Hi there,

I'm fairly new to this forum, even though I have had some Mitsubishi's.
My last one is a Pajero Wagon (Montero)(long version) and I really love it.

However, lately I have gotten a strange sound from the engine/transmission that I just can't figure out. I seems to come from the engine, but it only sounds when I am driving, so I am not 100% sure.
It's a complaining humming sound and I can only hear it with almost no throttle (but not with the throttle released), and especially when the engine is cold. I hear it very well inside the car, but it seems to be loud outside as well because people turn around and look at me when I passes them. I also have a slight vibration in the steering wheel, but the servo seems to work excellent and I am not short of steering servo fluid. The AC works pretty bad right now, but it doesn't seem to have any impact to the sound if I turn it off, so I guess it's not the servo compressor.

Please help me if you recognize this problem. I am starting to lose my mind on it ;-)

Thanks
//Mats

Its pretty hard to diagnois problem sounds over the net but from your description I would say its related to the cam belt and tensioner bearing. Sometimes these will make a noise when starting to go especailly when the belt and bearing is cold at low rpm and under load (driving).

The only way I think you may be able to pinpoint is to have someone sit in drivers seat when cold and put their foot on the brake and rev the motor while you listen for the sound. Make yourself up a crude listening device like a doctors stethesascope using a bit of hose and a funnel pressing the hose at different places on the engine. If you hear it coming from the cam cover you know what you will have to do next.

Jim

Hi Jim,
Thank you very much for your thoughts.

I will take a closer look at the cam belt and the surrounding parts, even though it was changed for only 20'000 km ago, but you'll never know, huh...

The stethoscope idea is good. I have use it many years ago on my old Alfa Romeo's, but never on my Pajero, but it is well worth a try.

Thanks
//Mats

Even though the belt was changed its highly likley that they didn't do the bearings or water pump. It is often a good idea to do all of these as they don't last much past 120ks.

Jim

Hi,
I have the same model as you and had exactly the same noise.
I feared the worst and to me it sounded at first like it was coming from the torque converter and like you the noise was loud enough to turn heads!
I eventually traced it to the power steering pump - try a gentle pressure on the steering wheel with the engine at idle - the whine increases or it did with mine.
Changing the fluid fixed it!
I just sucked out all the accessable fluid from the reservoir - about half a litre and then put in fresh ATF with a tad of fluid conditioner - bingo noise reduced. Took out another half litre and replenished and this time completely quiet and it has remained quiet for 2k miles.
You could fully drain the system by disconnecting a line but my method gets most of the fluid out and is less messy.
I guess the cause is usage related - lots of town driving just breaks down the fluid. :beer:

Hello Wicksy,
Thank you for sharing your experience.

I will definitely try your suggestion and change the servo fluid, and I will do it the way you described it.
And even though it might show that the problem still persists, it can't harm to get some new fluid into the system anyway ;)

But anyhow, I think I found another plausible explanation to the sound.
This morning when I started the car it suddenly got a new characteristic. It started to rev up and down between almost no RPM to 900 RPM together with a painstaking squeaking noise. Then it stopped and the engine started to sound fine again. After some investigation I found out that the AC compressor wasn't moving, and the AC control light on the control panel was also blinking. I restarted the engine without AC, and - no noise. Then, when I engaged the AC, the engine started to rev up and down again and it also started to smell burnt rubber. Conclusion - the compressor is totally and definitely stuck. So the first thing I must do is replacing the compressor, and I can almost guess that they don't give them away for free...Mitsubishi...leeches :gunsmilie:

I'll post an update here when I have more facts.

Cheers
//Mats

Here's some feedback for other with same problem/noise.

My AC compressor is as I wrote in my last post completely dead. The shaft is totally stuck, and I have to disengage it to be able to drive the car.

The humming noise was still loud however, so I figured it had to be something else as well. I changed the steering fluid as Wicksy suggested, but did it twice to be sure that all possible contamination would be removed. And viola, almost all of the noise went away. Beautiful...but, hmm, no, still some intermittent noise. Then I gave the fan belt a quick shower with CRC 5-56 and the remaining noise disappeared immediately.

The conclusion is that I didn't have only one problem but several. Even the AC compressor might have sounded a bit before it got completely stuck.

Changing the steering fluid was the thing that made most effect though. :57:

//Mats