I have this weird rattle coming from the engine bay. http://www.youtube.com/watch?v=ehC9zaTUwNQ&feature=g-upl&context=G2610b1dAUAAAAAAAAAA It sounds like the source of the noise is behind the crankshaft pulley. I took a stethoscope today and tried to pin it down. However, it virtually resonates all over the engine. Some other symptoms include:
- Appears ONLY when the engine is HOT.
- Recognizable at 800 - 1000 rpm, goes away once rpms are increased.
- If I rev engine to 6000 - 7000 rpm and then back to idle, the noise goes away for 30 seconds, then comes back.
- I drove the car for 10,000 miles already and it hasn't get louder or quieter.
The car has 147,000 miles on it. It's 3.5 V6 2001 Mitsubishi Diamante. The timming belt was replaced, however timming tensioner and pulley weren't. I dropped the alternator and power steering belts and that didn't affect anything.
Could the timming tensioner/pulley sound like this?
What else could produce this rattle?
Any advice is very much appreciated.
Alex

it could be numerous things, may even be internal. but i would check the tensioner pully for the drive belts first. it maybe the alternator bearing. check all that easy stuff first, best way would be to take off the drive belts, and run the car again quickly and see if the noise is still there, then look at the timing belt tensioner

Thanks for your advice. I did take off the drive belts and that didn't affect the noise. I thought about the timming belt tensioner. But it seems that the bad tensioner rattle appears mostly when the engine is cold. (Am I right about this?) However, in my case it's the opposite, rattle appears only when the engine gets hot. I drained and checked the oil couple of times. There are no metal particles or anything else there.
I came across the post about a divider in the exhaust pipe making some noise. Does it sound similar to my problem?

I came across the post about a divider in the exhaust pipe making some noise. Does it sound similar to my problem?

I've never experienced the Y piece rattle but from your description it sounds right....especially as it does it when hot.

I posted a link to show how the engine sounds now. http://www.youtube.com/watch?v=ehC9zaTUwNQ&feature=g-upl&context=G2610b1dAUAAAAAAAAAA
I am hoping, someone who had this Y piece rattle could confirm or eliminate exhaust divider as a source.

I think I've had this sound before... but, nt from around the pulley area and not so loud. It did sound very "mechanical" though. Turned out I hadnt plugged in the breather hose from the rear rocker cover to the inlet. I think it'd be a long shot that it's your problem though.

Once before I put the timing belt covers back on my Exec wrong and it made noises!! :eek2: But more scraping sounds over this rattle.

Checked your oil - dumb question, but I gotta ask. My Exec again is super sensitive to oil levels, even a little low and its tappets start tick lightly. The other thing it'll will to is give a tappet rattle if I've had the front of the car jacked up (at an angle) for long periods of time. It fades once it's bled up.

Tappet rattle sound isn't this sound though. Still, check your oil, look for anything loose or not sitting right.

What work had you done just prior to the rattle appearing? No significant event just prior to the rattle?

I bought the car with this rattle. Not much info about what has been done with it. Aside from being noisy, it runs strong. Oil level is OK as well. I drained the oil couple of times and inspected it for metal particles (along with the filter), but didn't find any. Could the oil pump make this noise?

Could the oil pump make this noise?

Not experienced enough to say sorry.

Sounds like a bearing somewhere. I've heard a similar sound in motorbikes when the camshaft bearings flog out. The fact it doesnt get louder or worse when the engine speed increases, then fades temporarily as the reves fall back to idle says to me to start looking at things bolted to the engine first. I know you've said it doesn't change with the drive belts disconnected, how about the units themselves - air con compressor and P.steering pump? I had a Lantra that snapped two air con compressor bolts and it would rattle at weird revs and under load... related the the harmonics/vibrations of the engine.

It wont be a heat shield ort y-pipe thing, it just doesnt sound that "light". When you had the drive belts off, did you check the idler bearings/pulleys for play?

Yeah, I actually replaced them both today. I ran the car for a while without the alternator & power steering belts. It sounds exactly the same. The last resort is to replace the timming belt components, but what bothers me is that everything is quiet until the engine gets hot. That makes me think that the timming belt tensioner is not the reason. I also suspect the oil pump, since it's mounted on the engine right in this area. I have zero knowledge about how broken oil pump sounds though. Hopefully, someone from the community knows something about it.

Not experienced enough to say sorry.

Sounds like a bearing somewhere. I've heard a similar sound in motorbikes when the camshaft bearings flog out. The fact it doesnt get louder or worse when the engine speed increases, then fades temporarily as the reves fall back to idle says to me to start looking at things bolted to the engine first. I know you've said it doesn't change with the drive belts disconnected, how about the units themselves - air con compressor and P.steering pump? I had a Lantra that snapped two air con compressor bolts and it would rattle at weird revs and under load... related the the harmonics/vibrations of the engine.

It wont be a heat shield ort y-pipe thing, it just doesnt sound that "light". When you had the drive belts off, did you check the idler bearings/pulleys for play?

Anyways, thanks for your input.

Not likely to be the oil pump. (IMHO) They can fail dramatically but then you have no oil pressure. It could be the water pump, idlers or incorrectly set up hydraulic tensioner. Worth a look anyways.

Had another listen. Are you sure that noise isn't coming from the top of the engine?

Agree. I can drop both accessory belts, take off the crankshaft pulley and listen to the tensioner. I am not sure if I can reach the water pump from there though. What would be the best way to check it?

DON"T RUN the engine with the crank pulley off! You will do damage!

Water pump - remove cam belt covers and crank pulley, see if the idlers are on tight, look for play in the water pump and idlers. Check where the hydraulic tensioner is positioned, if it is fully extended it needs setting up from scratch. If the pump or idlers are defective, cam belt needs to come off.

You really need to have a good read of the manual first though.

I did some research online and my problem might be the bad harmonic balancer. Does anyone have any experience with worn balancers? Can they sound like mine http://www.youtube.com/watch?v=ehC9zaTUwNQ&feature=g-upl&context=G2610b1dAUAAAAAAAAAA ?

I have this exact same noise from my 2002 TJ 3.5l V6. I got the car in 2008 at 89,000km and it was doing it then and is still doing it at 165,000km now. The noise hasn't really changed much in that time either so I don't think your car is going to blow up.

I have taken off the drive belts as well and ran it with no change in noise. I went through all my tappets (twice) and its definitely not them. The noise is really hard to pin point. Also it only does it when hot and at idle. I'm thinking that if the harmonic balancer was causing it the noise would have changed significantly when the drive belts were off.

I have this exact same noise from my 2002 TJ 3.5l V6. I got the car in 2008 at 89,000km and it was doing it then and is still doing it at 165,000km now. The noise hasn't really changed much in that time either so I don't think your car is going to blow up.


Was there a cam belt change somewhere in that time period? If not, it is well overdue.
If the belt was changed, did the noise appear then? Possibly the hydraulic tensioner wasn't set up right.

Harmonic balancer isn't likely to be the cause of the noise. I had one fall apart (NOT on a Mitsu product) and there was no noise or any other warning. (Other than a bit of a wobble - and the rubber protruding out the face. lol)

"I don't think your car is going to blow up."

Probably not, but any weird noise means some components are hitting something, or under stress, and likely to wear quicker. If it's in the cam belt area, metal fatigue from the hammering could break something off and cause more damage. Needs looking at.

I bought the car from a Mitsubishi dealer and they done a major service on it a year before I got it, this included the timing belt. I have always suspected the tensioner as all Mitsubishi changes is the belt at the first change. I'm going to do the belt, tensioner and all associated items this year as the belt will be 5 years old now.

To the OP - Does your car have a rough idle, mine did until I ran through some injector cleaner now it is much better.

When you pull it apart, have a look at the hydraulic tensioner. If the rod of the tensioner is fully extended, and the lever that works the idler resting on the end of the rod can move slightly, that's probably the source of the noise. A properly set up hydraulic tensioner should have the holes in the body of the tensioner line up with the hole in the rod, or close to it on a used belt.

If you can't visualise the above, have a look at the manual, or the instructions that come with a new belt kit.

Thanks everyone for your advice. I am going to change all the timming mechanism components soon, as well as the harmonic balancer. There was at least another person who posted the similar issue on the forum a year ago. He couldn't eliminate this rattle after changing or checking virtually everything that's bolted to the engine. Engine swap helped though. I will post some updates as the mystery unfolds.

Any Progress?

i had a TL had i think same noise only when hot sounded little like diesel. Had timing belt changed and tensioners and water pump also plugs and leads. Still made noise changed oil grades several times no different. Exaust y piece was different noise when first excellerated . I removed flap thing inside with piece of wire fixed that rattle or vibration.Never got worse or better till car got written off by P plater running red light didnt have to chase noise no more. Then upgraded to 380 Awesome

Well, I replaced all the timing components and the front pipe. The noise didn't change at all, so timing wasn't the reason. In my case it actually might be the lifters. The noise just resonates all over the engine bay.

Hi Alex -
Well , I have a 96 30m Diamante ( DOHC 24v V6 + 5 speed Tiptronic ) ..225000 km's ,, goes like stink , and has the same noise ! - Its HORRIBLE !
Now , get this , I had learnt to accept this noise over time , alway did it generally when hot , and only at appox 1100 rpm ..esp in Drive or Reverse . Oil change + filters approx 6000kms . I thrash the car , and love its power . Recently i had the experience of loosing Power Steering - thankfully in my back yard just after startup . Traced it to a Crank Pulley , that had come loose , and destroyed the inner boss of the pulley . Basically , some kind of vibration happens at this rpm range , lift it above 1500 and its normal . It sounds like a Bearing Knock in one cylinder nearest the crank pulley . Could be the oil pump ... but one things for sure , it could have rattled my pulley bolt loose .
History ... 123000 garage does Cam Belt . - I buy the car at 125000 ... its always had this peculiar rattle since ive owned it - 10 years ago .
Car starts missing , shuddering at cruise ... then a week later , pulley comes off .
I buy a new Cambelt ( done 100k on it ) ... new cam belt idler , and some auxlillary pulleys also shot - so do them also . another 2nd hand harmonic balancer ( other one was damaged from being loose for some time ) ... then time it up , bolt it back together , all is good ..BUT very soon , its back to the same horrible rattle . I could of sworn for a day or so , the rattle was gone . But , maybe i just concentrate on that , and was looking at other issues like auxillary pulleys etc at the time , as they were hard to find .
Long story short - I have new cambelt in , ( previous tensioner _ - it took 10 minutes to squeeze the tensioner back to the correct place , put grenade pin in ) then tension belt , then work crank back n forwards to get rid of slack , retension cam idler ... when happy , i pull the grenade pin . Check all bolts are tight , throw it back together .
Car runs smooth ...but the rattle is back witha vengance ... and i mean LOUD . I dont have weird miss ..this was because cam sprocket on crank was floating , and it covered the crank sensor with metal . ( cleaned that all up and remounted the sensor ) - all good there .
The noise is shocking when cold , and the loudest when its in drive and or reverse ...like underload ... but is definately not there when you rev it or drive it hard ... well , if it is , its not the same noise . I am expecting either 1 of 2 things :
1 - Bad Tensioner - I know , should of replaced it - I did study its operation prior to placiong covers back on ( yes i bolted up the crank pulley to stop the sprocket + CAS from drifting )
2 - Seriously bad Conrod big end bearing gone .
One things for sure - its getting worse - i have to drive on it sadly for another few weeks before a 500 km trip back home to strip it down again . If i find that its not the tensioner ( some 150$ ) and the hours to pull it down and install it ) i will be upset as hell .
Ive had guys say its Engine Mounts , Powersteering , Alternator ....everything that you can pull off or discount ...even Flexiplate being cracked . Oil Pump or Rod End is about the only thing that i can think of . It makes probably a louder noise than yours in the video . The vibration is felt in the car pedals at 1100 rpm , it also shakes the hell out of the auxillary belts when connected too . Im goimg to pull it down , check the cam belt tensioner , cam sprocket key & crank . BTW - yes , i did use locktight + rattle gun to put the 2nd crankpulley back on . Good luck ... and yes - im gonna need it too .
It seems to be noisier when cold now ...and for one day , its was almost gone . Temp related ? ... surely it would be noisy when hot if oil is thin ... and pump pressure is lower . Maybe its oil pump saying i cant handle cold thick oil ? ... Maybe its cambelt temp length change ...( 1 - 5 degrees at present here in NZ ) .. Has it spun a bearing on the crank ? or rod/s ? . Its always sounded like a mean 6 , after all its got MIVEC . It revs to 7.4 approx when changing if you floor it . Def not lifters ... they make a ticking sound and are spread all over the top section .. its a completely diff sound . This is a growling rumbling rattle , down the bottom , and on the crank pulley end - the other end of the engine is dead quiet . Youd swear the Crank pulley was loose and rattling on the crank , but mine is tight as this time around . ...and is most definately metal to metal ( sadly ! ) . Its a shame , the same car is on Trademe for 2.5k$ for the same kms .. mines in great order with new bushes , new rotors & pads , and internal its mint . 198kW in its day ..and im pretty sure by the pull its still not far off it . BTW - when i found the pulley bolt loose , it destroyed the steel roll pin , ( i had to drill it out and put a new one in ) ... also it had loose cam belt tensioner pivot bolt when inspecting it , also found AC clutch shaft nut loose also !!! All my bearings are new or idlers are new/+ bearings etc . Its internal , you can tell , its got a muffled sound to it . But its not deep inside , because it sounds like its behind the crank pulley , thats why id love to know how does the oil pump get driven .. is it from the crank directly ? - because there is no auxillary timex belt for it like on my 4G63 DOHC Galant .

Hey Satelliteman,
Definitely good luck to you. Hopefully, you'll find the source of this rattle.

As for me, I've driven the car for about 10,000 miles since the time I posted on the forum. No noticeable changes whatsoever. My harmonic balancer as well as crank sproket didn't have any looseness or vibration last time I checked. The only weirdness that I noticed is that the timing belt wobbles a bit on the cam sprockets. The amplitude is probably a few millimeters.

The noise does change with the oil temperature. It's louder and just different when the car is cold. At some point engine begins to sound normal. And when the engine gets hot, this weird rattle appears. The noise also depends on oil viscosity. The higher the viscosity the louder. I used to put 5W20in the engine and it gets much quieter.

Bottom line, I gave up on this. I already invested more than this car is worth, so I plan to drive until it dies.

I did order a set of new lifters though. I plan to install them in a month or so, when the weather get cooler. I will post another update then.

I have this same noise. It only happens when hot and at idle. I have tracked it down to cylinder No 2 using evoscan to shut down the injectors one at a time (can also pull the plug off the injector while its running). It's not the injector since I swapped them around and the problem does not move cylinders. I'm thinking it may be the exhaust gasket. I've been through the tappets as well so its not them. Anything else I can think of would require getting deep inside the engine.

Satelliteman and AlexLbn can you try pulling the injector plugs on the front bank one by one to see if the noise stops. Pulling the one on the pulley side stops the noise on my engine.
Cheers

Disabling an injector simply makes that cylinder not work. (obviously)

If it eliminates the noise, it could be:
Piston slap (worst when cold)
Big end bearing excessive clearance (worst when hot and under load at low rpm)
Small end bearing excessive clearance ( worst when hot and under load, but a much more high pitched rattle)

Well , I have had the car up on a hoist after talking to a mechanic . Luckily he is a mate , so no charge .
Inetersting ,. as soon as heard it , he reckoned it was cam belt flap .
So , this was good news , since i had done the belt myself , and thought , well perhaps i had done it wrong , and didnt tension it correctly .
We dismantle it all , retension the belt , and then bolt the hold the crank timing pulley on with bolt & large washer . Start it , and no rattle at 1100 rpm where it usually is .
So we think its fixed .. try it under load , and it seems to be gone .
reinstall the cam covers , crank pulley ( do that up by locking the flexiplate bolts against the bellhousing . ( small access cover allows you to put right angl;e bar in while you swing with massive bar on crank bolt when using a hoist )
We put all the belts back on , and run it .
SADLY - its back to the same noise - The crank pulley seems to amplify the sound , and causes the belt driving the alternator etc to flap / resonate .
I too have concluded that I can buy another car just the same for 2500 $NZ in great order . So im gonna drive it till it blows too ( Seems horrible to say that , as i always like to fix problems before the get worse . But real engine out repairs are just too expensive for this car unless you have the hoist in your own home .
Mine is actually the worst when COLD , it seems to be related to load , ie , when you place the gearbox in drive / reverse ...its then that it pulls around 1000 ish rpm ..you can get it to be worst by lifting the rpm to the most reasonant spot ...ie 1000 - 1100 rpm . You would swear metal to metal is wanting out of there .
I do find that when the engine / trans is hottest it is the quitest , but still there .
I will try the disable solenoid idea and report back . I have been tempted to pull the bottom sump off to inspect . Ideally , I should of done this when I had the cam belt covers off , as you can then pull the skirt off aswell as the oill pump body by the looks . I could of checked big ends then i imagine ...concentrating on pistons nearest the crank pulley . I found so many shot bearings when i did the cam belt that i was sure that i had a sweet sounding machine to be presented with when i was done . But sadly , just hundeds of $$ down the drain as far as the noise goes . Sure , ive protected having the engine damaged should a belt break ..but other than that , no luck .

Well I tried number 2 ( im picking its 2 ..most left hand front bank ) ... The rear bank appears to be offset to the left , so i gather that is No 1 .
Well , if you pull number 2 ..it naturally runs badly 5 / 6 ..but i would say that the noise is even worse . I cant get to No 1 its under the intake manifold ..( do i have this right ? )
I am pretty sure its a harmonic of some type , as the engine feels like it has vibration at 2100 approx rpm aswell ... could be double the 1050 approx rpm ..where its the worst .
I dont have a good breakdown of the parts used on the crank ... What exactly makes up the oil pump , pressure relief etc .. Im trying to imagine what happens if the oil pump itself is failing ?
What could create an out of balance engine to make it vibrate so bad at these low rpm , but yet i can make it swing to 7200 at a glance ?

Well , I just read a Youtube reply ...
Someone posted a video on engine noise in 6G72 that was cause by a bad balancer ... which in turn damaged the No 1 cyclinder bearings .. whether it was big end or not they didnt say .
But , it has to be said , my pulley did eventually come loose & fall off . I residing to the fact untill I get enough time to pull the bottom off the engine ,and have parts on hand , it will have to stay like it .

You are correct about which one is number 2. I think we have different problems because mine only does it when fully warmed up and yours mostly when cold.

My TL had a noise like this. I had a theory it was the starter motor. Sounds wily at first, and I never tested it but I always considered that the drive dear on the starter motor was somehow loose. Giving it this intermittent tappet sounding rattle.

Just a theory.

Thanks Jimbo -
You are prob correct . I drove it today about 22kms .. straight out of the garage , you wanna get the rpm up straight away above 1200 or so so it dissapears / masks it !
Cold mine sounds quite / almost too V6 ish ... what sounds like a engine knock alomost when you pull through 2 - 4/ 5ish grand ..( but this is cold ) .. at 1000 - 1100 its a shocker with real vibration / out of balance issues ., and a noise if your under it is def at the crank pulley end . When hot - Well I drove 22kms , did a job for 1/2 hour , restarted the car , pulled away and gave it some stick .. usual ( but quieter rattle at idle ) ... whipped it up to 3 - 5 k and its was awesome .... and didnt sound knocky . Im bugged if i know . Without stripping the beast , doubt we will find out the real story unless something finally lets go. What I would like to know is what is usual oil pressure cold / hot ... and what happens if the relief valve is broken .. can it bounce around ? a Oil pressure guage is something i reckon they should ALLWAYS install in cars ... a liquid filled / damped gauge .. proper industrial version so that you really can see whats going on in that dept . ( tapped in AFTER the Oil filter )

I must look into fitting a gauge just to see what is going on with the oil pressure