Hello guys, yesterday for the first time my 03 Montero Limited(3.8) made a clatter/knock noise from the top end when I first started it and it lasted for like 9-10 secs, almost sounded like there was a lack of oil and it quieted once the oil started circulating. It would make sense as the truck was parked for 5 days straight and it's gotten quite cold here, in the 50s F. Just a little background, the serpentine belt was replaced a month ago, pulleys were inspected by my guy and he noticed that the tensioner pulley was quite new and must have been replaced recently, so ruling that out, Timing belt service was done 20k miles ago according to Carfax and original PO so not worried about that. Again is it normal for engine to knock/clatter for a few short secs until the oil circulated in motor on colder days? I use 10w30 Synthetic oil in it which was changed 500 miles ago, this is the first time it did it, also It was parked for longer that I ever let it and it's been colder here... please advice.

 

Here is a recording of that sound, it did it today as well on a cold start, it certainly sounds like a pulley, it fades within a few secs. Hope it's not in the timing belt as the service was done 20k miles ago, not much... Please take a listen and tell me what you think, we can do better than this guys...reply! lol

 

That sounds like a bad timing belt tensioner. Does the sound go away if you give it a little gas? I would recommend that you address this right away. Do NOT drive vehicle beyond moving it from one spot to another. If you continue driving it, you risk timing belt skipping few teeth and ending up with expensive damage to valves and pistons. Sounds like you've got lied to by PO and Carfax (more like a Carfox...). It's possible that the timing belt was replaced, but they reused old tensioner to save money. Now you got to do it again. Open up reming belt covers. If TB looks good and new, you can just replace the failed tensioner. I believe you don't even need to take off the TB for this. If belt looks old or damaged - replace it. Word of advice - leave the water pump along. There is NO reason to replace it unless it is leaking or failed in some other way. I replaced my OEM Montero water pump at 250k miles (after 3 timing belts) when I did engine rebuild. It looked pristine on the inside.

 

Thanks for the reply Hunter, Yes my old Monteros made this sound too and when we replaced the timing belt and the components, it went away, great that it had to fail on my watch. The sound goes away in like 10 secs after cold start so it's just on it's way out... Is this expensive labor wise? Doesn't look like much needs to come off to get to it...

 

Update, I don't hear that sound today at all, is it possible that it could be the lifters dry of oil from lack of driving? Also I used the old screwdriver and ear trick on the timing cover and I don't hear anything unusual there but there is a slight tick when cold from the grooved top idler pulley area, and I had my new belt squeak recently so might be an aging idler pulley...

 

No, it is not a lifter noise. It is definitely timing belt tensioner. The TB tensioner on these engines is hydraulic type. It is like a miniature strut, using fluid pressure to keep preload on the idler pulley. When it fails, the pressure on the pulley is lower and belt/pulley starts slapping around a little because tensioner rod moves back and forth too much/too easily. It is possible that you are experiencing a tensioner that is just starting to fail vs. completely failed one. This may explain why you don't hear the rattle/slap noise at every startup. Possible reasons for is is tensioner behaving differently at different ambient temperatures, or if the rod in the tensioner rotates just right to re-seal the hydraulic chamber and maintain pressure, etc. The frequency of the noise occurring will increase over time, but there is no way to predict how long it can continue to work. It may go for a month or may fail after a week. You just never know. As far as cost, the part itself is just about $50-80, but you will get charged significantly more if you have to have a mechanic replace it. The procedure to replace it pretty much requires to do a timing belt job (minus replacing the belt). But you got to take off all the accessories, fan, front accessory bracket, timing belt covers (I think all 3 of them), remove old tensioner, install new one, preload tensioner pulley and check to make sure engine timing is correct.