I installed a new water pump in my 92 accord LX. Replaced the timing belt and balance belt at the some time. Got it all back together and went to start it. It fired then immediately died. Turned a few more times and would do nothing. Looked in the oil fill hole and had a helper turn the key. No movement of rockers/valves. Pulled it back apart and sure enough, the timing belt was in 3 pieces. Any ideas what the heck could have caused this? My only hope is when I pulled the lower timing cover off, a 6mmx1 bolt fell out. I think it was the bolt that I locked the tension arm with. Although I removed it from the arm, it must have fallen behind one of the pulleys and I didn’t see it. Hoping maybe it jammed something or caused a lock to break the timing belt.

 

if the tensioning pullies spin freely and the belt is tensioned properly, there's no reason for it to break. If the belt broke while running, you may have valve damage. I'm not certain, but i think you have an interference engine. a new belt would be a waste of time if you have ruined the valves.

 

How can I verify bent valve/valves? Will I be able to tell by turning the cam? Counter clockwise, correct? How do you keep the nut from loosening turning counter clockwise? Could it being out of time cause the belt to break? Cyl 1 was top dead center, but couldn't it be TDC with valves open instead of closed?

 

first off, you shouldn't turn the engine with the camshaft. This eliminates the concern of loosening the bolt. turning the cam with no belt won't loosen the bolt. And, no , with an interference engine, the valve cannot be open at TDC. to keep from having to reinstall all the components, you can check cylinder leakage with a compression tester and air hose.

with timing belt OFF, set the crank position at 90 degress before or past TDC to get all pistons at half stroke and out of the way. DO NOT go thru the TDC position. if the position the crank is in now is before TDC, turn it back to 90 degress before TDC. if it's after TDC, go to 90 deg past. if it's more than 90 degrees past or before TDC, back it up or advance it, but don't go thru TDC on any cylinder. basically, just move the keyway in the crank to the nearest horizontal position, minimizing rotation. if you pass thru TDC, you may bend valves (if your valves are still good).

do this with the valve cover and timing belt off:

install a compression tester hose in the spark plug hole, set the cam lobes for compression position on #1 cylinder, then attach an air hose to the compression tester hose and pressurize the cylinder. do this for each cylinder.

if you have air flowing out thru the tailpipe or back thru the intake manifold, you have bent the corresponding valve. this may not be much air, so you may have to listen for a hissing sound. if you can't tell, you may need to pressurize the cylinder with an inline gauge and see if it leaks down quickly. if you have any bent valves, remove the head and repair it.

 

Then, I am guessing I must have a bent valve preventing the cam from turning easily. When turning the cam, (Timing Belt off) it takes a lot of effort to turn and then breaks the bolt loose. Way too tight to grab the pulley and turn by hand.

 

you should still be able to turn the cam. it is often too tight to turn by hand, but the bolt should still hold with a ratchet or wrench. if you don't have the pistons af half stroke, you may be forcing a valve into a piston. if you get the pistons at half stroke, you should be able to turn the cam no problem, even with bent valves.

 

Gotcha, Pistons weren't at half stroke. #1 @ TDC, must by why. I'll follow your steps. If my #4 was a TDC instead of #1 (Timing out 180) would that cause a timing belt to break? #1 cylinder is drivers side, correct? Thanks for the tips!

 

well, to be technically correct, TDC is the point at which the piston is at the top of its stroke, so that can also mean the exhaust stroke. when doing the timing belt job, is doesn't really matter which stroke you are on, just as long as you are at TDC on #1. the alignment marks are there based on being on the compression stroke, so that's why you do it that way (cam and crank both UP). you really can't be 180 off if you have the crank and cams vertical and aligned with the marks.

To answer your question, yes, you could break the belt if the pistons slam into the valves. it's possible, depending on how the piston hit and which valves were damaged, that the piston was trying to reverse the cam rotation by forcing the valve in the opposite direction that the cam is pushing it. this will create major tension in the belt and break it (if it doesn't skip teeth the first).

yes, #1 is on the driver's side (accessory side of the engine and counting toward the trans, 2,3,4).

 

I'm kind of confused then. Currently the car is sitting with both the crank and cam marks vertical pointing up and number 4 cyl is in the up position and #1 is down. I verified sticking a rod down the spark plug hole.

 

if the spark plugs are out of the head and no timing belt on and you still can't turn it over then you have something majorly wrong.

 

1 and 4 are always in the same position-same goes for 2 and 3. It's impossible for the number one piston to be down if you have the crank aligned with the timing mark on the block.

If you have the crank aligned with the timing marks and the cam aligned with the timing marks, pistons 1 and 4 are both at TDC, 1 on compression, 4 on exhaust.

your rod may be touching a bent valve on number 4 and the piston on 1, and it only appears that you have pistons in different locations. Make sure you aren't catching a valve on #4. get something flexible and try to work it into the cylinder further.

this is an interference engine meaning the pistons will hit the valves if the belt breaks. i'd check your pistons and timing marks again. also see if you have excessive rocker arm-to-valve stem clearance. that would indicate a bent valve if it's way out of spec (way too much clearance).

 

Update; Once I sat down and educated myself on this beast it all came together for me. I guess it was just a bad belt. Set all my timings and fired it up before complete assembly to make sure it worked right. All is well and it has never ran better! Also, the balance belt was broke when I first tore it down. Who knows how long I have been driving it with no balance shafts working! Thanks for all the help and pointers.