Timing belt skip

[MikeW]

Hi,

today I was about to initialize my new clutch. I was lying under the car and turned my engine (counterclockwise) by hand and heard suddenly a popping noise coming from the direction of the timing belt.
My helping collegue meant the noise perhaps came from the A/C compressor belt which probably has scratched on one of the disassembled suspension parts (lower control arm), - but to me it sounded more like the crankshaft has skipped one or two tooth.

Is that conceivable?

Regards Michael

 

[menappi]

Could be, I've actually had a timing belt skip on me while driving, I didn't tighten the tensioner enough. The easiest way to tell would be to reset the timing. Sometimes in those cases you can bend a valve, but if you were turning it by hand I doubt that would be a problem.

 

[drew]

it is possible (counter clockwise, from which view?) and not unheard of.

it is easy enough to check the timing belt alignment
--set the crank and verify the cams are on spec...adds a couple more hours to the project
-- remove the spark plugs and if you can rotate the crank easy by hand for a few turns (I can't remember the ratio between crank and cams). If it doesn't stick on a few rotations then take a compression check....if the compression is within spec: you are good.

Drew

 

[MikeW]

Thanks for response,

I turned the crank with the tranny off the engine by hand on the flywheel and did not feel any resistance of valves meeting pistons. I turned it in both directions clockwise and counterclockwise and I guess the popping-rubbersqueaking noise were when I turned it clockwise from the view of the tranny side. But I could be wrong and it was the other direction I am not sure anymore. It doesn't cost's me lot of strength to turn the crank while the noise occurs.
Just sitting in office and cannot check..is there a mark on the pulley for the TDC or do I need to remove the pulley and the lower TB-housing to set the crank on TDC?

Ah, Drew, you are right, timing is a crucial factor for the compression, good way. Thanks.

Regards Michael

 

[TheDeej]

I had recently had this problem on one of those 2.0L Supercharged Ecotec Cobalt engines, except i didn't hear it. The gear skipped a tooth without anyone detecting it. When we started it up it sounded a little funny, no parts contacting, just the exhaust note was off. Put it up on the dyno and sure enough we were down about 15 HP. Good thing you caught it before getting everything back together. :biggrin: