timing belt broke while ilding

[mikeesho1]

Hi my name is mike im sorty new to the dsm i prevously owned a 95 eclipse rs 420a i sold that car and bought a 95 talon tsi which i have only owned for 1 month so im slowly learning all of the problems with the car. I decided to check the timing belt i took the inspection cover off and found that the belt was starting to shred and looked like it was going to fall of so i started the car and watched the belt move back and forth and then it came off. I dont know what to think what kinda of damage was done if any like i said it was only idling

Does anybody have any thoughts on what i should do first

 

[WeaselHack]

thats horrible. IF your not already, you about to become a mechanic.

You probaly have bent valves, damaged pistons, and need your head resurfaced, and the block could be dmaaged, but , probaly not.

Start wrenching. I would start by pulling that head off and inspecting for damage.

Yes, very horrible news! Sorry

Let this be a lesson for others. Check your timing belt frequently and never, ever, ever run with a damaged belt!

Frankly I don't see the harm installing a new timing belt and performing a compression test to get an idea on the status of the engine before you start pulling the head and thinking about machine work. You really don't have anything to loose at this point. Perhaps now is a time to start thinking about a 6 bolt swap.

Regardless of what you decide you will likely find that a failed tensioner was the culprit.

 

[scott91370]

Lol, its non-interference, If anything he will cause more damage man, I think you should just DONT CRANK IT AT ALL. Pull that head man. You don't want to make it worse.

You mean that it IS an interference engine, right? If it was a non then it wouldn't be an issue.

 

[scott90gsx420]

Lol, its non-interference, If anything he will cause more damage man, I think you should just DONT CRANK IT AT ALL. Pull that head man. You don't want to make it worse.

YES it is an interference motor..

But seeming it was idling there is a VERY good chance it didn't do any damage.. The issue is when your going down the road,it snap's, then the wheels turn everything up to the tranny which turns the crank and causes the pistons to keep moving and slap the valves.. Seeming it was not rolling none of this would have happened.. The motor would just dye and everything would stop virtually instantaneously.. Therefor no contact would be made or VERY little and the valves and pistons would be ok..

And IF it made contact and SOMEHOW damaged them it wont be enough to hurt anything if you start the car back up.. As long as it is perfectly realigned then the motor will 1)not start..2)will start and run like crap)3 will run good and itll be like nothing happened.. If 3 is what happens still preform a compression test just for safety..

I say realign the motor and start her up youve got really nothing to loose and i highly doubt any damage was done..NOT TO SAY IT COULN"T HAPPEN AT IDLE BUT ITS VERY UNLIKELY LIKE 98%CHANCE EVERYTHING IS GOOD..

 

[jrohner]

My Talon's timing belt stripped off its teeth at an idle at a stop sign and bent the valves. It's not that hard or expense IF you can remove/install the head yourself.

 

[mikeesho1]

Yes the motor stopped instantly so im thinking there may not be any damage or little damage at all Thank you everybody means alot to me seeing that im new to this dsm stuff

 

[WeaselHack]

Lol, its non-interference, If anything he will cause more damage man, I think you should just DONT CRANK IT AT ALL. Pull that head man. You don't want to make it worse.

Nonsense...4G63 = INTERFERENCE.

Assuming he follows the timing belt installation steps correctly, he will be turning the engine by hand to confirm proper belt tension and will feel any resistance in the rotating assembly which could give him an idea if there are any bent valves, piston damage, etc.

Yes, pulling the head and inspecting for damage is the BEST choice for most of us but its not the ONLY option.

I've personally witnessed belt failure at idle without any noticeable damage (no/nominal change in compression) and the car is still a strong daily driver 10k miles later.

If you're worried about cranking an engine that might have slightly bent valves then consider timing the engine and using compressed air/leak down tester to charge the cylinder rather than a cranking compression test.

 

[scott90gsx420]

My Talon's timing belt stripped off its teeth at an idle at a stop sign and bent the valves. It's not that hard or expense IF you can remove/install the head yourself.

Seems like this would have allowed the motor to keep moving though.. Thats why it bent the valves... Im going to take a stab and say only intake or exhaust were bent not some on both sides?? Could be wrong haha but thats why i would assume the valves got bent in this case..

Nonsense...4G63 = INTERFERENCE.

Assuming he follows the timing belt installation steps correctly, he will be turning the engine by hand to confirm proper belt tension and will feel any resistance in the rotating assembly which could give him an idea if there are any bent valves, piston damage, etc.

Yes, pulling the head and inspecting for damage is the BEST choice for most of us but its not the ONLY option.

I've personally witnessed belt failure at idle without any noticeable damage (no/nominal change in compression) and the car is still a strong daily driver 10k miles later.

If you're worried about cranking an engine that might have slightly bent valves then consider timing the engine and using compressed air/leak down tester to charge the cylinder rather than a cranking compression test.

what this guy said gents..... He knows what im saying haha.. The idea about cranking it by hand to the OP if you do this then make sure the spark plugs are out or else youll be fighting the motors compression by hand and itll feel like something is resisting you..

 

[fourgsixthree33]

I think it's worth a shot. I would just buy new belts and tensioners (as you are going to need them anyway) and install everything while doing some tests and checking stuff out.

My gf snapped her timing belt in her tsi awd going 65mph down the highway. Slapped a new belt on it and she ran great for another 20K.

You very well could have bent some valves. While damaging anything other than the valves from a timing belt failure at idle is unlikely, it's still possible. You wont know for sure until you do something.

Pull the head, or put a belt on it and fire the b*tch up. I don't see how you could do any more damage if there is any damage right now at all.

 

[99gst_racer]

Sounds like it wasn't tensioned properly.

 

[1stgenracer1993]

totally agree, get new t belt and tensioner put it on and turn it over by hand, your gonna know imediately if its really bad, and if those results are good step up to the compression test. if all is good your in the clear if not and you do the work yourself the belt and tensioner are still reusable. just my .02

 

[99gst_racer]

If it were mine, I'd pull the cams and do a leakdown test before even bothering with another timing belt...

 

[scott90gsx420]

O IM SO SORRY!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! I meant it IS A INTERFERENCE MOTOR. I mean the description should have explained my error. Cause I said it will BEND VALVES and etc. Sorry guys.

As far as the belt breaking, Regardless if it was in neutral, that Piston still went flying upwards to TDC, the valves may have stopped but that crank has that big old flywheel. If you don't want to pull the head, a leakdown test would be best. But personally I would just pull the engine and go from there.

ya that's why you can hear the motor spinning after you shut it off huh?? haha it stopped bro. The weight of the pistons/rods are more then the flywheel.. Not to mention the crank and force of resistance on the bearings bla bla bla... I can argue physics with you all day but the only thing that matters is that they DID NOT make contact

 

[WeaselHack]

I just built my 7 bolt.... My flywheel is for sure almost as heavy then my entire rotating assembly including the crank...

WRONG AGAIN! How heavy is your flywheel? In excess of 40LBS? I don't think so...

EDIT: Hard numbers for you:

Stock DSM Flywheel weighs in at roughly 19lbs and last time I checked nobody makes a heavier flywheel.
Stock DSM Crank weighs in at roughly 40lbs. For reference, the Manley knife edged billet crank weighs 36lbs.

You do the math

 

[g4ebguy90]

..... You guys are right. I shouldn't have gotten mad at put up some false opinionated answers, regarding rotating assembly weight vs flywheel.

 

[WeaselHack]

Dude, I was kinda being sarcastic in that last statement, I will admit the crank is heavy, 40 lbs seems excessive to me but sure. It's been a while since I installed mine. The flywheel yeh is around 20 lbs. The pistons and rods i'd say are about 5 lbs per cyl. But I'm sure you will dig that number up to.

I will admit that the rotating assembly is heavier then a flywheel. But honestly with the crank having couterweights I think it makes even more sense that it rotates when it shuts off. It has kinetic energy.

My point was, the flywheel helps the engine continuing to spin. So yeh when you shut off your car, it's gonna spin for a sec or 2 at most.

Anyways I deleted all the comments. You guys are just looking for stuff to argue about. So I'm done attempting to help this guy. You guys can.

Good Luck

Interference Engine-Belt Breaks=
I have heard of lucky people getting away with it, Idk how thats possible but it is.

Look, no disrespect to you and my apology to the OP and subscribers for all the clutter however none of the information you've provided in this thread is even remotely accurate.

Its not about ganging up on you or anyone else for that matter but if you continue insisting the sky is RED I will keep reminding you that its indeed Blue!

The main function of a flywheel is to maintain a constant angular velocity of the crankshaft. The counterweights on your crankshaft minimize vibration. Yes, the flywheel is a rotational energy storage device but the friction of the piston rings against the cylinder wall coupled with the percentage of closed valves (after his timing belt broke) will stop the crank almost instantly.

And because you asked and it is indeed valuable information I found the following for whoever may be curious:

1G Rods: 1.53 lbs each (no bearing w/ end cap and bolts)
1G Piston: 0.80 lbs each (piston only, no rings or pin)
6 Bolt Crank: 35.78 lbs

So minus bearings, rings and pin your entire STOCK 6bolt rotating assembly weighs in at: 45.1lbs

Enjoy!

 

[g4ebguy90]

Its actually a 7 bolt so weight will actually be less. I assume due to the rods being lighter the 6 bolts.

When I made the comment about the crank, I might have been being a little on the stretching the truth side. But I don't remember my crank being actually that heavy. I can't believe my crank is 40 lbs, Unless the 6 bolt is heavier then a 7 bolt crank.

But if you remember,

That one guy said that the rods and pistons alone were more heavy then the flywheel, which is false.

The weight of the pistons/rods are more then the flywheel Scott90GSX said that.
Complete false comment. Thats when I said that my rotating assembly weighs almost as much.

So seriously go spit at him.
As for the couterweights on the crank, I think it does alot more cancel vibration then that for the throws of the crank.
As for the rings slowing down the engine instantly, That is false itself.
I can put a ratchet on my crank pulley and just from the compression it can throw itself at least a quarter turn. So with the engine running I would assume it could do more then that. It's already spinning at 800 rpm or so.

So what I just noticed is that, I, today literally ripped out my rotating assembly besides the crank. I held the rods and pistons in my hand, the flywheel I have for my 7 bolt is heavy as heck.
I don't weigh every single thing that I pull out of my engine. Are you going to weigh the bearings to and throw that in my face, saying I am giving false information???? Rods and pistons felt very light i guesstimated at 5lbs per set. Give me a break dude.

 

[chino9656]

ya that's why you can hear the motor spinning after you shut it off huh?? haha it stopped bro. The weight of the pistons/rods are more then the flywheel.. Not to mention the crank and force of resistance on the bearings bla bla bla... I can argue physics with you all day but the only thing that matters is that they DID NOT make contact

It only takes one rotation for contact to be made. You can't say that when you turn off a car that it instantly stops in it's tracks. At idle, the engine rotates roughly 12 times. with 4 cylinders, you would have to have a 0 in 48 chance of making contact.
Personally, I wouldn't risk it. Pulling the cams and doing a pressure test sounds like a good idea. My .02

 

[g4ebguy90]

The guy above me pretty much made my point. Just without people ripping all over him.

 

[WeaselHack]

The guy above me pretty much made my point. Just without people ripping all over him.

Except what do YOU think is going to happen when a percentage of the valves are CLOSED because the damm timing belt broke? An engine out of time will not efficiently pump air if at all. A cylinder with closed valves isn’t going to want to compress or pull vacuum. That's right kids, if you cut off an internal combustion engine's air supply it will LITERALLY STOP INSTANTLY!

I will set the record straight once again:

The rotating assembly weight between a 6 and 7 bolt is within 2 lbs...

scott90gsx420's comments on piston/rod weight is true if running a lightened flywheel (which he is) or 1/2 the other members on this site who run the 6 bolt Findanza that weighs 8lbs...he was rather accurate.

You said "rotating assembly". RA = crank, rods & pistons....you were off by more than 50%

I'm not spitting on anyone...You simply continue to provide inaccurate information and assumptions while I’m providing facts...Simple as that. Nothing personal dude.


