| Timing Chain Replacement -- Harmonic Balancer, Timing Chain and Sprockets |
From "Weekend Mechanic"
episode WKM-112 |
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Accessing the Timing Chain and Associated Gears With the fan, water pump, alternator and other parts out of the way, work continues on gaining access to the timing chain. 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. Harmonic Balancer; Camshaft and Crankshaft Sprockets - The next part to be removed is the harmonic balancer that's mounted on the end of the crankshaft. It's designed to absorb engine vibration. Removing this component requires a special "puller" tool that comes as part of a harmonic-balancer set (figure A).
- Assemble the puller by inserting the threaded rod through the puller-boss (figure B) and attaching the protective pilot tot he end. The pilot protects the threads of the crankshaft while the balancer is being removed.
- The puller will be aligned where the bolts attached the pulley the balancer. Be certain to match and select the proper bolts from the set so that the size and threads match up (figure C).
- Line up the puller with the bolt-holes (figure D) and attach it with the bolts.
- Tighten down each of the securing bolts until snug (figure E).
- Now, using the appropriate socket, begin turning the center bolt (figure F ) to "pull" and remove the balancer.
- The final part to remove to access the timing chain is the engine's front cover. Unbolt and carefully remove the cover (figure G). If the cover is bent or damaged, it's best to replace it as part of this project.
- With the cover removed, the timing chain and sprockets are finally revealed. At this point, we were able to visually confirm the excessive play in this worn-out chain (figure H). Under normal conditions, the timing chain should have very little slack in it.
- For this repair to proceed, indicator marks on the crank gear and cam gear need to be brought into alignment by rotating the crankshaft until the marks are aligned.
- On our project car, the harmonic-balancer bolt was missing. This part was replaced, and a spacer installed (figure I) before the gears are aligned.
- With the new bolt installed and tightened, a larger socket is used to turn the bolt and the crankshaft until the marks on the gears are aligned next to each other (figure J).
- When replacing a timing chain, the sprockets should always be replaced as well. These parts typically come as a matched set. The next step, then, is to remove the camshaft sprocket. Remove the three retaining bolts that hold the sprocket in place, carefully pry the sprocket loose (figure K) and remove it.
- Next, remove the crankshaft sprocket. To access it, remove the bolt and spacer installed earlier.
- This sprocket is removed using a three-jaw puller (figure L). Position the pilot into the spacer, and make sure that all three jaws are firmly gripping the sprocket. The sprocket may be on tight, so be patient and careful remove it. You may need to use a pry-bar to hold the puller stationary as you work.
With the crankshaft sprocket removed, we were able to observe the severe wear on the teeth of the sprocket (figure M). This illustrates why it's necessary to replace the gears and chain at the same time. If only the chain were replaced, the worn gears would cause it to still be loose, and damage to the new chain would soon occur. In the segment that follows, the new timing chain and gears are installed.
RESOURCES :
The Complete Idiot's Guide to Trouble-Free Car Care
Author: Dan Ramsey
ISBN: 0028635833
Alpha Books
How Cars Work
Author: Tom Newton
ISBN: 0966862309
Publisher: Black Apple Press
Auto Repair for Dummies
Author: Deanna Sclar
ISBN: 0764550896
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