will wear along with associated idler and tensioner pulleys.

22. Engine Drive Belts (2 of 4)
V-type belt
Sits inside a deep V-shaped groove in the pulley
The sides of the V-belt contact and wedge in the sides of the V in the pulley.

23. Engine Drive Belts (3 of 4)
Serpentine-type belts
Have a flat profile with a number of grooves running lengthwise along the belt
Grooves are exact reverse of grooves in outer diameter of the pulleys.
Check the drive belts whenever the hood is opened for service.
Water pump is most important component driven by the belt.

24. Engine Drive Belts (4 of 4)
The engine will quickly overheat if belt breaks or comes off.
Vehicles using a serpentine belt also have a spring-operated tensioner and pulley.
Stretchy belts or StretchFit™ belts
Don’t use a method for tensioning the belt
Stretchiness applies appropriate amount of tension to the belt over its useful live.

25. Belts Belts should be checked for: Cracks Oil soaking Glazing Tears
Bottoming out

26. Hoses (1 of 2)
At the radiator, there will be a large upper radiator hose and a large lower radiator hose.
Smaller heater hoses run from engine block, manifold, or water pump to connections at heater assembly.

27. Hoses (2 of 2) Engine should be cool when inspecting hoses.
If hot, look for bulging in the hoses.
One defective hose usually means other hose(s) may be deteriorating.
Check for any small hoses that may connect components.

28. Changing the Air Filter
Engine needs a free flow of clean air to operate correctly and with low emissions.
If the filter is not fitted correctly or sealed properly, air can bypass the filter.
The location of the filter will vary.
While inspecting the air filter, check the air cleaner housing and duct work for cracks or holes.

29. Summary (1 of 5)
A check under the hood is important to the life and operation of the vehicle.
Correct type and amount of fluid is important for reliable and safe operation of the vehicle
Engine drive belts and coolant hoses should be inspected and replaced according to manufacturer’s service schedule.

30. Summary (2 of 5)
The engine needs a free flow of clean air from the air filter in order to operate correctly.
A periodic inspection of the vehicle’s exterior can prevent troubles that may cause safety or operational concerns.
Once a month or prior to any long trip, a vehicle should be visually checked for overall roadworthiness.

31. Credits
Unless otherwise indicated, all photographs and illustrations are under copyright of Jones & Bartlett Learning.