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

sacrileger

Proven Member
288
40
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:
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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:

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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:

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this is a 1992 6-bolt 4g63 and the cover part number is MD141459 S / MD141461 B:
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Any thoughts as to what could have possibly caused this damage to the timing belt after only 18000 km?
 

waltah

Proven Member
369
154
Mar 2, 2011
fairfield, Virginia
Two things are clear:
1. The belt is (as you say) disintegrating. That is, the rubber is coming apart.
2. Good luck comes to those who do the homework. You don't (as far as you know) have a bunch of bent valves or worse because you went looking for the cause of the 'swooshing' sounds.

The question is, is the disintegrating rubber cause or effect? My GUESS would be 'effect' and I wonder what the various sprockets and pulleys look like.

In particular, I wonder about the oil pump sprocket. A small foreign object -- a washer, perhaps a nut -- jammed in its teeth might do pretty much that kind of damage with the bump in the belt rubbing on the timing cover and pushing it out of shape as a bonus.

You've got to pull the whole works apart anyway. I predict you're going to have some fascinating pictures to show us when you do.
 

sacrileger

Proven Member
288
40
Jun 26, 2016
Orillia, ON_Canada
Show us the tensioners and inspect everything that touches the belt
frankly, i am not seeing anything suspicious... the tensioner looks fine and the only mark on the timing belt cover does not appear to be the same coordinates as the marks on the belt"

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i can attempt to take more pics ... it's very difficult to get in there and focus the camera though
 

pauleyman

DSM Wiseman
8,298
2,843
Nov 19, 2011
oklahoma city, Oklahoma
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.
You shouldn't have any marks on the timing belt cover.
Can you post a few more pics that aren't quite so close up and maybe in focus? I'm all about helping but help us help you please.
 

sacrileger

Proven Member
288
40
Jun 26, 2016
Orillia, ON_Canada
Two things are clear:
1. The belt is (as you say) disintegrating. That is, the rubber is coming apart.
2. Good luck comes to those who do the homework. You don't (as far as you know) have a bunch of bent valves or worse because you went looking for the cause of the 'swooshing' sounds.

The question is, is the disintegrating rubber cause or effect? My GUESS would be 'effect' and I wonder what the various sprockets and pulleys look like.

In particular, I wonder about the oil pump sprocket. A small foreign object -- a washer, perhaps a nut -- jammed in its teeth might do pretty much that kind of damage with the bump in the belt rubbing on the timing cover and pushing it out of shape as a bonus.

You've got to pull the whole works apart anyway. I predict you're going to have some fascinating pictures to show us when you do.

yes.. absolutely! The silver lining is that the belt didn't skip or break otherwise I'd have a serious project on my hands.

Although it's difficult to examine all sprockets and gears in detail, there does not appear to be anything that jumps out. the oil pump sprockets and the belt appears fine too so i am not sure what to think of it... i am not ready to blame faulty belt yet as it was brand new when i put it on. in any case, here's the bottom part where the oil pump sprockets are:

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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.

sorry for not mentioning what car it was when i started the thread. It's a 1990 Plymouth Laser, FWD, non-turbo, no other mods. The car is all stock. i'll add it to my profile. i just posted a few more pics for @waltah .

i was thinking the mark on the belt cover was very likely from the broken off teeth being jammed b/w the belt and cover and then dragged under by the belt.

is there any specific area you would like to see to assess the issue? it's not easy to get in there with a phone; however, i have been looking with a light and mirror and i dont see anything like a loose bolt, washer, etc. and there was not anything other than parts of the belt when i removed the cover
 
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pauleyman

DSM Wiseman
8,298
2,843
Nov 19, 2011
oklahoma city, Oklahoma
I'm more concerned that the entire circumference of the belt looks odd. The only things that touch it are the two pulleys. You're doing a timing belt anyway, get it setup for it and remove that belt. You can then inspect those two pulleys. I wouldn't be surprised if one of them were rough or even completely seized.
 

