2002 XC70 bent valve possibility

[dikidera]

Of course I meant with the belt on.

But yeah the rules here have changed. Usually to get the harmonic balancer off you use an impact gun. This concentrates the power in a way that the breaker bar cannot. I can see how using a breaker bar with an extension pipe and using a lot of force + the crank lock tool slipping can put a lot of force on the valves. If you can see an outline then the force was indeed greater than it should have been for them.

[vtl]

Rotate the crank prior to putting on belt? Am I wrong in thinking you don't want to do that? I am fairly certain it is correctly timed right now, basically how it was before I took the belt off.

What happened is the crank lock I was using yielded from the force of the breaker bar and allowed the crank to rotate independent of the cams. At this point piston 4 contacted the intake valves at probably 40 degrees ccw crank rotation. I think it bent the valves here and went to probably 60 degrees ccw (as the ratchet/breaker came off the nut)

Looking at the position of the pistons/valves through ccw crank rotation I can only conceive of the possibility of contact of piston 4 with the intake valves. There is evidence of contact on the face of piston 4 intake side seen with a bore scope. The valves look fine and don't let any light through when in compression. Not sure why cylinder 1 would have a problem.

I am very upset about this, especially the deal with this crank tool. After if yielded I stuck a 3/8 ratchet extension in the hole and it held fine. Im still waiting on my leak down tester but man it's not a good night.

You can not damage the valve by hands. What you see on the piston is the recession factory made for valves.

Now, the engine may already have had compression problems due to various reasons, like

- no tappet/camshaft clearance
- valve face and seat pitting
- worn or stuck compression rings

[jimmydean012]

I wish you were right but I'm not so sure. I only see this mark on piston 4 and it looks pretty fresh.

[vtl]

What do you see? Something like this?

1.jpg (49.1 KiB) Viewed 460 times

[jimmydean012]

Kind of, yes. The driver side mark is more prominent and it catches light and seems like there is bare metal vs the carbon

[vtl]

Kind of, yes. The driver side mark is more prominent and it catches light and seems like there is bare metal vs the carbon

That's ok, the valve hit the piston after all and removed some of carbon.

[vtl]

To elaborate further: I've had my DIY camshaft lock tool snapped once and the valves smashed into piston while tightening the sprocket's big bolt at the required pretty high torque spec. No damage. I also accidentally dropped a valve to concrete floor - not even a nick or tiniest scratch on the valve. They are tough.

[jimmydean012]

Hmm, are you thinking the valves are still good? One thing that really makes me wonder is after the socket had slipped off the crank bolt, the crank was no longer locked at the timing mark and was probably 60 degrees CCW, and I was unable to return it to the timing mark without encountering valves. So this tells me the piston had to contact a valve and force past it to get to the position it was in.

I'm seeing weird compression values all across the head right now but this is only cranking it by hand with no leakdown tester, Amazon has delayed my order Maybe some carbon in the valve seats or something?

[vtl]

Doesn't matter what happened during assembly of the engine, you just can't bend the valves with hand tools. I know a couple of stories of the valves surviving the cranking by starter with angles way off and piston slapping into valves.

These are the reasons for no compression that I can think of: viewtopic.php?p=645714#p645714

And you can't really test the compression cranking it by hand. Have to do it with the starter. And if it sat for too long, you have to add oil to seal the rings.

[jimmydean012]

Alright... I was looking through some previous threads about bent valves and saw where you commented "If the valves hit the pistons even lightly they could be bent and leak air."

Is this using the starter or?