Hi,

My car makes a bit of a rattle sound at exactly 1,100rpm.
It only does when cold (first start of the day, rest of the day it's fine)
It does it for about 1 minute, after that it goes away as it gets some temperature.
It is at exactly 1,100rpm. Any more or any less and there is no noise.
It isn't very loud, it can go unnoticed if you're not listening for it, and sounds somewhat in between a rattle can and a tiny hole in the exhaust.

Any ideas?

Thanks

EDIT:
Searched the forums a bit and another bit of info that might be relevant is that the accessory belts squeak every now and then when cold

Sounds like it could be the cat convertor.. Mine did the same thing at low revs till it warmed up a bit before finally collapsing and blocking my exhaust

I was thinking maybe it was something in the Y pipe as I remember reading it here before but couldn't find it again.

If it is my cat converter what would be the best course of action? Buy a universal cat converter and get an exhaust shop to fit it?

Might be cheaper to get a second hand one and fit it yourself or get an exhaust place to as an aftermarket one may need welding into place.. Another way which is illegal and probably not recommended is removing the cat and smashing the centre out with a rather large pipe

And the way I checked if it was my cat was when I first started the car in the morning and the rattle occurred I reached under the car and slapped/held the cat and listened for the noise to stop

Searched the forums a bit and another bit of info that might be relevant is that the accessory belts squeak every now and then when cold

Could be one of your timing belt tensioners too mate. If it is in engine bay.

Could be a few things but it sounds very much like a rattling baffle in the 'Y' piece. Its a common problem but hard to identify if you are unaware of it. Try and put the car over a pit while its cold. It rattles pretty loudly while its revved cold, then slowly goes away as the exhaust warms up. At cruising speed it kind of gets lost in the background noise or you just get used to it. A tedious but relatively cheap fix is to remove the exhaust pipe, cut it open at the 'Y', remove the baffle, then weld it back up again. The baffle might be doing something useful but I cant say I've noticed any negatives since removing the baffle.

I am starting to think it must be that baffle.
If the rpm are at 1,100 but no throttle is pressed it doesn't make that sound.
Either way it is very slight at this stage and only happens a tiny bit for the first few meters I drive the car (basically 1st gear and 2nd gear, after that it's gone).

Just so long as it's not something that might do harm to the car/engine

The power steering belt can make a grumbling/rattling noise when cold and just above idle with slight load. Tensioning it up correctly fixes the problem.

I've had this a couple of times on two different 3rd Gen Magnas and was the belt tensioner pulley.

The power steering belt can make a grumbling/rattling noise when cold and just above idle with slight load. Tensioning it up correctly fixes the problem.

One of the belts squeaks when cold but goes away after a few minutes. I will look into this as well.


I've had this a couple of times on two different 3rd Gen Magnas and was the belt tensioner pulley.

Do you mean the timing belt tensioner pulley?

I changed the accessory belts over today and the rattle is gone so must have been the bearings?

Thanks to MitsFix for the belts and the over the phone advice and help in changing them.

I've been reading this thread with interest as I have a sound from my TW Magna also at exactly 1100 rpm. It's not there at 1000 rpm or 1200 rpm.
It seems to be some kind of resonance and I would describe it as a vibrating sound.
I have 85,000 km on the clock.

It's very hard to determined which part of the engine it is coming from.

If the car is in park the sound is not produced at any rpm. It does occur in either forward or reverse gears at exactly 1100 rpm.
It tends to be more noticeable when gently accelerating from stop.

Mine doesn't go away when the car warms up, but I think the volume drops a little.

If bearings were the cause you would expect there to be some sound evident at higher rpm rather than it being so specific.
Perhaps it was the belt tension which got sorted when you changed them.

I would be interested if anyone has further suggestions or experience with this kind of problem.

When my Magnas do this I know it is time to tighten the ancillary belts to spec. Never fails to get rid of the 1,100 rpm noise.

Those flat ribbon belts can twang like guitar strings if not tight enough. lol

I had mine just right, then I replaced both idlers, and the noise came back.
Not tight enough, I guess. According to the manual, a pressure of 10 kg should deflect the longest part of the belt by only 1 cm. Bathroom scales tell me 10 kg is as hard as I can push with my thumb. lol

Spokeless that describes the problem I had exactly. I noticed that once warm the noise didn't go away completely, just that it wasn't as loud. Also I noticed that because when cold I was using very little rpm and very little throttle that I was around the 1,100rpm mark much more frequently and for longer periods of time whereas when warm the engine was simply almost never at 1,100rpm and when it was it was for a split moment when taking off at the lights.

Thanks Spetz and MadMax , I'll look at the belt tension and see what happens.

MadMax, do you know if it's just a belt tension problem or whether it means the pulleys/bearings need replacing?

According to the manual, a pressure of 10 kg should deflect the longest part of the belt by only 1 cm. Bathroom scales tell me 10 kg is as hard as I can push with my thumb. lol

You can get one of thoose cheap luggage scales where you hook it to the handle and lift it up to tell you the weight. Just put it on the center of the largest span of the belt, pull till it says 10kg and meassure the deflection with a ruller.

MadMax, do you know if it's just a belt tension problem or whether it means the pulleys/bearings need replacing?

Probably just the belt tension, but while you are under the car you can take the belts off and spin the idlers by hand. One of mine was rough (power steering belt one), so I replaced both, but of course I didn't tension the belts enough so the sound @1,100 rpm is back again. I will fix it one day, at next oil/filter change probably. I need to replace the shredded under bumper splash guard too at the same time. (Got to get one first though. lol)

Will my rattle return once the belts get a bit older and loosen up?
Do you know what it is that rattles?

To be honest I have a slight rattle at idle when hot but not sure if it's lifter noise or something else

I don't think the belts stretch as such, but the ribs do wear and some loss of tension could result. They seem to last well though, I replaced a set at 111,600 km only because there were cracks across the ribs.

The rattle sounds like a heat shield on the exhaust is loose, quite different to lifter noise. I think it is just the belt vibrating and making other bits vibrate as well. If you shine a torch down onto the belts with the cold engine idling, you may see the belts vibrate as you vary the revs by moving the throttle lever on the throttle body slowly.

I've looked at some brand new Lancers, and these flat belts are unbelievably tight straight from the factory, nothing like setting up the correct tension on one of the old "V" shaped belts. (= sloppy, but tight enough not to slip.)

When I tightened my belts I was just using the deflection that the repair manual stated where I could deflect each belt about 7mm give or take.

When my engine is started cold it sounds smooth and no lifter noise. Does this mean that my lifters are ok and that the lifter/rattle noise at idle when hot could be the exhaust heat shield?

Noise I have with my TJ Advance auto sedan might be related to some of the noises mentioned here. I really would like to track it down, but after about of a month of effort have not been successful.

It is there after car has not been used for about 8 hours.

I have eliminated the following:
- Hydraulic lash adjusters (I know what these sound like)
-Power Steering and Alternator belts etc (removed both belts and ran motor - no difference)
-Cam belt and/or hydraulic tensioner (have NTN tensioner fitted 8000km ago and last week checked everything and retensioned)
- Heat shields (checked them all, then ran engine and used stethoscope)

When I start car after about 8 hours standing, there is no noise while in Neutral or Park, even if I rev engine, however as soon as I shift into R or D, there is a grating noise. If I go back into P or N, noise is gone. Going to D or R , the noise returns.

If I let car idle for less than 2 minutes, there is no noise when shifting to D or R. If I do about 4 shifts into D or R, noise goes away. Alternatively if I reverse down my drive, the noise is gone
(about 20 metres).

I think the noise is louder going into R than D.

Left car overnight at local mechanic and next morning I sat in car, ran motor and shifted gear selector, while 2 good mechanics listened under car. The best they could do was say it is transmission end (passenger side) and they thought it sounded like a pump cavitating.

Checked AT fluid again and found level correct, no burnt smell and colour A1. I changed fluid again (even though it was only 8000km old). Found no debris and only small amount of metal sticking to magnet. I fitted transmission cooler at about 100 000km (distance traveled now 228000km), change fluid regularly and use only Mitsubishi fluid. Gearbox performs beautifully. Only thing is sometimes it feels like it is slow to engage and does not seem to hold well on inclines, but maybe this is due to low idling speed (closer to 500 RPM and steady). RPM fell after I installed new oxygen sensor and disconnected battery to reset.

Any ideas?