Sunday, August 22, 2010

Do It Yourself: Serpentine Belt Tensioner Tool

My daughter's Honda Element needed some routine maintenance; replacement of the serpentine belt that connects the engine's crankshaft to the power steering pump, water pump, alternator and air conditioning compressor. This is a relatively easy job for any shade tree mechanic who prides themselves on completing a Saturday afternoon do-it-yourself project.

If you are about to tackle this task on a Honda Element, you may want to review the great instructions at the Honda Element Owners Club Forum. This site includes the belt routing diagram and handy pointers on how to best get to the belt as there is not much room for you to work around the side of the engine where the serpentine belt is located.

I am a fairly competent DIY mechanic and have a reasonable collection of tools to get the typical maintenance or repair job done. What I don't own is a special tool to loosen the serpentine belt's tensioner pulley. The tensioner automatically applies pressure to the belt to keep it tight while the engine is operating. Some vehicles have a spring-loaded version, while others apply tension with a hydraulic device. All of them require a significant amount of leverage by the mechanic to loosen the tension enough to allow the old belt to be removed and the new belt to be installed.

The tensioner will typically have a standard hex-head fastener for use with the tensioner tool. This is not an actual fastener, so you will not be tightening or loosening a bolt. In the case of my Honda Element, it is a 14 mm, six-point head. There's sufficient room to apply an end-wrench to the fastener head, but the relatively short 14 mm end-wrench does not provide enough length to loosen the tensioner.

Mechanics use a tool made specifically for this purpose. You can find several different styles of tensioner tools available for purchase, like this model from MAC Tools.

Most DIY mechanics do not have a specialty tool like this, often times because they are considered relatively expensive (e.g. $30 - $50) for a job that might only be performed once or twice in a vehicle's lifetime. The cost was high enough to inspire me to seek alternatives and think creatively.

Some vehicles may have enough room so that you may simply use a socket with a short length of pipe slipped over the wrench to extend the lever enough to loosen the tensioner. In my case, the Element had limited space and required a tensioner tool that was off-set to reach around various components in the engine compartment.

It may have been possible to use two wrenches in a cheater configuration like that shown in the photo below.

Although this method may work, I hesitate to treat my tools in such a way. End wrenches are not made to be used in this configuration, and the risk of breaking them or possibly permanently ruining them is just not worth the trouble. The length of the lever is also not that much better than the single end wrench alone, making this ad-hoc tool less than ideal for loosening the tensioner. I knew that there had to be a better option.

Looking at the scrap metal under my workbench, I came upon the following idea. To create a long lever for the 14 mm end wrench that allowed it to be placed in the off-set configuration required by my Honda Element. The metal is nothing special, just some bar stock from an old garage door opener. You may have something similar lying around your shop as well.

This first photo shows the components before assembly. The hardware is standard thread 1/4 inch, by the length required. 

The short strap sandwiches the open-end of the wrench to the longer lever. Once assembled, the bolts should be snug, but there is no reason to over-tighten.

In this photo you can see how the off-set is achieved.

The final photo shows the assembled tool. It worked exactly as needed without risk of damaging the belt tensioner or my tools. The best part is that the total cost for me was $0.00.

The type of serpentine belt tensioner tool that you need for your vehicle may be slightly different, but I hope that these photos help to inspire your own creativity so that you may also avoid the expense of purchasing an expensive specialty tool that you may never need to use again. Good luck with all of your shade tree repairs!