| Timing-Belt Replacement, Pt. 1 -- Accessing the Belt |
From "Weekend Mechanic"
episode WKM-203 |
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In this episode, Weekend Mechanic Bruce Bonebrake replaces one of the most critical of all mechanical elements on a vehicle -- the timing belt. On this work truck, this involves draining the coolant and removing a number of engine parts -- including the fan assembly, crankshaft-pulley assembly, harmonic balancer and timing cover. The water pump and thermostat housing are also removed and the mating surfaces are cleaned. The thermostat and water-pump are both replaced, and related gaskets are replaced. Once the belt is replaced, the process is reversed to reassemble and install all parts. The finishing step is the addition of new coolant. The problem: The engine on our project vehicle (figure A) -- a Chevy work truck -- has a timing belt with more than 70,000 miles on it. Replacing this belt is a regular maintenance job that doesn't need to be done often, but is critical because a failed timing belt can ruin an engine. The belt connects the crankshaft to the camshaft. On many engines, if the belt breaks or fails while the vehicle is operating, the open valves on the engine can come into contact with the pistons, resulting in major engine damage. Check your owner's manual for the recommended replacement period for your vehicle's timing belt. (Typically they need to be replaced at about 60,000-mile intervals.)
DIY Difficulty Rating for Repair: This job is not as difficult or complex as many people might think. We gave it a difficulty rating of 3 on a 5-point intermediate-level scale. Count on it being a day-and-a-half job. It took us 9 hours. Your project time may vary depending on make and model of vehicle.
Important: Included below are the steps in this automotive procedure as shown in the episode. These steps are general guidelines that are applicable to most vehicles. With any particular vehicle, there may be procedures, specifications, settings, tolerances, components, etc. that are specific to that vehicle. There are also variations according to the type and brand of repair-kit you select. Always consult your vehicle's service manual when undertaking significant automotive repairs, and read and follow the manufacturer's directions and precautions that come with your kit or replacement parts. Safety Alert: Always wear eye protection, and follow proper safety precautions, when working with power tools. Safety Alert: As a standard safety precaution, always disconnect the vehicle's negative battery cable before you begin work on any electrical or mechanical components.
In addition to standard auto-mechanic's tools, some of the specialty tools that will be needed for this project include a torque wrench and harmonic-balancer puller. An air-ratchet is optional, but will help speed the assembly process.
Accessing the Belt
- Begin the project by disconnecting the negative battery cable (figure B). This will disable the engine from being able to crank during the repair. (The negative cable is disconnected rather than the positive. If the positive were disconnected, the metal wrench could touch ground during the procedure and cause an arc.)
- To access the timing belt, the first parts that come off are the upper radiator hose and fan shroud. Use a drain pan to drain the coolant from your radiator (figure C) according to your vehicle's owner's manual or service manual.
- Disconnect and remove the overflow hose (figure D). While the hoses are disconnected, it's a good time to go ahead and drain the coolant from the recovery reservoir as well.
Safety Alert: Coolant is toxic, and it's sweet odor may attract pets. Clean up spills immediately, and dispose of old coolant properly. - The fan shroud is held in place by two bolts. Disconnect the bolts (figure E) and carefully lift out the shroud.
Weekend Mechanic Factoid: The fan shroud isn't only there for safety. On a vehicle with air-conditioning, it also helps direct the flow of air. This is an added reason to replace a damaged fan shroud. - Use pliers (or screwdriver, depending on the type clamp) to unclamp the upper radiator hose (figure F).
- With the clamp loosened, carefully remove the radiator hose (figure H).
- Loosen and remove the nuts that hold the fan assembly in place, and carefully lift out the fan assembly (figure H).
- Once it's removed, examine the fan assembly to make sure the fan clutch and other parts are in good shape (figure I).
- With the fan removed, the pulley and drive-belt can easily be removed (figure J).
In the segment that follows, the harmonic balancer and other key components are removed. Once it can be accessed, the timing belt is removed as well.
RESOURCES :
The Complete Idiot's Guide to Trouble-Free Car Care
Author: Dan Ramsey
ISBN: 0028635833
Alpha Books
Auto Repair for Dummies
Author: Deanna Sclar
ISBN: 0764550896
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