Vehicle: 2006 Vue 3.5L v6 (Honda j35 engine)
I was dumb/tired, and managed to rotate the crank clockwise a bit with the timing belt removed. I thought I'd just rotate clockwise until the timing mark lined up again, and I hit some real resistance after about 1/4 turn (spark plugs were not removed). Realizing my error with the cams not turning, I rotated the crank CCW back to the mark with much less resistance. What potential damage did I cause, and what should I be checking after getting it all back together? I was replacing the timing and drive belts, pulleys/tensioners, and waterpump.

I'm guessing the pistons mashed up against the valves? If the car isn't operating properly, should I assume I'll need a valve adjustment? Or should I look to make some sort of repairs BEFORE starting the car? I'm hoping I didn't cause any catastrophic damage, as I stopped once I started hitting abnormal/spongy resistance.

I suppose I knew just enough about what I was doing to cause some damage.

 

Folks,

Would he be able to assess any damage to the valves by removing the valve covers and, keeping the crank in time with the cams, looking for signs of damaged/bent valve stems and unexpected valve train resistance?

If The engine is properly timed before he does this, it should not lead to any additional damage, yes? Other than possibly exacerbating any existing damage?

For that matter, if everything is timed properly, a compression test should not cause any additional damage past what is there other than further bending anything that is already bent and that will already need to be replaced. What's the standard approach?

 

Line everything up, put on the belt. Turn it over by hand and see how it feels with the plugs out. If it turns a couple revolutions with no binding or noise, do a compression test. If it binds at all quit and tear it apart.

 

Thank you both for responding. So to clarify, assuming no binding when turning by hand (plugs out, timing chain on), put it back together. Then run a compression test--remove ignition and fuel injector fuses, hook up battery, screw in compression gauge, crank for a bit, mark reading. Then hope for normal readings (120-175psi) for each cylinder? And if any read low (zero, I'd assume), I'd be looking at 4 bent valves for the affected cylinder. In this case, it should still be able to run briefly, if I wanted to take it to a shop?

If there is any binding, that would also be a bent valve? In this case, absolutely no starting it--immediately proceed with taking off the head and pulling all valves to find what's causing binding?

 

Since you didn't have the belt connected to the cams, I don't see how the valves could have moved at all. I'd have done exactly what you did by rotating the crank back to the original spot and aligning the timing mark. Then, I'd install my timing chain and tensioners and do what Andy said and see if I could rotate the crank two full revolutions without much resistance. Of course you want to leave the spark plugs out while doing this. If it rotates okay, make sure your timing marks are lined up and install the spark plugs and wires and get in and crank the engine and see if it starts. If so, then you're good to button it up and go about your merry way. If not, then you need to start over and see what you did wrong. Did you have all of the timing marks properly aligned when you started? If so, then I THINK you'll be okay. Just keep in mind that I'm NOT a mechanic, like Andy. I've just been working on and maintaining my own cars for over 50 years.

 

At top dead center only two pistons are at the top. One is set to fire and the other is at overlap. The problem is the other four cylinders. They are in various stages of the four cycles of operation. One is on the intake stroke, one is on the compression stroke. The other two are somewhere on the power stroke, and the last one is on the exhaust stroke.
This is a crude explanation of how this works. The problem is some of the valves MAY be open enough to bend if the crank is turned and the cams are static.
This is why most of the valves get bent when the belt or chain breaks while driving.
Bent valves can break off creating catastrophic engine failure.

 

Just an update, I put the new timing belt on and removed the plugs. With a 19mm socket and 3/8" wrench, it's easy to turn for more than a full cam rotation--once the belt starts moving. It takes more force to start the crank turning at times, but once moving there's no real resistance until I stop turning. I'm assuming that with real binding, I'd hit some patches of roughness even after I've got the crank turning (and continuing to do so). I've checked at least a dozen full rotations of the cams just to get a feel for things and make sure the timing marks are all lining up (which they are!).

I'm going to put the rest back together and then check compression on all cylinders. If I'm missing anything, please chime in. I'm fairly new to this sort of engine maintenance--bicycle repair is more my thing.

I'm just not having a good day. I had a toilet tank rupture last night, and it flooded all 3 floors. Had to take the day off to clean. I can only hope that the divine-car-beings have seen this and will take pity on me.

 

The compression check will tell the tale. Sorry to hear about the house problems, I would much rather work on cars.

 

Any advice on getting the 19mm crank bolt out after previously using it to turn the belt clockwise? I put the plugs back in and attempted to loosen the bolt with ratchet, making the crank/cams go in reverse... Can I use my impact driver (bauer 1050 ft/lbs) and 19mm Lisle oversized socket that I originally used to break the bolt free from the pulley, or would the crank/cams jump into reverse in this scenario? My understanding is it shouldn't but I want to be darn sure.




I video tutorial I was using just said to remove with a 19mm socket... I checked several other videos and they all skipped showing the removal of the bolt (without pulley).

 

Put your socket on it and put a long cheater bar over the ratchet handle and give it a quick, hard yank. That SHOULD break it loose. If not, you can brace the cheater bar on the ground and making sure you have all of the plugs out and wires off, bump the starter. DO NOT HOLD IT DOWN AND CRANK IT . Just one quick bump. Of course, you still have to have the socket on the bolt and the ratchet attached.