3MZ-FE timing belt bent valves?

[Kurtatron]

I just nearly finished the timing belt on my RX330. I have some concern about the valves.

When I was trying to get the belt over the cam sprockets, the cam sprockets rolled 30 degrees clockwise and counterclockwise. This happened when I was struggling with the rear bank to align the belt.

The jumping cam sprockets happened when the crank was at TDC. The irritating cam sprockets kept wanting rotate out of TDC.

How likely is it I damaged a valve? I know this is an interference engine. Anyone have experience with this engine?

 

[mattd]

It should be fine

 

[Dave Sherman]

Chances are, it simply rolled off the peak of one of the cam lobes. The rear bank cam on my Pilot can do that, so if you bump it it may flip off the peak of the cam lobe. As long as you simply turned it back to correct position, you're fine. If you tried to do a complete revolution and forced your way through with a wrench, then you may have a problem.

 

[Kurtatron]

Chances are, it simply rolled off the peak of one of the cam lobes. The rear bank cam on my Pilot can do that, so if you bump it it may flip off the peak of the cam lobe. As long as you simply turned it back to correct position, you're fine. If you tried to do a complete revolution and forced your way through with a wrench, then you may have a problem.

Yes, that is exactly what happened. It jumped off the lobe peak. The instruction manual says you need to rotate the crank 60 degrees counterclockwise from TDC to avoid valve damage. After rotating the crank back to TDC to attach the belt. does that mean the risk returns? I wish the manual was more specific.

 

[The Critic]

After rotating the crank back to TDC to attach the belt. does that mean the risk returns?

Yes, but it's generally fine.

 

[Dave Sherman]

Seems like an odd procedure, usually it's moving the crank that's forbidden when the belt is off. Maybe that crank position is considered safe so the cams could be rotated completely without a valve bumping. Like I said, if you turned the cam back the way it came from, you're fine.

 

[The Critic]

Seems like an odd procedure, usually it's moving the crank that's forbidden when the belt is off. Maybe that crank position is considered safe so the cams could be rotated completely without a valve bumping. Like I said, if you turned the cam back the way it came from, you're fine.

 

[Hirev]

Should be ok. Next time try this.

 

[emmett442]

Rotating the cams are part of the procedure. I'm guessing that the 60 btdc position puts all pistons below the deck so that valve contact isn't possible while rotating cams.

I'm guessing it's fine. If the belt is on and you want to confirm it's ok before you continue, crank the engine. You'll hear the cylinder with the bent valve, if there is one. There'll be a "gallop" in the cranking sound.

 

[Kurtatron]

Rotating the cams are part of the procedure. I'm guessing that the 60 btdc position puts all pistons below the deck so that valve contact isn't possible while rotating cams.

I'm guessing it's fine. If the belt is on and you want to confirm it's ok before you continue, crank the engine. You'll hear the cylinder with the bent valve, if there is one. There'll be a "gallop" in the cranking sound.

Cranking with the starter or by hand?

 

[Exhaustgases]

You'll know when it runs.

 

[berniedd]

This scenario reminds me of how I learned to mark the critical moving parts before removing anything. I position the timing marks on all pulleys as per the manual, then dab white nail polish slash marks on the cams and crankshaft teeth, and then the corresponding timing belt locations. I remove the old belt, and apply same marks on the new belt. Voila! The new belt is installed correctly with all white marks lined up.