running the motor after timing belt broke it will cause the cylinder crack inside?
Running the engine without the timing belt can cause a piston to smash into an open valve which will break it… that valve falls into the cyclinder and does all kinds of damage to the cylinder and other valve as it bounces around…
So the answer… not neccessarily… but it can.
if you have the stock b18a in your car and the timing belt “breaks” or “snaps”
all valves in the head will automatically go in the close position.
The chances of the valves hitting the head with the timing belt breaking in half should be at 0%.
unless you broke a couple of teeth on the belt and messed with the timing, like my belt did. but i was lucky enough to walk away without a bent valve.
but to your question, a broken timing belt shouldnt cause a crack in one of the cylinders.
-karlo
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The b18a is an interference motor, so valve to piston contact when mechanical timing is off is possible.
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In my experience valve to piston contact is very rare when you break a timing belt.
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Usually the contact is minor and just “bends” a valve. This causes it not to seat properly. Usually the valve doesn’t break and fall into the cylinder, I’ve never seen that actually unless somehow the keepers fall off.
Not to thread jack but is this statement really true
if you have the stock b18a in your car and the timing belt “breaks” or “snaps”
all valves in the head will automatically go in the close position.
No, of course it isn’t. If the timing belt were to break when the engine is running, both the camshafts would stop rotating at whatever position they were in at the moment the belt broke (plus whatever angular rotation they might have from the momentum of spinning). That could be at any position–all valves closed, intake valves open, exhaust valves open, etc etc. Honestly, why would someone think all the valves would automatically shut in the event of a timing belt failure?
i dont know i just wanted to make sure it wasnt true just askin anyway thanks
[QUOTE=iRockTheDA9;2090264]if you have the stock b18a in your car and the timing belt “breaks” or “snaps”
all valves in the head will automatically go in the close position.
The chances of the valves hitting the head with the timing belt breaking in half should be at 0%.
unless you broke a couple of teeth on the belt and messed with the timing, like my belt did. but i was lucky enough to walk away without a bent valve.
but to your question, a broken timing belt shouldnt cause a crack in one of the cylinders.
-karlo[/QUOTE]
Do a little reading before you spread bad info:
Now onto the big issue, Interference Engines… If your timing belt breaks, the engine will continue to turn, but the camshaft stops. If any of the valves are open, and your engine is an interference engine, the piston will slam into the open valve and cause some real expensive damage. Most modern engines are built with very close tolerances, and to squeeze every last bit of power into a small package, engine manufacturers sometimes create issues with clearances. The easiest way to find out if your engine is an interference engine, is to look at the following guide published by Gates, a manufacturer of timing belts. They include the replacement interval and whether you engine is an interference engine or not.
i go with experience, my timing belt broke and the valves did NOt hit the pistons.
after taking off the old belt and messing with the cams, it seems as if the lobes turned and partially closed the valves, technically not closing all the way, but the valves werent at 100% open.
you can try it for yourself, the slightest turn of the cam and the lobes seem to slide over and allow the valves to close slightly, that is without the timing belt on of course. so in the event of a timing belt breaking, the valves should close slighty causing the pistons NOT to hit the valves.
also, for the numerous posts ive read, people did NOT damage their engine from broken timing belts, so maybe what i posted isnt 100% false.
the statement i made, was just a bit exaggerated and i am sorry for that.
[QUOTE=iRockTheDA9;2090789]also, for the numerous posts ive read, people did NOT damage their engine from broken timing belts, so maybe what i posted isnt 100% false.
the statement i made, was just a bit exaggerated and i am sorry for that.[/QUOTE]
Its alright man we all drive DA’s.:manual::auto:
This is quite an amusing post. I might as well put my 2c in… G2 tegs are mechanical rockers. There are always 2 cylinders with valves open. As Colin mentioned they’re interference engines meaning there’s no room for error if the belt snaps or you get valve float. I’m sure it’s possible that people have been lucky and their car still runs even after their belt snapped but I guarantee it’s been set up for failure.
I would have to disagree. With stock b18a/b engines my experience has been that a broken timing belt or mis-timed engine has NOT resulted in valve to piston contact. It is possible since they are interference engines, but every case I have seen personally has been fine - just change the belt and/or properly set the timing and the engines were back to normal. I wouldn’t bet on those same odds w/ vtec engines, higher compression pistons, milling…etc
So our engines aren’t really interference… My understanding is that interference means kiss your valves goodbye when the belt snaps…
im sure he means the contact is minimal but there is contact.
our engines are interference engines… i’ve seen valves get bent from snapped belts. There are the lucky few where there’s no damage. Just because they were lucky doesnt mean you or anyone else will be. Just change it at the appropiate interval and take care of your engine. Dont take the belt for granted especially if you’re broke. =P…:read:
If a belt was too snap, yes, you could put on a new belt and do a leak down test. Or, just run it and cross your fingers. :rockon:
NO, that is NOT what I was saying.
NO, that is also NOT what I was saying.
The engines ARE interference engines, read up on that concept. It doesn’t mean the valves hit the pistons ALL the time. There’s only a certain period of time and specific amount of degrees of rotation in which interference would occur. The piston needs to be high enough up in the cylinder at the same time the valve is at or around fully open. Each different type of engine will have different specs, some will have a higher chance of valve to piston contact, some will have a lower chance. This isn’t rocket science so I’m not sure why I seem to be confusing everyone.
Like I said, my experience is that with STOCK b18a/b motors interference almost never happens. I’ve never seen it personally, only heard of it. I know it’s possible and not something to brush off lightly. However, if you have a stock b18a and break your belt I wouldn’t jump to conclusions. Do like 90_DA recommended, change the belt, do a leakdown test… And of course, don’t lag on changing the belt at the specified intervals.
We need a poll. Not to determine what our engines are, but to see how many people had any damage from broken belt while running. My experience an 70KPH caused no damage. I have seen at least one post where it did. But it seems like the majority of people who this happens to get away with putting a new belt (and water pump sometimes since your in there) and nothing more.
Can the recommended procedure be just change the belt first, before you tear down the engine for inspection?
[QUOTE=93IntegraGS;2092867]
Can the recommended procedure be just change the belt first, before you tear down the engine for inspection?[/QUOTE]
Yes, recommended procedure is:
- Install new belt
- Perform leakdown test
- If leakdown test is OK you’re done.
- If leakdown test indicates bent valves then you’ll need to pull the head off and do the repair.
You pretty much need the belt on there to do the leakdown test, and regardless of whether the valves are OK or not you’ll need a new belt. So might as well just get that stuff out of the way. If you pull the head to inspect the valves then you’re automatically in need of a $60 head gasket regardless of if there’s damage. No sense in wasting that money if you don’t need to.
I’m sorry if I’m upsetting or misunderstanding you Colin, I just can’t understand how an interference engine can avoid damage when the belt snaps. I have a very firm understanding of the 4 stroke cycle, and a firm understanding of the term interference. My definition of interference is at no time will the piston spare a valve if the cam stops turning while the crank continues. Unless the cam continues moving by momentum and manages to stay in close enough time with the crank to prevent damage, I can’t wrap my head around it. I’m making this statement only to learn, not to piss anyone off haha.
I’ve personally never had a belt snap on me while driving, although I have caught my belt half ripped through during a valve adjustment… Since I had a B20 I was waiting to put in, I snapped the belt on purpose and tried rotating the crank and it stopped. I was gunna put a new belt on but I couldn’t unbolt my crank so I got fed up and swapped my B20 in :roll: