Timing Belt Broke While Driving

[threecaster]

MKII Jetta Carat, 1.8L

Just changed the head gasket, and was taking it for a test drive. Ran Great! Must have overtightened the timing belt, cause it broke like 30 minutes after first start.

But it broke going up the road. Heard it go WZZZZZZ...

Did not try and start it or anything tho....had a feeling what it was when it happened (it was making a whining sound, thought either the belt was rubbing the shroud, or the tensioner needs changing...)

Is there the slightest chance I can get lucky at all with this, or can I go ahead and assume bent valves?

What would happen if I reset the cogs, install new belt and fire it up?

[WaterWheels]

What would happen if I reset the cogs, install new belt and fire it up?

That would be my plan of action if it were my car. First inspect the belt and the engine for any signs of a problem other than just having it installed too tight or old age. Rub marks on the belt ot engine, spin the tensioner to see if it rotates quiet and smooth, those kind of inspection things. You don't want to install another belt just to have it snap due to there being a problem. If all looks fine, install the new belt and strat up the engine. You are going to need a new belt anyway and if there is damage (doubt there is) it will not get damaged any more than it already is. If it runs fine then just forget what happend and drive on.

[threecaster]

Splendid!

I was feeling sort of bummed out, having her run so good, then Blomp!


Your comments improve my optimism, as no really nasty noises, just one cog spinning onthe broke belt...


I shall proceed, and shall post my findings...

[threecaster]

Well, new belt on, fired up on the first lick! Rev'd slightly and went to idle.

I'm running it (temporarily) with only the main pulley on...no pumps or alternator.

There is still that whining sound from down around the bottom pulley, sounds almost exactly like an old power steering pump. (maybe my oil pump?, tested 88psi about 3 yrs ago...)

Though I am running with a quart of Marvel Mystery Oil to help rid the water that polluted from the old head gasket....

There does seem to be a new "chuttery" sound from the #1 area of the head. I'm thinking this is the sound of a bent valve.

The car is out on the street, as soon as it stops raining, I'll put the wheel on and garage her. Then I'll see about a compression test, and maybe peek into the cylinders...

Bout makes me want to cry tho....

Any thoughts?

[WaterWheels]

. . . fired up on the first lick! Rev'd slightly and went to idle.

There is still that whining sound from down around the bottom pulley, sounds almost exactly like an old power steering pump.

There does seem to be a new "chuttery" sound from the #1 area of the head. I'm thinking this is the sound of a bent valve.

Normally an engine with a bent valve will not fire up like you seem to indicate. With that engine you really should not have any piston to valve contact. But doing a compression check would be a wise thing to do just to see.

Whining sound could be the belt being adjusted too tight. People often set the tension too tight and the manuals are not real great with stating how tight it should be. Try backing the tension off a touch and see if the sound goes away or changes. If it does then that is the whine problem unless the tensioner itself is bad. Check the plastic belt covers also for correct fitment. Sometimes you can mount them where they seem to be on right but they are just a little off and it rubs on the belt or vibrates. I had a lower cover like that one time which was rubbing on the belt on the inside of the cover.

[threecaster]

well cool!

I tend to be "overprotective" of my baby, at least when I have a wrench in my hand...Driving is a different story!

Maybe I'm noticing the chuttery sound cause I have no other pumps or anyother noisemakers hooked up....does not sound ugly or anything....just a new sound...

In regards to tension, I agree the book is less than precise. My main guide has been as to if I can fit the lower shroud into place; if the tensioner is too loose, it interferes with the shroud. So that at least indicates a ballpark area. I think I have it where it just clears the shroud.

I do have all the fasteners for the Lower (and upper) shrouds in place, but your comments make me think...

Perhaps I'll just remove the shrouds completly, re-install the lower pulley, and see what that sounds like.

Here is some other utter foolishnesss:

Right after I got the head back on, and the essential accessories, I fired it up to just to see if it ran. Now keep in mind, I viewed ALL of the pulleys as non-essential. (You may be face-palming about now...)

Started it, it ran great! (but no coolant, and battery only, I just let it run for a minute. Then shut it off.

At this point I look and say: "My timing belt acts like it's trying to come off..." about 5mm was sticking off of the cam cog.

Didn't think too much about it untill I went to install the main pulley, and then realised that IT HELPS KEEP THE TIMING BELT INSTALLED....

I am damn lucky the belt just didn't go FLINNNNGGG! right there in my face....the little flanges on the tensioner were the only thing keeping it on.

So let this be a lesson to you kids: When the book says "Temporarily Install", that mean use the bolts, and don't just stick it up there!

Maybe the old belt broke cause it felt it was being dis'd...("Fine! I see how you are....treat me that way I'll just leave!")

Let you know what I find out....

EDIT: maybe it is the interaction between the edge of the timing belt and the main pulley that is making the whining sound...as the belt is encountering the rounded edge of the pulley, it's making a rubber-on-metal squeaking sound, and when at speed makes for a whine...

Just wondering if this is normal, or should the belt stay centered on the cogs on it's own?

[threecaster]

HUZZAH!



Bring on the dancing girls and let the fun and festivities begin!

I sincerely thought *all* of the VW motors were (at lest like 1.8, 2.0, etc) were interference design motors. Since the 1.8 will spin freely, that makes me happy!

Now:

Compression: #1: 185psi #2: 187psi #3: 186psi #4: 185psi


Removed shrouds and re-installed lower pulley. Whine definitely from lower pulley area. Intensity of the sound is proportional to RPMs.

Loosened tension on belt to about 1/2 of what it was; right at the point where the floppyness goes away, but before tight-tight sets in....(about as precise as Bentley on this they are also...)

Whine seems to present an overall decrease.

Rubbed a little motor oil on 1/2 of the belt (just on the pulley edge)

Whine seems to ocillate, possibly confirming "belt rubbing on pulley" theory.

Further examination of the reverse of the Main Pulley shows high polish and even slight wear of the pulley, in perfect profile of the crank sproket. I think maybe every timing belt on this car has behaved this way.

Carve away some of the ribs inside of the plastic shroud to clear the new position of the tensioner.

That out of the way, it seemed overall rather happy with the state of things, so I put it all back together and drove it around the block a couple a times. So far so good.

I keep getting a bit of burning rubber smell, which makes me think the belt may last 500 miles.

Feeling determined (with phone in pocket) I trek up the interstate and rally around the B-roads for about 12 miles. The things sounds like it's got an extra pump now. (Or maybe a little turbo!)

Get home and pop the hood. There's the smell again. I stick my nose to the cowling, but can't quite get it. I decide an inspection is merited.

Removing the upper shroud from the belt, well it looks pretty nice. Some definite wear on the pulley edge, but nothing dramatic. Ever so slight track in the middle from the plastic shroud (maybe). I suspect some precision application of graphite may be quite telling...("Did you know he actually installed a PENCIL as part of his engine?")

But now I'm like WTF? I start poking around looking for hoses and leaks and find.....

A STYROFOAM CUP ON THE EXHAUST!



I had used it early on to catch some coolant, and I guess it fell back there and got forgot about....

So I think my little car is rarin to go!

And I'm a cappy hamper!


Edit: And WaterWheels, thanks for the encouragement....I could have gotten myself back into a real mess if I had gone crazy from this mess...

[antichristonwheels]

8V is a non interference mill. no worries if you snap the belt.

16V, 1.8T, and diesels are interference.

[Glegor]

if your timing belt is trying to WALK OFF THE PULLEYS, then you have issues, like a worn IM shaft bearing..

you SHOULD NOT need the belt shroud to keep it installed.. IDK how many people REFUSE to use the timing belt shroud.. and their belts NEVER come off, except for when a chunk of gravel gets caught in there, and breaks the belt..

if your belt is walking off the pulleys, you have other issues. thats what caused the first belt to break.

either your belt is not installed all the way, or its too loose, or your IM shaft bearing is TRASHED.

trust me tho, the timing belt cover DOES NOTHING IN TERMS OF locating the belt, it just covers it, and keeps debrits from damaging the belt.

again, the timing belt should not need ANYTHING to keep it running straight and true.

did you replace the TIMING BELT and TENSIONER? or just the belt?

did you wiggle the IM shaft at all, to see if it has play? if your belt was too tight, it probably damaged the outter IM shaft bearing

[Glegor]

and since you rubbed oil on your timing belt, you should replace it AGAIN.. oil and timing belts DO NOT mix.. it makes them weak, and break.

and you can either rotate your tensioner CCW to tension the belt, or rotat it CW to tension the belt..

if you tighten the tensioner CCW, it will make the timing belt rub on the lower timing belt cover

if you tighten the tensioner CW, it brings the belt away from the shroud, and actually engages a bit more teeth on the cam sprocket..

there is a CORRECT DIRECTION to tighten the bent tensioner.

is the tensioner BRAND NEW, ZERO MILES?

[threecaster]

You're half right....i suspect you somewhat misunderstood...

I ran the thing with the shroud completely removed, to try and determine the source of the noise...

It's actually the main pulley on the crank that is keeping the belt on, and apparently has been for some time...

Similar thoughts have crossed my mind. I do notice the area around the intermediate shaft seems to have a small sludge collection. But other wise the sproket is tight as a drum.

And tho the tensioner seems copacetic it's gonna get changed soon anyways.



Aha! Excellent point sir!

