Hi everyone,

I did a search for my problem and read previous posts, but I did not find anything that fit completely with what I am experiencing.

I have a 02 Montero Limited with 55K miles on it. A few months back it started to make a Loud Knocking noise on cold starts that would go away within 5 minutes of driving or so. It was not there all the time either, it would be there for a few days in a row, and then go sometimes up to 3 weeks without a sound. It seemed the warmer it was outside, the less it did it. I tried taking it to the dealer a couple of times, but they always said they could not replicate the noise. Which is believeable since it was not always there.

Here is where the story turns, I just got the fluids changed in the car at a reputable place in my area. Oil, Transmission Fluid, Radiator Fluid were all changed, ever since then the noise has been much louder. The noise will go away, but it seems to take longer, around 10-15 minutes of driving. The noise also goes away is when I am accelerating and the engine is at higher RPM's of about 2500+, but when the engine shifts into a higher gear and the RPM's drop again, the noise comes back.

Here is a video link, this is pretty close to what my engine sounds like now:

http://www.youtube.com/watch?v=_0CBQcccLDM

I know it can be a bearing, but with a bearing would the noise go away at higher RPM's? And why since the fluids were changed did the noise get worse?

A little background, I bougt the vehicle with 35K miles on it, I have given regular oil changes with synthetic oil since I got it. I can't say how well the car was maintained before I purchased it, but physically the car was in great condition, so if that speaks to how they may have maintained the engine, then they may have done their part. But maybe they didn't.

Any opinions would be great.

It is going back to the dealer tomorrow morning, I am just looking for some opinions on what I may be getting into.

Another note, I bought the car as a Certified Used Mitsubishi with the 10 year / 100K mile drivetrain warranty from the original in service date, so it is still under warranty. Has anyone ever had any work done under a Certified Used Car warranty? Is Mitsubishi pretty easy when it comes to their warranty's? Or am I going to be in for a long road to get them to cover something?

Thanks in advance for any opinions.

Did some digging around with google, I think my car has Piston Slap. It looks like it meets all the symptoms, loud knocking when cold, goes away as the engine warms up.

Does this sound right? Has anyone else had this problem with their Montero?

It's not just a Mitsu thing. Piston slap happens to most car manufacturers. Since your symptons came about after the fluids were changed, have you checked the oil level? You also may want to ensure that the correct viscosity of engine oil was used. A few years ago, I had a Montero Sport with a 3.0L and it had the same symptons. I’m not recommending the following; I’m just letting you know what worked for me. I dumped an oil additive (STP, I think) in the crankcase at one oil change and there was a slight improvement. At the next oil change, I used Marvel Mystery Oil and the noise decreased even more. The noise was not fully eliminated, but was reduced considerably. I put another 70k on that SUV before trading it in. Good luck.

its a failing timing belt tensioner.

get it fixed immediately.

Are you saying that the timing belt tension is out so it slipped a few teeth or loose so its slightly out of tension? The knock is actually valves hitting the pistons? Ouch!

no, its the failed tensioner making the noise.
keep driving though, and it WILL get worse, and the timing COULD jump.