Dericsh

Supporting Member
1,459
691
Nov 25, 2002
Pearl River, Louisiana
I'm more concerned that the entire circumference of the belt looks odd. The only things that touch it are the two pulleys. You're doing a timing belt anyway, get it setup for it and remove that belt. You can then inspect those two pulleys. I wouldn't be surprised if one of them were rough or even completely seized.
I was about to chime in with this, you’re going to be replacing that belt no matter what so might as well start digging in. You’ll likely find the cause as you go thru it.
 

sacrileger

Proven Member
288
40
Jun 26, 2016
Orillia, ON_Canada
I'm more concerned that the entire circumference of the belt looks odd. The only things that touch it are the two pulleys. You're doing a timing belt anyway, get it setup for it and remove that belt. You can then inspect those two pulleys. I wouldn't be surprised if one of them were rough or even completely seized.
I was about to chime in with this, you’re going to be replacing that belt no matter what so might as well start digging in. You’ll likely find the cause as you go thru it.
well,... if there's a problem, it's not readily manifesting itself; at least not to me. i took the belt off and the only damage is in the area by the exhaust cam and then one small area by the intake cam gear in the pic; otherwise the rest of the belt looks new and healthy. the two pulleys spin freely and happily. they were replaced just recently... the entire timing face is new. the way the belt is damaged does not look like manufacturing flaw. any thoughts....? i am at a loss...

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pauleyman

DSM Wiseman
8,298
2,843
Nov 19, 2011
oklahoma city, Oklahoma
I'm going with foreign object damage for the outside and the most likely foreign objects are the missing teeth. Now for how it's missing teeth, check all possible avenues but I'm going to point at oil pump. crank and cams sort of move or they don't.
 

iugrad92turbo

Supporting Member
12,960
874
May 22, 2007
Kalamazoo, Michigan
Ive lost bolts in that area, and a nut good thing i found them before i fired the car up. Labor on a head job is expensive, plus i got this thing just built up. Did you use oem stuff in the build.or before .
 

DSMPT

DSM Wiseman
2,178
1,761
Jun 12, 2014
Japan / Mexico, Arizona
none of the teeth broke off completely
the entire timing face is new. the way the belt is damaged does not look like manufacturing flaw. any thoughts....? i am at a loss...
To me, it looks like typical damage by too low belt tension. You should also check the hydraulic tensioner itself. Maybe it's already dead or finishing to function.
 

sacrileger

Proven Member
288
40
Jun 26, 2016
Orillia, ON_Canada
I'm going with foreign object damage for the outside and the most likely foreign objects are the missing teeth. Now for how it's missing teeth, check all possible avenues but I'm going to point at oil pump. crank and cams sort of move or they don't.
i have been checking and staring at everything... all the gears move freely w/o a drag. i agree that the damage on the outside of the belt was done by a broken tooth stuck b/w the belt and the cover... four of the six pieces fell out when i removed the cover and that was all... no other foreign objects. there are no other visible areas i can see where the belt could have got caught. i was thinking if perhaps there was not too much pressure on the teeth. i remember putting the belt on and i had to pull the cam gears tiny bit together to put the belt on bc some place on this forum i read i should have 15 teeth between the gears.
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Ive lost bolts in that area, and a nut good thing i found them before i fired the car up. Labor on a head job is expensive, plus i got this thing just built up. Did you use oem stuff in the build.or before .
i was very careful not to drop anything down the timing face... and when i took the cover off, the only thing that fell out were a few of the broken teeth off the belt.

To me, it looks like typical damage by too low belt tension. You should also check the hydraulic tensioner itself. Maybe it's already dead or finishing to function.
i was thinking the belt tension might be the problem too; however, i was speculating it would be too much tension as opposed to not enough bc the belt was pretty tight. when i put timing belts on, i tend to err on the tighter side just to eliminate the possibility of belt jumping a tooth or two on me. moreover, as i mentioned above, i was thinking if perhaps there was not too much pressure on the teeth bc when i put the belt on i had to pull the cam gears tiny bit together to put the belt on to get 15 teeth between the gears... and once the teeth broke off, the tension was relieved and no more damage was done to the belt in any other area. i remember how tight the belt was over the sprocket teeth when i was wrestling with it to put it on.
 

pauleyman

DSM Wiseman
8,298
2,843
Nov 19, 2011
oklahoma city, Oklahoma
i was thinking the belt tension might be the problem too; however, i was speculating it would be too much tension as opposed to not enough bc the belt was pretty tight. when i put timing belts on, i tend to err on the tighter side just to eliminate the possibility of belt jumping a tooth or two on me. moreover, as i mentioned above, i was thinking if perhaps there was not too much pressure on the teeth bc when i put the belt on i had to pull the cam gears tiny bit together to put the belt on to get 15 teeth between the gears... and once the teeth broke off, the tension was relieved and no more damage was done to the belt in any other area. i remember how tight the belt was over the sprocket teeth when i was wrestling with it to put it on.
Explain. You don't tension until after the belt is on and the procedure is very specific. You have no tension at all when you put belt over the gears.
 