I definitely tightened my tensioner in a CCW direction, never even occurred to me to go the other way (I try to RTFM, but it's a big book!) Bentley actually specifies CW, somehow missed it.

Will correct that later today...

and I know oil and rubber don't mix. I only applied a small drop of Marvel Mystery Oil to the end of my finger, which was then applied to the edge of the belt. If this starts a chain reaction which forces some some fractalline progression of unlinking the sulfur molecules, then yes, I'll get a new belt.



And thanx for the direction correction!

[Glegor]

but you only replaced the belt? you didnt replace the tensioner?

thats NOT SMART AT ALL..

usually the tensioner is the piece that fails, and takes the belt out..

and yes, the crank pulley definitely locates the belt on the sprocket, to some degree.. its supposed to. the tensioner also keeps the belt from going anywhere, because of the lips on the outer edges..

[threecaster]

Well, the not smart part was me adjusting the tensioner the wrong way.

It was working fine when I changed the head gasket, but the fact that I've adjusted the timing somewhat and who knows what other variables merits a new tensioner, which will be here in the morning.

The one that broke only had about 15K on it...

But the fact that it's polishing the main pulley says something is tilted...

[threecaster]

Things just keep getting better. (and I mean that!)

New tensioner on, and properly adjusted this time; she sings like a sewing machine.

The new whine is still there, but is about 25% of the intensity of what it was when I first put everything back together. So not entirely sure what is behaving differently than from before.

Actually, speaking of, there is a change - in the timing.

I've never had any luck getting the notch on the main pulley to line up *exactly* with the intermedate sproket, like Bentley shows; I'm always 1/2 tooth off either way.

Before the gasket went I was running it with the notch forward (think crank CW about 2 deg) and it was quite aggressive in acceleration, but my mileage tended to run in the low 20's. My best bud in a 1989 was getting 38 mpg, and we have the same chips.

Now, I'm running it with the crank notch aft about 2 deg (one tooth CCW) and she seems to accelerate more smoothly. Rarely pings the valves. I've tweaked the distrubutor and I think I'm running it at about somwhere between 6 and 8 deg BTDC.

She did have a hard time starting, almost like premature ignition or something, but maybe not scince I tweaked the diff...

Can't find my timing light BTW...

Maybe I'll make one with a clothes pin and and LED...



I feel confident now, in just how she feels and runs, that she'll run just as far as I want her, at least untill something else breaks!

[WaterWheels]

The new whine is still there, but is about 25% of the intensity of what it was when I first put everything back together. . . I've never had any luck getting the notch on the main pulley to line up *exactly* with the intermedate sproket, like Bentley shows; . . . Can't find my timing light BTW

I'm not faulting you as your doing it seems what you can with what you have (seems to be not a lot). But first, buy a timing light. Even if you have to drive the car careful for a little while to get the cash, buy a light and if you can one with an advance function. There is no future in working on engines, for fun or profit, without a timing light to set the ignition timing. A few degrees can make a difference in a few things and "by ear" or using a light while turning the distributor just is not good enough.

The notches will never line up perfectly. Pictures with things set in the perfect position or drawing made that way are for reference only. In the real world things tend to move a little or are not made with as much precision as to work in an exacting way. Once all the marks are lined up as perfect as humanly possible, putting tension on the belt will cause them to move as things rotate a little. Can't be helped. It is only important that they do not move more then ONE (1) tooth. One tooth is the minimum adjustment you can make without an adjustable gear.

About the whine. Have you removed the v-belt(s) to see if the problem lies with them or what they drive? Have you tried backing off the timing belt tensioner a tiny bit to see if it changes or vanishes? Have you done some research into trying to locate just where it is comming from? An easy way, but be very careful, to track down noise location is by using a long screwdriver. Place the handle end to your ear and probe with the tip, but watch yourself in areas that have moving parts. Also don't wear any loose clothing.

[threecaster]

LOL!

I have a 28" piece of 1/2in (umm...80cm x 12mm) steel stock for just such purposes. Scares the hell out of my relatives when they see me do it.

It is quite fascinating to hear the sound, I just can't hold the thing on some spots for very long.

Yea, I'm all about instruments, when they can be had.

I have a concrete floor, and it is simply magical the way a wayward nut simply lays there in plain view upon such a thing. You may can understand how a deep appreciation for such a thing may come about

Yes, I'm not kidding about building a light. The components are actually more within my grasp than going out and $$ on a tool. I'm coasting on previous prosperity, and building up for the next endeavors.

The sad part is, I'm actually doing well off compared with some in my area. I have the luxury of feeding myself AND my little car.

But I agree, she seems a little underpowered now, and definitely needs tweaking.

Hmmm...there is a flea market...maybe $ instead of $$....

