I've got a 99 Montero with about 180,000 on it. I've got what I thought was probably a belt tensioner going bad but the more I read the more I'm confused. On startup it sometimes sounds like it won't make it 500 feet. It quiets down considerably usually within a couple of minutes whether it's idling or being driven. Usually it will go away completely after warming up, but sometimes it takes a minute or two running it up to 4k to completely go away. All things that make it seem like a belt tensioner. The part that confuses me is this. Sometimes it will go all day being started and stopped and run totally quiet. Sometimes the next day or even a few days later it will be totally quiet at startup and usually comes back the first time after being stopped for sometimes as little as a couple of minutes. When that happens it often takes 15 or 20 min at higher RPMs to quiet down even though it is fully warmed up. My guess would be that depending on where in the cycle the engine stops that something is leaking down almost immediately, if it stops in the right place it holds. It's coming up to time to do a belt, it was done at about 120,000 but right now we're down a car and even though it's not driven every day some days it needs to be and can't be down until I'm back to 2 other vehicles. I figure if it's the belt I'll keep my fingers crossed until that time, if it goes then I guess it will get a new engine. But as far as I can tell the belt tensioner should not be effected by where the engine stops. But at times it seems like much more than a valve noise. I'm stumped.

 

Although the Gen II's are not as fussy as the Gen III when it comes to timing belts, I would still tear into the front end as soon as possible to service your belt. Just cross your fingers until you get your second vehicle up and running.
When you do open everything up to replace the belt, I would look around for anything else that needs replacing. At 120k, when I did my t-belt I also replaced the water pump, thermostat, tensioner, pulleys, front cam shaft seals, etc.
It sound like you won't know your problem for certain until you open her up.
Good Luck

 

I'm not a mechanic but I experienced similar noises in my 02 ltd in the past. I thought it might be a timing belt issue but when I took it into the service department it turned out that a pulley needed to be changed. Anyways I hope you find and resolve your issue. Good luck.

 

I checked it out pretty well today with a piece of hose and I'm 99% sure it's coming from the timing belt area. What I don't understand and I hope someone can explain it. If it is the tensioner, why does it stay good for days between being driven at times. But then comes back nearly every time after it is turned off the next time, sometimes for no more than a couple of min. If it's building up enough tension to stay quiet after it has warmed up, why would it lose it after sitting less than 5 min?