DIY Drive Belt Replacement (Serpentine Belts)
Here's the complete guide to removing/replacing 03-05 G35 Coupe drive belts. Other years may be similar. During this tutorial, you will be shown how to replace both drive belts. The larger (wider) drive belt powers the alternator and power steering pump. The smaller (thinner) belt powers your air conditioner compressor. Inspect belts for cracks, fraying, wear and oil. If necessary, replace.
3/8" drive ratchet
3/8" drive 6" extension
14mm socket (shallow and deep)
Electric Impact Driver (not required, but makes things go much faster. Use 1/4" ratchet as a substitute)
Make sure you get the right belts. Depending on the year of your car, the larger (wider) drive belt that powers the alternator and power steering pump comes in different lengths. From what I've read, some of the earlier G models actually had a mechanical fan, which requires a slightly different length belt. If you have any question about what belt to buy, contact your local dealer and they should be able to confirm the length of the belt for your car's year and model. With that information, you will be able to purchase the correct belt. I ordered a set of pretty blue Gates belts for my 03' Coupe. Why blue Gates High-Performance Belts? Because race car. The Gates part numbers are:
PS/Alternator belt- K060465RB
AC Belt- K040372RB
1.) Remove the lower plastic undershroud. There are a **** ton of 10mm bolts. Use the impact driver to zip them all out until the undershroud is loose. Now would be a good time to scrub it clean before you reinstall it later. Now you should have a clear view of the underside of the engine.
2.) Before taking the old belts loose, go up top and tug on both belts. Get a feel for the tension, so that when you install the new belts, you have an idea how the new belts should feel when installed.
3.) When looking under the car, you can see each of tensioner/idler pullies. The tensioner on the left side of the picture (the 2 red circles) is for the larger drive belt that powers the alternator and power steering pump. The upper bolt (upper red circle) must be loosened first to release the pulley, and then the tension bolt (lower red circle) bolt can then be loosened to release the tension on the belt.
The same applies for the smaller (thinner) belt that powers your air conditioner compressor. The tensioner is located on the right side of the picture (the 2 blue circles). The upper bolt (upper blue circle) must be loosened first to release the pulley, and then the tension bolt (lower blue circle) bolt can then be loosened to release the tension on the belt. These steps are done in reverse order when putting on the new belts.
4.) Use a short 14mm socket to loosen the larger PS/ALT belt's idler pulley.
Then loosen the tensioner bolt using the 12mm socket with extension. Now remove the belt. One way to try and get the belt tension close on the new belt, is to count the number of full turns that you loosen the tensioner bolt when you take the old belt off. When you put the new belt on, tighten it the same number of turns it took you to remove the old belt. That should at least get you close to the proper belt tension.
4.) Use a deep 14mm socket to loosen the smaller A/C belt's idler pulley.
Then loosen the tensioner bolt using the 12mm socket with extension. Now remove the belt.
At this point, all the old belts are removed, and you are ready to install the new belts. This is a good time to check all the pulleys. Rotate each pulley by hand and make sure it spins freely and doesn't squeak. Replace any defective pulleys as needed.
As you can see, I really needed new belts.
5.) route your new belts around the pulleys. Make sure you install the A/C belt first.
6.) Tighten the tensioner bolt on larger PS/ALT belt using the 12mm socket with extension. You can use the feel method coupled with counting turns as I have suggested, or use a tension gauge and the FSM specs. Either way works. The first is easier, the second is more precise, so you can pick.
After you get the belt properly tensioned, tighten the pulley bolt using the short 14mm socket. Double check the torque on the nut with a torque wrench: 30.4 - 39.2 N·m (3.1 - 4.0 kg-m, 23 - 28 ft-lb)
8.) Tighten the tensioner bolt on smaller A/C belt using the 12mm socket with extension. Tension the belt properly using one of the methods described above.
After you get the belt properly tensioned, tighten the pulley bolt using the deep 14mm socket. Double check the torque on the nut with a torque wrench: 30.4 - 39.2 N·m (3.1 - 4.0 kg-m, 23 - 28 ft-lb)
9.) Start the car and make sure everything is operating normally. If you hear squeaking, it's likely you did not tension the belts tight enough. The car should sound smooth with no squeaking or grinding noises. If everything is working as it should, reinstall the undershroud and you should be good to go.