Question. I was driving and my car shut off. My car is a 94 honda accord at 400k. I was thinking the timing belt may have broke, but when I took off the valve cover and turned the engine by hand, the timing belt and camshaft pulley did turn as I moved it. But I noticed the camshaft itself was not turning. The bolt to the camshaft seemed to be loose as I was able to turn it by hand without a wrench.

Do I need to just tighten this nut? (Assuming that i have everything back at top dead center? Sorry if this is newbie post, ive only replaced a timing belt once on a civic and that was 10 years ago.

 

Damaged cam keyway or snapped cam. Only one way to find out, remove the cam gear.

 

So, it looks like the keyway "disentegrated" into two pieces.
Is there a way to check to see if my valves got damaged without taking the head off? Ie can i replace the key and turn it by hand or is there some other method?

 

Oh man, of course now the camshaft is completely out of synch with your crankshaft. This car probably has an interference engine and it is likely that valves got bend to some degree as you already know. I had a relative that had a BWM M3 and the camshaft snapped on him (camshaft was a two piece setup with bolting flange; the bolts failed) during highway driving and from what I remember 3 valves got bent. Looks to me that a snapped keyway is no different than the camshaft itself snapping in terms of its effects on the piston valve meeting.

Good luck, but who could have foreseen the keyway going out...not something to be thought to replace as preventive maintenance...uh? Then again, with 400k (miles?) and 25 years, that's a fantastic track record in and of itself!

I think one way to check for bend valves is to do a compression test for each cylinder. Apparently, one way to go about this is to do a wet compression test (wet as in dripping some oil via the sparkplug opening to help seal the piston rings). Because cranking the engine by hand is so so slow compared to engine running that it can be hard to get good compression test as there is too much time for it to leak out. Thus, sealing the piston rings with oil can significantly mitigate this leakage, right? Thus, the wet test is the way to go and if there is a bend valve somewhere or two there should be noticeable compression differences between cylinders. That is, if not all the cylinder have bend valve(s), so that you can compare between cylinders; between one that has a bent valve and one that does not.

Is it possible not to have any significantly bend valves if the camshaft goes out of synch with crank while driving on an interference engine?


Dave

 

remove the rocker assembly (keep the bolts in the assembly) to close all the valves. pull the spark plugs out. blow compressed air into the plug tubes. you'll hear rushing air from the exhaust (even at the tailpipe) or intake (from the throttle body) if valves are bent.

a sheared key and an intact belt suggest oil starvation at the camshaft. when you have the rocker assembly up, have a close look at the cam journals for any scoring or heat damage. plan on replacing the head if you find anything abnormal.