...and because I knew you would ask, the Fidanza flywheel for the 7 bolt weighs in at 8.5lbs

 

[g4ebguy90]

I don't see why it would stop instantly, there is no compression, besides ring friction whats there to slow it down. I think it would slow down even slower if the timing belt broke.

Dude you are seriously going overboard. Just stop.
I said ALMOST WEIGHS with being sarcastic. I know that stuff is more heavy then a flywheel.
No i meant my STOCK 7 BOLT FLYWHEEL.
You are not making a personal attack but you are seriously making this a rather pointless thread.
What you are saying is false to.

You act as if when your timing belt breaks, the engine just *for no reason* stops instantly in place. Which it don't mind you. I'm waiting for someone to chime in on that. Cause you don't seem to understand.

Just think about what you are saying.

Your telling me the engine is rotating at 800 rpm, the belt breaks, the valves are stuck in there position instantly. The rotating assembly however continues to rotate until the kinetic energy it has dissapates. So while the valves are open, the still MOVING pistons go up, strike the valves and that's about it. It only takes like half a sec. After the valves are bent, compression is then lost, making it take longer for the engine to slow down. As it's not using any force to push against the air pressure.

AM I wrong???? or are u?
COMBUSTION STOPS, but rotation doesn't.

Except An engine out of time will not efficiently pump air if at all. A cylinder with closed valves isn’t going to want to compress or pull vacuum. That's right kids

I really love this quote , A cyl with closes valves doesn't want to compress, HMMMMMM isn't that part of the 4 strokes........ haha

 

[WeaselHack]

You act as if when your timing belt breaks, the engine just *for no reason* stops instantly in place. Which it don't mind you. I'm waiting for someone to chime in on that. Cause you don't seem to understand.

The OP was at idle, 750rpm, when his belt broke. He has a very good chance that there was very little or no piston to valve contact. An engine can go from 750 rpm to dead stop very quickly....especially when its out of time. A 17lb flywheel does not carry the inertia to keep a 4g36 rotating like you seem to imply.

Everything I've said is true in the context of the OP's issue. He even said it himself. He was under the hood when it broke and "virtually stopped instantly".

You also keep forgetting that I've personally witnessed my friend's 4g63 timing belt fail at idle and the engine survived.

Meanwhile, you've been out in left field with "maybe this, maybe that", "IDK" and exaggerating making an engine out to sound like a ball bearing turbo that spins forever, is feather light weight and that a 4g63 is non interference...

 

[g4ebguy90]

No, I made a mistake putting in NON-interference. MY BAD typo DUDE, I even put under it about bending valves. So you need to drop that crap. No what I'm saying is that, your engine doesn't stop instantly LIKE you stated which is wrong. Even journal bearing turbos spin for a long time, as for the rotating assembly as i stated, he said rods and pistons, I know for a fact my rods and pistons don't weigh as much as a flywheel, you can include some weight from the crank also to make up for it.

Either way you still said, With valves closed a engine won't make compression .


I can't believe you are acting like a engine can't even go 1 stroke, when it dies at 800 rpm. It don't stop that fast bro.

750 idle is around 12-13 rps. So yeh bro.....
I'm off to bed. No hard feelings. I know we both know what were talking about. I'm a little grumpy from being tired. So see ya man. Good info. But you are also wrong on some parts.

 

[chino9656]

If you go out right now and turn on your car, and then turn it off, the engine will still rotate. Not for long, maybe a second or two. what makes it stop is there is suddenly no combustion occurring in the opposite-firing cylinders to continue to the rotation.
And if I understand what you are saying...that some of the valves will be closed. Sure. and the other half will still be open.
Some people get lucky and don't have contact. Some not so much. But the point we are trying to get across is that it is possible, and that OP should figure out if there was, not just assume that there wasn't. Better safe than sorry.

 

[jamezbennihanna]

I would put a new timing belt on and turn over by hand and see if when the pistons are up if there is any resistance. If not do a comp check if that's ok try to start. I'm with weaselhack the motor should have almost stoped dead because your valve train wasn't moving there for there was no air coming in when supposed to and out when supposed to. Basically it was trying to suck in air and couldn't and expel air and couldn't on some cylinders not all cause that would be impossible. But you do what you think is the right thing to do that's just my .02 .