The Top DSM Community on the Web

For 1990-1999 Mitsubishi Eclipse, Eagle Talon, Plymouth Laser, and Galant VR-4 Owners. Log in to remove most ads.

Please Support STM Tuned
Please Support STM Tuned

1G New timing belt disintegrating after fewer than 18000 km - WHY?

sacrileger

5+ Year Contributor
280
32
Jun 26, 2016
Orillia, ON_Canada
After installing a brand new timing belt and putting on about 18000km, i noticed the timing belt started making rhythmic 'swooshing' sounds as if the belt was flapping and rubbing against 'something' so i took the timing belt cover off to examine the belt and instantly noticed irregular shallow marks on the belt:
You must be logged in to view this image or video.
You must be logged in to view this image or video.
You must be logged in to view this image or video.


the first thing i thought of wearing belt in such a way were bolts on the oil pan flange not being in their proper place, i.e.one or two bolts were too long and making contact with the belt. no such luck. i removed the two bolts right underneath the pulley and nothing changed. the swooshing sound continued.

continuing with my investigation, i noticed that some of the teeth on the timing belt, the opposite side of where the belt made contact with 'something', were partially broken off and some of them were in the process of breaking off; however, none of the teeth broke off completely... and what i meant by 'partially' is that only about 1/2 of the tooth was broken off:

You must be logged in to view this image or video.
You must be logged in to view this image or video.
You must be logged in to view this image or video.
You must be logged in to view this image or video.
You must be logged in to view this image or video.

You must be logged in to view this image or video.


upon further investigation, i wondered if perhaps i put on the wrong timing belt cover as i wondered why is there a gap of about 1/2" between the oil pan flange and the plastic cover itself:

You must be logged in to view this image or video.
You must be logged in to view this image or video.


this is a 1992 6-bolt 4g63 and the cover part number is MD141459 S / MD141461 B:
You must be logged in to view this image or video.


Any thoughts as to what could have possibly caused this damage to the timing belt after only 18000 km?
 

pauleyman

DSM Wiseman
8,171
2,743
Nov 19, 2011
oklahoma city, Oklahoma
the reason why i have been obsessing over the torque b/w the cam sprockets is that i have run out of ideas as to what caused the damage to the belt. i am dealing with some serious drag on the belt and the crankshaft sprocket is pulling really hard on the belt to move all the moving parts above it. while only six belt teeth were ripped out, every tooth on the belt, every.single.tooth, was about to be cut off. using clock analogy, the cuts are on the AM side, it's the side with the most stress on it given the crankshaft rotates in the clockwise direction. the exhaust sprocket puts the pressure also on the AM side of the teeth... see pic below.. every.single.tooth looks that way:

You must be logged in to view this image or video.
At this point you may want to just tear it back down. Remove the spark plugs and pull the cams and inspect. At that point no valves will open and you an spin the crank independently of everything else. The only drag would be the pistons rings. Crank should spin fairly easily. Same for cams. You can inspect all the caps and then bolt a cam down with no rockers and spin it. Make sure both spin freely. Same for oil pump and front balance shaft if you have it. I see no other way to rule out each spinning component except to take the stresses off it so you can feel it spin.
 

1990TSIAWDTALON

Moderator
9,431
5,256
Nov 14, 2013
Independence, Kansas
Is Contitech a name I should be familiar with????
 

DreamChaser7

Supporting VIP
169
109
Jul 18, 2019
Valrico, Florida
So I am by no means qualified to chime in here as I haven't actually built my motor yet, so be nice. But I do recall reading that the exhaust camshaft sprocket will want to rotate one tooth in the counterclockwise direction when released and this shift must be taken into account when installing the timing belt onto the sprockets. Could this be part of the cause and effect here or not relevant and I'm way off?
 

waltah

5+ Year Contributor
369
154
Mar 2, 2011
fairfield, Virginia
the reason why i have been obsessing over the torque b/w the cam sprockets is that i have run out of ideas as to what caused the damage to the belt. i am dealing with some serious drag on the belt and the crankshaft sprocket is pulling really hard on the belt to move all the moving parts above it. while only six belt teeth were ripped out, every tooth on the belt, every.single.tooth, was about to be cut off.

And you're right to be obsessing. Lots of other issues being discussed here but the one that really matters is: What killed that first belt?

I've never been clear on whether you correctly adjusted the tensioner when that first belt was put on. I may be wrong but it seemed possible that you just forced a new belt on without slacking and readjusting the tensioner. In many cases I'd guess that would give exactly the result you got.

Belts vary in size slightly -- the result of manufacturing tolerances. They stretch and wear and the tensioner may be readjusted to compensate after the belt has been in service for a while.
If the tensioner isn't slacked off when a new belt is installed it's likely to be very hard to get it on and if it isn't correctly adjusted at that time then what happened to your belt is a very likely result.
In other words it may not have been the load from some dragging sprocket (that did the damage) but the fact that the belt was too short due to incorrect tensioner adjustment. So (perhaps) 'everything was pulling against everything.'

Edited to change 'path' to 'belt' so that it would, err ... be right rather than ... stupid. Sorry.
 
Last edited:

sacrileger

5+ Year Contributor
280
32
Jun 26, 2016
Orillia, ON_Canada
And you're right to be obsessing. Lots of other issues being discussed here but the one that really matters is: What killed that first belt?

I've never been clear on whether you correctly adjusted the tensioner when that first belt was put on. I may be wrong but it seemed possible that you just forced a new belt on without slacking and readjusting the tensioner. In many cases I'd guess that would give exactly the result you got.

Belts vary in size slightly -- the result of manufacturing tolerances. They stretch and wear and the tensioner may be readjusted to compensate after the belt has been in service for a while.
If the tensioner isn't slacked off when a new belt is installed it's likely to be very hard to get it on and if it isn't correctly adjusted at that time then what happened to your belt is a very likely result.
In other words it may not have been the load from some dragging sprocket (that did the damage) but the fact that the path was too short due to incorrect tensioner adjustment. So (perhaps) 'everything was pulling against everything.'
at this point i cannot be certain of anything hence not correctly installing the t-belt is also on the table. this doubt was also the reason why i invited the discussion posted above re the different techniques of putting tbelts on and whether starting to put the tbelt on from the bottom up brings with it some inherent problem.

i am especially leery of the tiny gap, about 1.5mm, between the top of the oil pan flange and the bottom of oil pump sprocket so i am always making sure there is no slack on the tbelt and i get no more than 9 belt ribs showing (see above).

furthermore, while wrongly tensioning the tbelt was a possibility, the rule of occam's razor tells me that i need to account for all symptoms and the loose/tight tbelt does not account for the gouged tbelt.

i am developing a theory which would account for all symptoms:

1/ some foreign object found it's way into the timing belt area via gap on the bottom b/w tbelt cover and the oil pan flange (see pics in first post).

2/ the foreign object got caught by the crankshaft sprocket and ripped out belt ribs/teeth in two places 13 ribs apart.

3/ judging by the shape, location and depth of the gouges, one of the tbelt pieces got caught and stuck on top of one of the oil pump sprocket ribs; thus, underneath the tbelt, lifted the belt enough to make contact with the oil pan flange and as the bump on the tbelt was being pulled and dragged thru the 1.5mm clearance, the extra stress, load and friction was the reason for the belt ribs being nearly sheared off.

4/ moreover, i see faint skid marks on the edge of the belt (see pics in first post) which would suggest that there was 'something' underneath the tbelt in the place where the gouges are and lifted the belt enough to make additional contact but since there was no object underneath the edge of the tbelt the belt flexed and simply rubbed against the flange but not hard enough to damage it.

in any case, i will count ribs/teeth and examine the sprockets for any marks and telltale signs to confirm/reject my hypothesis today after work...
 

waltah

5+ Year Contributor
369
154
Mar 2, 2011
fairfield, Virginia
I like your theory a lot. Looking at the inside of the belt should let you distinguish between 'primary' damage caused by the foreign object and 'secondary damage' caused by a torn off rib getting stuck on an idler.

Or if the foreign object was flat, you might find no primary mark at all but it might have severely overstessed the belt by keeping it from fitting into the sprocket teeth.

Spacing of the gouges in the belt ought to be related to the circumference of the idler, right? The stuck rib must not have stayed long because the belt is not an integral multiple of the circumference of anything --- it walks around the various rotating parts on subsequent revolutions so wear is distributed evenly.
 

1990TSIAWDTALON

Moderator
9,431
5,256
Nov 14, 2013
Independence, Kansas
Good info!
Thanks Josh!
 

DSSA

Supporting Vendor
636
438
Jul 26, 2002
Hatfield, Pennsylvania
Continental belts have had a bad rap on these cars for decades, but it seems more likely that something else caused the failure this quickly.

I'm not sure I follow/saw how you set tension on the belt upon installation, or I'm just not understanding it.

One very important "Rule of Thumb" when setting tension on the belts...set it *at* or below the tensioner's pressure. The tensioner sets the belt at the "perfect" tension. If you tighten the tensioner pulley to the point where you've further compressed the tensioner rod into the tensioner body, you've now over-tensioned the belt and are asking for possible severe issues.

If you tension the belt with the tensioner pulley *perfectly*, you should be able to turn the engine over several rotations by hand after pulling out the tensioner pin and then be able to easily install the pin back into the tensioner, with no resistance.

Outside of this "perfect tension":

If the pin has to be re-inserted on an upward angle (or the hole in the tensioner rod is *slightly* too high to get the pin back in) you've set the tensioner pulley a little loose---but the tensioner is now pushing on it to take up that slack. This situation uses a tiny bit of the tensioner's potential travel up, but so long as it's only a slight amount, you'll be fine.

If the pin has to be re-inserted on a downward angle (or the hole in the tensioner rod is too *LOW* to get the pin back in) you've set the tensioner pulley too tight, have further compressed the tensioner, and have too much tension on the belt---start over.

The hydraulic tensioner is your "report card" on how well you set the initial tension via the tensioner pulley.
 

1990TSIAWDTALON

Moderator
9,431
5,256
Nov 14, 2013
Independence, Kansas
Nice explanation of the reason we set these motors the way we do. I, myself, have NEVER used the "measured" method, I always use the method @DSSA describes and they always have turned out fine.
Good write up.
 

1990TSIAWDTALON

Moderator
9,431
5,256
Nov 14, 2013
Independence, Kansas
Every PULLEY too. since the back of the belt had damage also.
 

sacrileger

5+ Year Contributor
280
32
Jun 26, 2016
Orillia, ON_Canada
Please fill out a profile. You've been here 6 years and we don't know what car we are looking at let alone mods etc. Difficult to help without some specifics.

Good job finding this before failure!
Maybe I missed it but how old is the tbelt? Not km but age.
i installed the belt as soon as i bought the belt around sept 2019... i have no idea how many months/years it was sitting in the warehouse.

Spacing of the gouges in the belt ought to be related to the circumference of the idler, right? The stuck rib must not have stayed long because the belt is not an integral multiple of the circumference of anything --- it walks around the various rotating parts on subsequent revolutions so wear is distributed evenly.
i theorize that the broken off rib was stuck to the oil pump sprocket which bulged/lifted the belt and scraped it where it made contact with the timing face cover. i looked and there were friction marks on the plastic belt cover and the clearance is no more than 2mm between the plastic belt cover and the outside of the timing belt. also, the belt does not always end up in the same position after each revolution of 360 degrees which would explain the length of the gouges and their spacing, methinks.

Continental's belt line.

Back in the day, they had a worse reputation for failing than Gates did, but I haven't heard of people using them that often on these cars for years.
it sure is a possibility... low quality material and substandard manufacturing

The tensioner sets the belt at the "perfect" tension. If you tighten the tensioner pulley to the point where you've further compressed the tensioner rod into the tensioner body, you've now over-tensioned the belt and are asking for possible severe issues.

i was under the impression that the true role of the hydraulic tensioner is to maintain consistent pressure on the belt as to take out the slack as the belt is ageing and stretching... which happens with new belts over time... hence the tensioner rod will extrude more and more with time while maintaining constant tension on the belt so it's unlikely the pin can be re-inserted perfectly every time.

Every PULLEY too. since the back of the belt had damage also.

besides the abrasion mark on the timing cover and gouged tbelt, there is absolutely no evidence of any problem. since i did not find anything i could fix to prevent the same thing happening again, i defaulted to a hypothesis that a foreign object somehow got inside the timing cover thru the gap between the engine block and the timing cover.

in order to eliminate this possibility happening again in the future, i made my own cover to block the gap... see pic below:

You must be logged in to view this image or video.


i already put on close to 2000 km and so far so good... no visible damage to the belt, no cracks between the ribs so far. let's hope it lasts so i can tag this post as 'resolved'.
 

wparks

Proven Member
63
23
Mar 19, 2012
Fort Collins, Colorado
Make your life a LOT easier and just get a cam gear lock to hold the gears in the perfect position- you can get one on ebay for dirt cheap- just search "4g63 cam gear lock" and get one for $15. I bought the aluminum one, but the plastic one is probably easier to get in there. That way you don't have to hold the gears under tension to align the marks.

Next, double check your tensioner- do the procedure in the factory service manual (if you have one) to bleed the tensioner and make absolutely sure it's not spongy, or replace with a Mitsubishi tensioner (I lost my first belt/valves to a Chinese made tensioner).

Buy a good quality timing belt. Gates is the way to go, black (cheaper) or blue (if you have the bucks. Don't scrimp on brain surgery, parachutes, or timing belts) Make sure when you are done that the gap between the hydraulic tensioner face and the tension lever (tensioner rod extension) is the ~4mm they spec- way to make this measurement easy- measure and mark the thickness of the ramp part of half a clothes pin. (a line for 3mm, 4mm, 5mm, etc) cut off the end skinnier than 3mm and slide the ramp in there until it stops and read the measurement. Makes it very easy.

Lastly, please seal up the big gap at the bottom of the timing cover and the oil pan with some RTV. It is VERY easy for small pebbles to bounce up in there, chew up your belt, then magically disappear. I think that is what happened. Loose rubber teeth would not scallop a belt and gouge a hard plastic cover like that- that was a rock. The timing cover typically warps over the years, and this gap is common. The more rigid grey "high torque" RTV works best, and will be good insurance to keep both rain and dirt out of there.
 

sacrileger

5+ Year Contributor
280
32
Jun 26, 2016
Orillia, ON_Canada
Make your life a LOT easier and just get a cam gear lock to hold the gears in the perfect position- you can get one on ebay for dirt cheap- just search "4g63 cam gear lock" and get one for $15. I bought the aluminum one, but the plastic one is probably easier to get in there. That way you don't have to hold the gears under tension to align the marks.

Next, double check your tensioner- do the procedure in the factory service manual (if you have one) to bleed the tensioner and make absolutely sure it's not spongy, or replace with a Mitsubishi tensioner (I lost my first belt/valves to a Chinese made tensioner).

Buy a good quality timing belt. Gates is the way to go, black (cheaper) or blue (if you have the bucks. Don't scrimp on brain surgery, parachutes, or timing belts) Make sure when you are done that the gap between the hydraulic tensioner face and the tension lever (tensioner rod extension) is the ~4mm they spec- way to make this measurement easy- measure and mark the thickness of the ramp part of half a clothes pin. (a line for 3mm, 4mm, 5mm, etc) cut off the end skinnier than 3mm and slide the ramp in there until it stops and read the measurement. Makes it very easy.

Lastly, please seal up the big gap at the bottom of the timing cover and the oil pan with some RTV. It is VERY easy for small pebbles to bounce up in there, chew up your belt, then magically disappear. I think that is what happened. Loose rubber teeth would not scallop a belt and gouge a hard plastic cover like that- that was a rock. The timing cover typically warps over the years, and this gap is common. The more rigid grey "high torque" RTV works best, and will be good insurance to keep both rain and dirt out of there.
great suggestions... it has not occurred to me to test the tensioner. and you're right,.. i checked the timing cover flatness and it was, indeed, warped... not enough to account for the entire gap but still...

i made my own cover (see pic above) to close the gap as the idea w/ RTV did not come to mind at that time.
 

wparks

Proven Member
63
23
Mar 19, 2012
Fort Collins, Colorado
Sorry, I did not see your fabricated cover before I posted. I just cringe at the idea of driving through a big puddle and muddy water spraying up in there. I also don't really like having to use RTV for this, but it's about the only thing you can do to really seal it unless you can afford a new lower cover. I saw some brand new-old-stock covers on ebay lately in the $200 range and they went like hotcakes. Must be nice.
 

