DIY Network

Timing Chain Replacement -- Parts Removal From "Weekend Mechanic" episode WKM-112

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Bruce Bonebrake replaces the timing chain on a 1969 Camaro RS. This well-preserved classic has 80,000 actual miles on the odometer. The worn-out timing chain will be replaced with this new, performance chain. Figure A Figure B Figure C Figure D Figure E Figure F Figure G Figure H Figure I

In this episode, Weekend Mechanic Bruce Bonebrake replaces the timing chain on a 1969 Camaro RS. The timing chain is one of the most critical components of your car's engine. It should be checked periodically, and replaced at certain mileage intervals to maintain engine performance. Allowing a timing chain to wear until it breaks can result in serious engine damage.

The timing chain (or in newer vehicles, the timing belt) connects the crankshaft and the camshaft. The crankshaft controls the engine pistons, and the camshaft serves to open and close the valves.

Most cars made after 1980 have a timing belt. A timing belt has specific replacement intervals that should be in your vehicle's service manual. A timing chain may not have specific service intervals, but it should still be checked periodically for wear or play.

The problem: There are several signs that a timing chain may need to be replaced:

• rough idle;
  
• chattering noises from the engine;
  
• or difficulty starting the engine.

DIY Difficulty Rating for Repair: Replacing a timing chain is not terribly difficult, but it does require removing a number of engine components to gain access to the chain and related parts. We gave this repair a difficulty rating of 4 on a 5-point intermediate-level scale. Since the timing chain is such a critical component, and replacing it involves removing and re-installing a number of parts, you should take your time on this project. Allow yourself two full days.

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 harmonic-balancer puller, seal puller, seal installer, three-jaw puller, harmonic-balancer installer and a timing light. An air-ratchet is optional, but will help speed the assembly process.

Diagnosis and Accessing the Timing Chain

• Begin the project by removing the air-filter cover and distributor cap (figure A) to expose the distributor rotor.

  
  

• For a timing belt, typically an access cover can be removed to expose the belt. For the '68 Camaro, which has a chain, accessing the area is more complex. To check for play in the chain, manually rotate the fan (figure B) and watch to see if the distributor rotor (figure C) moves. Since rotating the fan in turn rotates the crankshaft -- and since the distributor rotor is connected to the camshaft -- the fan and rotor should move roughly in unison. If the fan has to be rotated considerably before the rotor responds, this excess play is an indication of severe wear in the timing chain. This was the case in our project car.

  
  

• Drain the radiator by removing the radiator cap and opening the stopcock at the bottom of the radiator. Recover the used coolant in a drain pan, and dispose of it properly.

  Safety Alert: Coolant is highly toxic, and it has a sweet smell. Keep it away from children and pets, and dispose of it responsibly.

  
  

• Unbolt the fan shroud, and disconnect and remove the fan (figure D). With the fan removed, also remove the fan shroud.

  
  

• Remove the fan-belt and pulley (figure E).

  
  

• Disconnect and remove the radiator hose.

  
  

• Unbolt the alternator bracket (figure F) and remove the alternator.

  
  

• Unbolt and remove the power-steering unit (figure G).

  
  

• Remove the water pump (figure H).

  
  

• Disconnect the fuel line (figure I).

In the segment that follows, the harmonic balancer and related parts are removed to gain access to the timing chain. Then, the old chain and cam-sprocket are removed.

Tip: Since timing-chain replacement requires the removal of a number of parts, this is a good time to perform some routine maintenance repairs on your vehicle. Consider replacing belts, hoses, clamps and any worn out parts such as the water pump as part of this overall procedure.

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