DIY Network

Struts Replacement: Introduction to McPherson Struts Learn the function of struts as part of the vehicle's suspension system. From "Weekend Mechanic" episode WKM-208

There are many things that can cause a vehicle to have a bad ride -- improper alignment, worn out shocks, bad tires, uneven tread-wear, etc. This episode focuses on one specific problem as Weekend Mechanic Bruce Bonebrake replaces a set of worn-out McPherson struts. Included are tips for diagnosing worn struts, instructions for removing worn struts from a vehicle, and steps for transferring parts and installing the new struts.

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Weekend Mechanic Bruce Bonebrake begins work removing worn out struts from the vehicle. The struts on this car were in such bad condition that they needed to be replaced before a wheel alignment could be done.

The problem: On our project car, the vehicle was taken in for a wheel alignment. The alignment, however, could not be performed because the struts were in such poor condition.

DIY Difficulty Rating for Repair: This job is not terribly difficult or mechanically complex. We gave it a difficulty rating of 3 on a 5-point intermediate-level scale. Depending on the nature of the problem, this job might be finished in a single day. Allow yourself an extra half-day, however, to allow for any possible complications or surprises.

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 that are equipped with struts. 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 or replacement parts that 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.

In addition to standard auto-mechanic's tools, the only specialty tools that will be needed for this project should be a torque wrench and spring compressor . An air-ratchet is optional, but will help speed the assembly process.

	Figure A
	Figure B
	Figure C

Introduction to McPherson Struts

• Struts (figure A) are one of the components that help give your vehicle a smooth ride. Not all vehicles have struts. Some have shock absorbers; some have struts; some have a combination, with shocks on the back end and struts on the front. Most front-wheel drive vehicles built after 1975 have struts on the front end. Check your owner's manual if you're uncertain whether your vehicle has struts or not.

• Weekend Mechanic factoid: The familiar "McPherson strut" is named after Earl S. McPherson who invented this suspension system in the 1940s.

• Struts function in a manner similar to shock absorbers to enhance the ride quality of a vehicle. In fact, a strut is technically a specific type of shock absorber. On some vehicles, the strut is also a major component of the front suspension -- so that when it goes bad, both the handling and the ride will be adversely impacted. Condition of struts, therefore, can present a safety issue as well as a ride-quality issue.

• Struts may vary in appearance depending on their application and the vehicle on which they are installed. They typically have a shock-absorber mechanism (figure B) that may fit inside a coil spring.

• Some manufacturers recommend struts replacement at specific mileage intervals. Check your vehicle's owner's manual to see if there is a recommended interval for your struts. Otherwise, indicators that struts are in need of replacement include a marked decrease in ride quality, changes in handling, play in the steering or uneven tire-wear. If any of these symptoms occur on your vehicle, it's a good idea to do a visual inspection of your struts to see if it may be time to replace them.

• Most struts are hydraulic, so check for signs of fluid leakage. Also check for visible damage to the outside of the strut's casing. Check the condition of external support structures or brackets -- such as the coil-spring plate (figure C) -- for signs of damage.

• In our case, the struts on the vehicle were in such bad condition that they needed to be replaced before a wheel alignment could be done.

In the segment that follows, the old struts are removed from the vehicle.

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

Tires, Suspension and Handling
ISBN: 1560918314
Author: John C. Dixon
(Society of Automotive Engineers