Xarzor

Supporting Member
94
52
Jul 21, 2020
Denver, Colorado
I could be way off base here. I saw the grooves on the back of the belt and remembered Jafromobile talking about the oil pan bolts being different lengths. He said there are a few bolts that are longer then the rest and if not placed correctly they would hit the timing belt. My two cents.
 

sacrileger

5+ Year Contributor
280
32
Jun 26, 2016
Orillia, ON_Canada
I could be way off base here. I saw the grooves on the back of the belt and remembered Jafromobile talking about the oil pan bolts being different lengths. He said there are a few bolts that are longer then the rest and if not placed correctly they would hit the timing belt. My two cents.
i am very anal about having the proper length oil pan bolts in the correct place underneath the tbelt. in fact, that was the first thing i checked thinking i screwed up; however, it was not the bolts.

interestingly enough, i learnt about the pan bolts from jafromobile as well...
 

wparks

Proven Member
63
23
Mar 19, 2012
Fort Collins, Colorado
Sacrileger- you did test the tensioner in a way if you compressed it slowly in a vice to get the pin back in- if it was slow, patient, difficult going to push the shaft back in it should be fine. If it were a new one that spent a lot of time in stock and shipping in odd positions I prefer to cycle the shaft in and out a few times while in the correct orientation just to make sure I work the bubbles out. I think you should be just fine, and you seem to be. When they go spongy you can practically press them in with very little resistance and its obvious. If it were the oil pan bolts causing this I'm pretty sure the problem would have been apparent right off the bat when you rotated the engine manually a few cycles to let the belt tension and make sure the timing marks were still right on.
 

sacrileger

5+ Year Contributor
280
32
Jun 26, 2016
Orillia, ON_Canada
Sacrileger- you did test the tensioner in a way if you compressed it slowly in a vice to get the pin back in- if it was slow, patient, difficult going to push the shaft back in it should be fine. If it were a new one that spent a lot of time in stock and shipping in odd positions I prefer to cycle the shaft in and out a few times while in the correct orientation just to make sure I work the bubbles out. I think you should be just fine, and you seem to be. When they go spongy you can practically press them in with very little resistance and its obvious. If it were the oil pan bolts causing this I'm pretty sure the problem would have been apparent right off the bat when you rotated the engine manually a few cycles to let the belt tension and make sure the timing marks were still right on.
i did not have the tensioner out of the car. i used a compression tool to move the rod into its position by pushing on the arm so i could insert the grenade pin... however, there was tons of shearing pressure when i backed off the compression tool prior to removing the pin. in any case, after this experience, i will be checking the tbelt on regular basis from here on going forward...
 

1990TSIAWDTALON

Moderator
9,431
5,256
Nov 14, 2013
Independence, Kansas
If you can even SLIGHTLY compress any 4g tensioner by hand, it is wore out. Just for reference. I have an old Gates unit (well it looks like their design I'll say) that I keep around because you can press the pin partway in with your fingers. I only keep it around for showing to other people.
 

sacrileger

5+ Year Contributor
280
32
Jun 26, 2016
Orillia, ON_Canada
Am I the only one that thinks the belt was just super old in age (not miles)?
how is one to determine the age of these belts? it's not like they come with a DOT code similar to automotive tires...

Is the new belt setup tracking perfectly straight now?
so far so good... i am checking the condition of the belt every couple weeks or so..
 
Support Vendors who Support the DSM Community
Boosted Fabrication ECM Tuning ExtremePSI Fuel Injector Clinic Jacks Transmissions JNZ Tuning Kiggly Racing Morrison Fabrications MyMitsubishiStore.com RixRacing RockAuto RTM Racing STM Tuned VR Speed Factory

Latest posts

Build Thread Updates

Latest Classifieds

Top