Replacing the Serpentine Belt on a 2009 Tacoma
The 2009 Tacoma comes with two engines, and the belt routing is completely different depending on which one you have. The 2.7-liter 4-cylinder and the 4.0-liter V6 share a platform but not a belt path. Getting this wrong means you will strip components or end up with a belt that never seats. Below is a breakdown of both routes with practical notes from working on these trucks. If you have the 2.7L 4-cylinder (2TR-FE engine), the belt path runs from the crankshaft pulley upward and clockwise through the following accessories in order: the power steering pump pulley on the driver's side, then to the alternator pulley, down past the A/C compressor, across the idler pulley near the bottom, and finally around the tensioner pulley before returning to the crank. The tensioner is a spring-loaded unit located near the center of the assembly, and it is what you relieve when removing or installing the belt. The factory belt part number for the 2.7L is typically 17720-0D090 or the aftermarket equivalent 6PK1325. That 6PK designation means 6 ribs and approximately 1325 millimeters in overall length. Use that length as a cross-reference. The V6 uses a completely different belt, usually around 6PK2070, so don't assume they interchange.
V6 Belt Routing
The 4.0L V6 (1GR-FE) has a longer belt and a different component layout. The routing goes from the crankshaft pulley around the power steering pump, up to the alternator, then to the A/C compressor, over the idler, and around the tensioner before returning to the crank. The physical positions of the pulleys are more spread out, which is why the belt is longer. If you are trying to force a 4-cylinder belt onto a V6 engine, it will not reach. Period. Here is what actually matters when you are doing this work. You need a 14mm socket on the tensioner bolt, and a breaker bar or a long ratchet handle makes this significantly less frustrating. The tensioner spring is strong, and trying to compress it with just a small ratchet will tire your arm out quickly. I usually use a 3/8-inch drive breaker bar, about 10 inches long, which gives me enough leverage without needing to stretch the tensioner beyond its design limit. One thing that catches people off guard: the alternator pulley is a spline-style pulley, not a keyed one. When you are routing the belt on the 2.7L, the alternator pulley can rotate independently of the alternator body. This means the belt can sit loosely on the alternator pulley while you are trying to guide it into place. Hold the alternator pulley steady with your free hand while threading the belt, or the pulley will spin and the belt will pop off before you get the tensioner compressed. This took me about five minutes to figure out on my first attempt because I was fighting the spinning pulley the whole time.
Another detail people miss: the belt has a specific side that faces outward. The ribs go inward toward the pulleys, and the smooth backing faces out. On the 2.7L, the power steering pump pulley has a ribbed groove that only accepts the ribbed side of the belt. If you try to run the belt backward, it will not seat properly and will likely throw itself off within seconds of starting the engine. I learned this the hard way on a friend's truck. We ran it for maybe ten seconds before it jumped off completely, and by then the belt was already glazed on one side.
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Troubleshooting a Belt That Won't Stay On
If you install the belt and it keeps coming off, the issue is almost always one of three things. First, check that the belt is actually routing correctly around every pulley. Second, inspect the tensioner for free movement. The tensioner pulley should rotate smoothly without any grinding or resistance. If it feels rough or binds, replace it. A binding tensioner will not maintain proper belt tension, and the belt will skip teeth under load. Third, check that the alternator bracket bolts are torqued down. These trucks vibrate enough over time that the alternator mounting hardware can loosen slightly, changing the belt path by a fraction of an inch, which is enough to cause derailment. There is a known issue with the tensioner on some 2009 models where the tensioner arm develops play in the pivot bushing. You can check this by grabbing the tensioner arm and trying to wiggle it side to side with the engine off. Any noticeable play indicates worn bushings, and the tensioner will need replacement rather than just the belt. The tensioner assembly itself is not expensive, but it does require removing the old belt and unbolting the unit, which adds maybe twenty minutes to the job.
Belt Removal Steps
Remove the tensioner cover if your model has one. It is usually a plastic shield held by two or three clips. Place your 14mm socket on the tensioner bolt and rotate the tensioner clockwise to relieve pressure. While holding the tensioner in the released position, slip the belt off the tensioner pulley first, then work it off the remaining pulleys. Note the routing before you remove the old belt, or take a photo with your phone. This sounds obvious but people skip it constantly and then spend an hour trying to remember which groove goes where. Once the belt is installed, start the engine and let it idle for about thirty seconds. Listen for any squealing or chirping noises. A brief squeal on startup is normal if the belt was dry, but constant squealing means the tension is incorrect or the belt is routed wrong. Check the belt tension by pressing down on the longest span between two pulleys with your thumb. It should deflect about a quarter inch, no more. If it deflects more, the tensioner may need replacement. If it does not deflect at all, the tensioner could be failing or the belt may be the wrong length. The serpentine belt on these trucks typically lasts between 60,000 and 100,000 miles, depending on driving conditions and whether the engine has had any coolant leaks that degrade the rubber. Cracking along the rib side is a clear sign it needs replacement, even if the mileage seems fine. A belt that looks fine on the outside but has hardened ribs will slip under load and fail sooner than a visibly worn one that still has some flexibility.
