THIS IS HOW I DID MINE IST removed the drive belts I found that they were in bad shape. A lot of cracks on the underside. These are original belts, so it is no surprise that they needed replacement. But it meant a trip to the parts store. I also found a leaking oil pressure sender which I replaced.
The first real trouble I had was removing the bypass hose that goes from the thermostat housing to the intake manifold. It lies in front of the upper timing belt cover on the firewall side, and thus has to come off. Well, it, like a lot of OEM hoses, has those DAMN spring clamps. The ones where you have to get pliers on both ears, squeeze the ears together to increase the diameter of the clamp, and then slide it down. Well in the confined spaces where these hoses are it is nearly impossible to get any type of pliers in there to squeeze the clamp. I really had problems with the lower clamp. I bet it took me 1-1/2 hours to get this hose off. I put it back on with normal worm screw hose clamps, and it was a piece of cake. GGGGRRRRR.
Carl Haines replaced his water pump (and timing belt, etc.) in 2002 and had the following cool idea to help get to these spring clamps:
Coolant hose spring clamps. When working with the coolant hose clamps I recalled what Steve Cutchen wrote on his web page about his trouble and dislike with the spring type hose clamps and replacing it with the worm screw type clamps. This caused the light bulb over my head to light up. Can you see it above my head? The problem is that the position of the spring type clamp does not give adequate access with a set of pliers or channel locks to remove the clamp. My idea was to use a worm screw type clamp to loosen the spring type clamp to release the spring type clamp far enough so that the clamp can be repositioned so that I could gain access with a set of pliers to actually remove the clamp. (The worm screw clamp I used was an old one from a heater hose and could only tighten it far enough to be able to rotate the spring clamp. The clamp did not release far enough for me to clear ridge on the fitting, so I just rotated the clamp so that I could get better access to the ears and then squeeze and remove the clamp with a pair of channel locks.) I actually prefer using the spring type clamps because they provide a constant clamping force and don't tend to leak when the metal fittings contract on cold mornings.
As I understnad this, he's using a small screw clamp on the spring clamp's ears to squeeze them. Then, with the ears squoozen (!) the clamp can be moved off the hose and rotated out of the way. Cool idea!
The A/C drive belt tensioner and the water pump pulley came off next. Then I had access to the upper timing belt cover bolts. Tough to get to, but not too bad. 8mm heads. You'll need a small socket set for this. The difficult part is that the A/C drier and the A/C hoses all run right up against this cover and limit access. I took the speed control actuator loose and then removed the three bolts holding the drier in place, just to give me some push room. It is not easy to get the timing belt cover out from the engine compartment, but it can be done.
On the lower part of the engine, the key was removing the vibration dampner. I have an air wrench, and it had enough power to loosen the big (1-1/16") bolt. Otherwise, I would have had to buy a strap wrench to hold the vibration dampner while removing the bolt. I then used a big wheel puller to remove the dampner from the end of the crankshaft. From this point, removal of the lower timing belt cover was straightforward.
I lined up the timing marks on the cam gears with their marks on the engine and was ready to remove the old belt. (Before loosening the timing belt tensioner, read the section below on Reassembly. Be sure to notice exactly how the 6mm hex hole on the tensioner is clocked. You will want to put it back in the same relative location.) Loosening the timing belt tensioner was easy, and the belt came off no sweat. It looked used, but there were really no bad spots that I could notice visually. I've heard that a visual inspection seldom reveals a timing belt about to fail.
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I was really impressed with Nissan's design of the timing belt. There are three white lines across the belt, each of which correspond to a white mark on either the crankshaft or the two timing gears. Make sure the marks line up with the lines and you are guaranteed to have the right number of cogs between each pulley.
Setting the timing belt tension was odd. In a greatly simplified version, the manual says to set the tensioner 70-80 degrees from its spring loaded position. Then use a 0.35mm feeler gauge between the belt and tensioner to finalize the setting. It's like cut it with an ax and then measure it with a micrometer. I set it to 70-80 degrees and then checked the deflection by the book. I had to go another 10 degrees or so to get a deflection I was satisfied with. I am probably between 75-85 degrees from the spring-rest position.
Since I did my timing belt, I ran across the April 1999 issue of Motor magazine, which had an article on the VG engine. On timing belt tension adjustment, they wrote:
Adjust the VG30 belt tensioner by turning its 6mm hex bolt. Always note the clock position the hex hole is in before loosening the tensioner to remove the original belt. Experienced Nissan specialists report that 99% of the time, the factory's adjustment puts the hex hole exactly in the 5:30 position. For consistent results, they also use a genuine Nissan timing belt and reset the tensioner bolt to its original clock position.
The rest of the car went back together without too much trouble. Getting a few of the timing belt cover bolts to start was a pain, but not too bad.