sacrileger

Proven Member
288
40
Jun 26, 2016
Orillia, ON_Canada
Explain. You don't tension until after the belt is on and the procedure is very specific. You have no tension at all when you put belt over the gears.
as can be seen from the pics (over-exaggerated for illustration), to get the timing marks aligned and 15 teeth between the cam gears, i would need to pull/rotate the exhaust cam gear clockwise which would increase tension b/w the cam gears. i remember that the cam gears lined up in such a way that i could rotate one cam gear counterclockwise and get 16 teeth which was just too loose or rotate the exhaust cam clockwise and get 15 teeth in between and get nice tension at the top. basically, the cam gears lined up about 15.5 teeth... does that make sense?
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pauleyman

DSM Wiseman
8,298
2,843
Nov 19, 2011
oklahoma city, Oklahoma
as can be seen from the pics (over-exaggerated for illustration), to get the timing marks aligned and 15 teeth between the cam gears, i would need to pull/rotate the exhaust cam gear clockwise which would increase tension b/w the cam gears. i remember that the cam gears lined up in such a way that i could rotate one cam gear counterclockwise and get 16 teeth which was just too loose or rotate the exhaust cam clockwise and get 15 teeth in between and get nice tension at the top. basically, the cam gears lined up about 15.5 teeth... does that make sense?
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No it doesn't. You can put the belt on the gears, line them up and you're done. No slack at all. Zip tie them or better still just out a binder clip on the gear.
 

waltah

Proven Member
369
154
Mar 2, 2011
fairfield, Virginia
The tensioner is not in business when you put the belt on so it goes on slack. You have to position all the sprockets correctly so that when tension is applied there'll be the right number of teeth between the two cam sprockets but this requires no force. When the belt is on and correct positioning of all the sprockets is confirmed -- note the special issue with positioning the oil pump sprocket so the lower balance shaft is in the right place -- then the belt tensioner is adjusted. Then you turn the engine over in the forward direction from the crankshaft and confirm that all the sprockets come back to the right place, i.e., that there wasn't excess slack somewhere.

I'm wondering if the belt wasn't some how put on without slacking the tension and being new it was a bit shorter than the old one and was killed by excessive tension. That would certainly account for all the symptoms/damage.

As Paul said there's a specific procedure in the service manual which is online here. That's how it has to be done.
 

sacrileger

Proven Member
288
40
Jun 26, 2016
Orillia, ON_Canada
No it doesn't. You can put the belt on the gears, line them up and you're done. No slack at all. Zip tie them or better still just out a binder clip on the gear.
i understand... that's the ideal scenario though. i tried it again this aft and when i line up the timing marks on the cam gears and put the belt over it i end up with the 16th tooth on the belt on top of the cam shaft gear tooth so i either have to move one of the cam gears in and then i end up with extra tension on the top part of the belt or i have to move the cam gear slightly out which then gives me tons of play... i am not quite sure how to line the top up in such a way the belt slides in perfectly... i always encounter some tension b/w the gears... for some reason.
p.s. @waltah ^ also suggested the belt was new and perhaps on the short side. how many teeth do guys usually get b/w the cam sprockets?

The tensioner is not in business when you put the belt on so it goes on slack. You have to position all the sprockets correctly so that when tension is applied there'll be the right number of teeth between the two cam sprockets but this requires no force. When the belt is on and correct positioning of all the sprockets is confirmed -- note the special issue with positioning the oil pump sprocket so the lower balance shaft is in the right place -- then the belt tensioner is adjusted. Then you turn the engine over in the forward direction from the crankshaft and confirm that all the sprockets come back to the right place, i.e., that there wasn't excess slack somewhere.

I'm wondering if the belt wasn't some how put on without slacking the tension and being new it was a bit shorter than the old one and was killed by excessive tension. That would certainly account for all the symptoms/damage.

As Paul said there's a specific procedure in the service manual which is online here. That's how it has to be done.
well,... in this case i have no idea what i have been doing wrong as i had encountered excessive tension b/w the cam gears (see my reply to paul above)... but you are thinking along the same lines as i was... the belt was new and likely on the short side of minimum mfg. tolerance bc once about 1/2 dozen teeth were plucked out, the excess tension removed and the rest of the belt was fine. i have another belt with about 30K on it so i will try it on in the morning and see if it works the way paul described above^.
 
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DSMPT

DSM Wiseman
2,178
1,761
Jun 12, 2014
Japan / Mexico, Arizona
as can be seen from the pics (over-exaggerated for illustration), to get the timing marks aligned and 15 teeth between the cam gears, i would need to pull/rotate the exhaust cam gear clockwise which would increase tension b/w the cam gears. i remember that the cam gears lined up in such a way that i could rotate one cam gear counterclockwise and get 16 teeth which was just too loose or rotate the exhaust cam clockwise and get 15 teeth in between and get nice tension at the top. basically, the cam gears lined up about 15.5 teeth... does that make sense?
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I think there is a little confusion. Just to clarify, 15 teeth between "the 12th tooth on both cam gears" has nothing to do with the belt tension. Belt tension is a different thing. You have15 teeth between the both 12th tooth doesn't mean you have the right tension. It means you have the "right valve timing" (Assuming that the piston #1/4 position is properly set at TDC). If you have 16 teeth between the 12th tooth on both cam gears, which doesn't mean the belt tension is loose, you still have the same tension. It means you have a wrong valve timing (either exhaust cam is 1 tooth retarded or intake cam is 1 tooth advanced against TDC. So the timing marks won't line up.)
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pauleyman

DSM Wiseman
8,298
2,843
Nov 19, 2011
oklahoma city, Oklahoma
i understand... that's the ideal scenario though. i tried it again this aft and when i line up the timing marks on the cam gears and put the belt over it i end up with the 16th tooth on the belt on top of the cam shaft gear tooth so i either have to move one of the cam gears in and then i end up with extra tension on the top part of the belt or i have to move the cam gear slightly out which then gives me tons of play... i am not quite sure how to line the top up in such a way the belt slides in perfectly... i always encounter some tension b/w the gears... for some reason.
p.s. @waltah ^ also suggested the belt was new and perhaps on the short side. how many teeth do guys usually get b/w the cam sprockets?
Teeth don't matter. Line up the marks and go. I've done more than 100 and it's the same every time.
 

sacrileger

Proven Member
288
40
Jun 26, 2016
Orillia, ON_Canada
I think there is a little confusion. Just to clarify, 15 teeth between "the 12th tooth on both cam gears" has nothing to do with the belt tension. Belt tension is a different thing. You have15 teeth between the both 12th tooth doesn't mean you have the right tension. It means you have the "right valve timing" (Assuming that the piston #1/4 position is properly set at TDC). If you have 16 teeth between the 12th tooth on both cam gears, which doesn't mean the belt tension is loose, you still have the same tension. It means you have a wrong valve timing (either exhaust cam is 1 tooth retarded or intake cam is 1 tooth advanced against TDC. So the timing marks won't line up.)
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thank you... the pic says all that i was trying to communicate here.
my and @waltah 's theory was that the new belt was slightly under size and to get the belt positioned the way you have it in the pic, i had to rotate the exhaust sprocket clockwise to get the 12th cam sprocket tooth into the correct groove in the belt so i get the correct number of teeth (15) apart... and yes, when i pulled the exhaust sprocket in, the timing mark was slightly off and the tension on the belt excessive, imo, hence the condition of the belt? would that be a possible reason for the damaged belt?
 

DSMPT

DSM Wiseman
2,178
1,761
Jun 12, 2014
Japan / Mexico, Arizona
hence the condition of the belt? would that be a possible reason for the damaged belt?
Could be or could be the belt was stretched and died of old. Anyways like Paul said above that the tooth count doesn't matter for now. If you don't see any more damage/abnormal wear on other parts after inspect all, get a new belt and install it properly. It wouldn't happen again soon if the belt itself was the cause.
 

pauleyman

DSM Wiseman
8,298
2,843
Nov 19, 2011
oklahoma city, Oklahoma
Again there is no tension on the belt. The "tension" between cams is not an issue. If the marks are off with the belt taut between the gears then likely something else is wrong. This is only with the belt on the cam gears and not threaded all the way around yet. The cam sprockets are a fixed distance. If they don't line up check the condition of the sprocket dowels and holes. That is the only variable. Once you get the belt on completely owners sometimes see marks off with the crank on point because the head has been milled too much. Think about it. The belt is supposed to be a fixed distance from the crank counterclockwise to exhaust cam. The only variable distance is between crank and exhaust cam. Which makes sense because that's where the tensioner is. The marks will always line up at the cams if you're starting there. That's how I usually do it. Thread over cams then down to oil pump around crank and then finally over the tensioner pulley. It goes on easily. Then you check marks and finally tension to spec.
 

1990TSIAWDTALON

Moderator
9,693
5,533
Nov 14, 2013
Independence, Kansas
The only thing I see that looks a bit odd is the discoloration of the tensioner pulley on the back edge. I screen shot it and circled the discolored area, not that it has anything to do with it, but mine are usually just silver from the belt going around it. Maybe my old eyes are just "seeing" things too.

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