But yes...I try and sit and "see" all the parts working together and understand where the ignition is occuring at each cycle. So yes, one tooth is all I dare.

I've run her naked with only the pulley and the belt (sans v's & shroud) and played with the tensioner; I adjusted it as loose as I dare and it's there at the the higer rpms.

Now that I've driven it a few days, it may be genuinely getting softer. hard to say, I could just be getting used to it.....

My theory is the belt is polishing the pulley (as can be seen by wear on the reverse) and causing the "squealing". (just a different pitch than v-belt squeal)

With the new tensioner, it seems livable to me, but...my opinion may not hold water!

Time will tell all...

[Glegor]

LOL!

I have a 28" piece of 1/2in (umm...80cm x 12mm) steel stock for just such purposes. Scares the hell out of my relatives when they see me do it.

It is quite fascinating to hear the sound, I just can't hold the thing on some spots for very long.

Yea, I'm all about instruments, when they can be had.

I have a concrete floor, and it is simply magical the way a wayward nut simply lays there in plain view upon such a thing. You may can understand how a deep appreciation for such a thing may come about

Yes, I'm not kidding about building a light. The components are actually more within my grasp than going out and $$ on a tool. I'm coasting on previous prosperity, and building up for the next endeavors.

The sad part is, I'm actually doing well off compared with some in my area. I have the luxury of feeding myself AND my little car.

But I agree, she seems a little underpowered now, and definitely needs tweaking.

Hmmm...there is a flea market...maybe $ instead of $$....

But yes...I try and sit and "see" all the parts working together and understand where the ignition is occuring at each cycle. So yes, one tooth is all I dare.

I've run her naked with only the pulley and the belt (sans v's & shroud) and played with the tensioner; I adjusted it as loose as I dare and it's there at the the higer rpms.

Now that I've driven it a few days, it may be genuinely getting softer. hard to say, I could just be getting used to it.....

My theory is the belt is polishing the pulley (as can be seen by wear on the reverse) and causing the "squealing". (just a different pitch than v-belt squeal)

With the new tensioner, it seems livable to me, but...my opinion may not hold water!

Time will tell all...

are the BELT and TENSIONER both new? if you replaced one without the other, you are playing russian roulette..

[threecaster]

yes....they are both new now. (or both now new!)

For about three days, I ran it with the old tensioner, but this made me rather uncomfortable.

So now I have new belt and new tensioner.

And a friend up and gave me their old timing light (Montgomery Ward - when was the last time you saw them!) as he only mechanics aircraft now.

Not had a chance to check it, trying to get the clutch changed in my truck....

Will report back with timing results, and resultant effects on the whine...(if any)

[Jesse-B]

No where in the Bentley does it tell you to tighten the tensioner ccw or cw.

[Glegor]

No where in the Bentley does it tell you to tighten the tensioner ccw or cw.

well, you tighten it one way, and it rubs..

tighten it the other way, more teeth on the belt engage the cam sprocket, it doesnt rub, and all is right with the world..

trust me tho, even if the bentley does not say to tighten it CW, you still must tighten it CW, or else the belt will rub (BADLY) on the lower timing cover..

[Jesse-B]

Well I just did mine, but decided to ditch the cover. Are a couple teeth going to make a huge difference? The car is running great!

[Glegor]

Well I just did mine, but decided to ditch the cover. Are a couple teeth going to make a huge difference? The car is running great!

couple teeth off time?

or a couple teeth missing off the belt?

either way, its not ok at all.. neither..

[Jesse-B]

I was just saying I tightened the tensioner by hand it went ccw. I am not running a cover. I guess I will re adjust the tensioner.

[Jesse-B]

I was just saying I tightened the tensioner by hand it went ccw. I am not running a cover. I guess I will re adjust the tensioner.

[threecaster]

oh yea, It'll run fine with the tensioner CCW, and it does not seem to mind not having the extra grip on the cam...

but ifNu wanna be doing it more right, then CW is the way to go, and Bentley does say which direction, but it only says it once:

(From Bentley Stock No. VG92, editorial closing 03/92)

Section 3, Page 14, par 5 (#2):

{just below Fig. 4-4}

"Tighten the belt. Turn the tensioner clockwise and lock it in position with the locknut. Check the tension by twisting the belt as shown in Fig 4.5. ..."

s'ok, I missed it the first time too....

ran it for three days with it CCW.

But then changed the tensioner to a new one, and installed it in the manner recommended...

[Jesse-B]

Yea I ran it like that for a day. Then I corrected it.

[Mtl-Marc]

8V is a non interference mill. no worries if you snap the belt.

Shave the head to min thickness as per the Bentley to gain a higher CR, and it becomes an interference engine.

[ziddey]

How high does the CR go with that amount shaved off? Don't have my Bentley handy too see min specs.