Timing Belt Broke

[seeodywhy]

My timing belt broke as soon as I arived at my house. It started making crazy noises. I know that they have interference engines and I was ready to start looking for another head. Most of the posts I saw said that there was a 50/50 chance. I figured that since I drift to my house as soon as I get into the parking lot my chances are a little better. I went and got a timing belt. I've seen posts on here about parts stores never having the right timing belt and to get the SI belt. The belt they had listed for the VX had the same part number as the SI. My girlfriend tries to start the car in the mean time and it sounds horrible. Nothing but pistons and valves duking it out. I put the timing belt on and it was too loose. My stupid a$$ tries to start it any way. I was trying to see if the valves were bent before it spent any money. I thought it was tight enough to to at least check. By now I figured out that a leaking water pump was responsible. I had my brother try to start it. The sound was terrible. It just slipped over the crank pulley. A neighbor could here it a few doors down. He said it's really over now. I ordered the timing belt water pump crank and cam seal idler pulley and the grommets for the spark plug wells and the o2 sensor on ebay for about 170 dollars. Long story short it runs better than ever after I put the new belt on yesterday. I have an HF to VX swap. I was getting about 35 with lots of hesitation in lean burn. The new o2 cured it. The old timing belt had to have been stretched too.

[GasSavers_Erik]

I have never seen a broken timing belt (thankfully).

What did the failure look like? Was it all frayed and stringy? Or was it a clean break between two teeth? Did the whole belt have lots of little cracks between the teeth?

[bowtieguy]

because many of us are cheap here, myself included, it has been well documented that we let certain maintanence items go extended intervals.

that said, THIS IS NOT 1 OF THEM! this is in the same catagory as brakes IMO.

i've always driven cars w/ timing chains, but when high mileage and/or performance falls (beyond the issue of tune-ups), i start thinking about getting the service done.

[Nrggeek]

I had the timing belt go in my '86 Civic Si. The idler pulley seized and the belt melted itself. It was a black gooey frayed mess. Valves were bent so I replaced them, but I don't think I tensioned the new belt enough (or maybe left too much black goo in between the crank pulley teeth) and the engine died again a few weeks later. I've got three belts on the shelf to do my three Civics. What am I waiting for?

[seeodywhy]

It was a clean break. I always thought that when these things broke it was instant doomsday.

[VetteOwner]

it is on a interference engine (which what yours sounds like) non interference means the valves and be wide open and the piston at top dead center (all the way up) and there will be no contact between valves and piston.

in an interference engine it means the parts interfere meaning the pistons smashed the valves when it came up.

id be on the lookout for a new engine.

the head is destroyed and possibly punched holes in the pistons with your repeated starting attempts.

note for the future: when an engine dies and makes horrible clanking noises DONT try to restart it untill your extremely sure you fixed it.

[seeodywhy]

You must not have read my entire post. I put a new belt, water pump, and idler pulley. It runs great. I had that common problem with the excessive hesitation in lean burn. I put a new o2 sensor in it and I can climb steep hills in lean burn in third gear. It is an interference engine but you can never tell until you actually put a new belt on it. Your right though it sounded horrible when it broke and both times I tried to start it. I guess I got lucky.

[VetteOwner]

i dont see how it didnt bend a valve if it truley is an interference engine.

unless it just jumped a tooth and ran like crap (what sometimes happens, a tooth beaks off and the belt is ok just slips and really screws up the timing)

[GasSavers_Erik]

It is possible that no damage would occur if none of the valves were all the way open when it broke/the cam stopped moving.

It is an interference engine in the sense that a fully open valve would hit the top of a piston.

So, the best position for the cam to be in when it stops (timing belt breaks) corresponds to TDC on any 2 of the four cylinders because: 1 cylinder would be at the top of a compression stroke ready to fire (all valves closed), the other cylinder at TDC would be ending the exhaust stroke/starting the intake stroke (both valves near closed). As for the other two cylinders at BDC- one would be finishing the power stroke with the exhaust valve just starting to open. The other BDC cylinder would be finishing the intake stroke with the intake valve almost closed.

It is all a matter of luck as to where the cam stops when the belt breaks.

I wonder if there is a better chance of not hitting a valve if the rpms are low when it breaks (maybe the camshaft is more likely to come to an instant dead stop rather than turning another 1/4 turn or so due to its momentum as might happen if the engine is at high rpms when cam momentum would play a bigger factor).

Of course, even at low rpms, if the belt breaks when a valve is fully open, you will bend it.

[seeodywhy]

I am pretty sure it hit a couple valves. But you're right. I was idling when it broke. Right when it broke it sounded like crap for a split second. I went and bought a 2002 civic coupe because I thought it was toast. Do a search on honda tech. When I installed the wrong belt at first it started for a few seconds and stopped when a piston made contact. I think that when the engine speed isn't high it may be enough to stop the piston without bending the valve. Now I am trying to sell my civic. BTW, anybody who has the lean burn hesitation problem, get a new LAF. I put the timing belt on and a new laf and it cured it. I tried to turn the cam by hand and it wouldn't turn but it would move backward. Presumably because it was in contact with a piston.