Checkmarks

Is it possible for the camshaft to slip the timing sprocket?

The car was given to me and the cause of problem (from a woman's language) "It just overheated". Simple fix I say. Cut head check for bent valves and slap it together. Sure enough it needed a water pump, it froze up but for the bonus the valves did not get hit. That would have been a <$200 repair and back in service.

Now I noted another oddity, when the cam was aligned with all the marks the motor was at TDC compression stroke on the #3 piston. With all the timing marks aligned I had to install the distributor pointing at the #3 plug. This seemed odd but maybe that was a Honda standard.

$200 later and the car was back in service. Drove the car 500 miles and it was running as expected like a HONDA. (great car by the way) . Then all of a sudden the motor shut off and it lost compression. On the side of the road I verified the timing marks and they are in agreement (no belt busted or jumped teeth). The compression is 30-15-10-20 psi.

Tear down and the valves are bent. Straighten the valves with a hammer, was a little more gentle than that. The valve sealing was good, assembled again and turned over the motor with the ignition and IT BENT THE VALVES AGAIN.

Turn the motor over by hand (valve cover off) and while the Exhaust valve was at full open the pistons were at TDC.

Now to the point. I pulled the camshaft and looked at how the camshaft sprocket attaches to the camshaft. On the camshaft there is a woodruff key slot. On the sprocket there is no slot. In the camshaft slot falls out a piece of steel looked like it was forcing hold on the sprocket.


Is this how Honda manages the camshaft position held on the sprocket? Is this some BAD back yard mechanic's solution fixing a car so it WILL breakdown again and they get more business? Last question is there a woodruff key slot in the cam sprocket.

98civdx

Pics of the cam gear? There should deffinetly be a woodruff key there!

Without it, yes the gear can slip, throwing the timing off and causing you to bend valves.

My guess is this isn't first time this happened, and they hoobled it back togther and got rid of it. you know get the enjoyment of fixing it.

Checkmarks

Thank you for the response. Your help was greatly appreciated and as a note do not take your car to this mechanic!

slomofo

iTrader: (1)

That cam sprocket looks like it came off of an older D15 Civic. I don't think this car has been rigged before, I think the problem happened all on it's own. That particular cam sprocket never had a separate woodruff key because the key was part of the cam sprocket itself. Looks like the keyway just broke off and the damage happened.

I have an Accord right now where the exact problem occurred, but on this Accord the owner did his own head gasket job and swapped the timing belt, but kept the old waterpump & balance shaft belts. What happened to this car was the owner improperly torqued down the rocker arm shaft and the car ran fine until the waterpump seized, then a chain reaction occured where the woodruff key in the cam sprocket broke off as well as the camshaft breaking clean in half.

Checkmarks

Slomofo, I looked again with a closer eye and you are correct. It does appear the piece the piece busted off the sprocket and that was what remained in the key way. Looking at my picture above at approx 4 and 5 o'clock hour is the scar where the chunk came from. The scar occurs right above the round marking alignment dot.

Thanks men, calling out dubious mechanics did not sit well with me.

98civdx

By the 2 dot looking things? The picture is a bit too bright for me to see much.

I've never actualy seen a D15 cam gear, so I had no idea they didn't have a normal woodruff key.

Checkmarks

98civ,

Yes in the picture the two dot looking thing is the left and the right edge of the break. The woodruff key is a sort-a-like woodruff, however the locking key is built into the cam sprocket itself.