Timing chain replacement went wrong

Hey guys,
Hoping you can give me some clarification.

So recently I did a chain replacement on my beater/project car. 2005 toyota yaris mk1 1.0 vvti 16v it has the 1sz fe engine.

Now I’m a fairly experienced DIY but I’m still learning. This was my first timing chain hense why I did it on my beater car.

When I started it up the engine cranked a few times and I heard a metal on metal noise.

Now the crank will only rotate 180° hense the pistons have hit the valves.

I understand I will have to take off the cylinder head and assess the damage and will have to do a valve replacement on the broken valves however before I do this I’m trying to figure out where I went wrong.

When I put the new chain on I made absolutely sure that cyl 1 was TDC compression stroke and that all the timing marks lined up. I made sure that the gold links on the new timing chain lined up with the marks on the cam and crankshaft sprockets as per the haynes manual and rotated the engine a few times and it was all smooth.

The only thing that I can think of that could have gone wrong was at one point the woodruff key fell out and allowed the crankshaft to be rotated independently of the cams.

Some people have suggested it is possible for the crankshaft to be a full revolution (360°) out of time from the camshafts. (It is a DOHC engine) My understanding was that the individual rotation of the crankshaft is irrelevant as long as its in time because the pistons and crankshaft will be in exactly the same position per rotation of the crankshaft anyway. As in they occupy the exact same space two times during a 4 stroke cycle.

I just want clarification that this is the case. Is it the case that the individual rotation of the crankshaft only matters on certain engines? Or is my thinking correct and I’ve most likely got my TDC wrong etc?

Any help would be appreciated

As you know the cam shaft rotates once for every two of the crank, so you may have gotten that wrong. In any event, it’s time to disassemble and figure things out. With luck you haven’t damaged pistons, connecting rods, or the crank itself, but it would be a shame if after replacing bent valves you discovered that you had. Recovering from this is beyond my experience, but you might consider replacing with a used, operating engine, they might not cost much.

What I’ve seen happen when timing belts/chains with hydraulic tensioners are installed, and if there’s any slack anywhere else in the belt/chain other than at the tensioner, the engine can be rotated by hand and the marks stay lined up.

But when you start the engine, and the oil pressure forces the hydraulic tensioner against the guide, any slack will be removed out of belt/chain. and the only way this can occur is by causing the cam shaft sprocket(s) to rotate slightly, which then causes the valve timing off.

And when that happens, bad things can occur.



This makes perfect sense and it must be what happened. There was definitely slack in the chain and when the oil pressure kicked in it must have moved everything slightly and caused this.
I will get the cylinder head off tomorrow and see how much damage has been done. Hopefully I can get away with just replacing the damaged valves

There should be no slack in the “pull” side of the chain and gears when checking the timing marks. The amount of slack on the tensioner side of the chain does not affect the cam/crank timing.

Before rotating the crankshaft with the chain off, the cams should be set 30 degrees from TDC so that no valves are fully open, otherwise valve damage may occur.

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Mind telling us what prompted you to replace the chain in the first place . . . ?

I’m curious

This is not something I would do on a 15yr old Yaris, unless I knew it was stretched, damaged in some way, the chain rails were worn, or something along those line

It was running like s**t. Lack of power, rough idle and a rattle from the engine. It had no fault codes so I did a comparison test and all was fine. There was no missfires so I assumed the timing must be messed up.

The when I dismantled it the old chain had a lot of slack in it and the tensioner was f****d, I could move it with my little finger, also the exhaust cam sprocket had slipped a tooth so I’m supprised it ran as well as it did.

thanks for the information :smiley:

Thanks for the information. I will remove the cylinder head and see which valves have been damaged and get them replaced.
I’ll make sure I put the chain on properly this time haha

I’m confused on several counts here. First as to why we are looking for any other answers for why this damage occurred beyond “The Woodruff key fell out of the nose of the crank”

Second…did the key actually fall out?

I’ve read over this post several times and it’s a bit unclear to me. Are you stating that the key it did indeed fall out? Or was that just a guess? Did you have to reinstall the key that you found on the ground? I mean you should well know if the key fell out or not…because you would have to reinstall it. So, I suppose I need clarification.

IF that key did fall out, then everything went south in that exact moment no need to look elsewhere. Again, I cannot tell if that statement was you taking a guess or not.

Yes the woodroof key fell out and I found it on the floor. So yes the crank was definitely rotated without the cams. At no point during this however did I feel any resistance when turning the crank and I only turned it by hand so I doubt any valve damage was done. After this I realised, aligned cyl 1 back to TDC and put the key back in so the crankshaft and cams were aligned again. The damage occurred when the engine was started not due to the woodruff key falling out. I know this because the engine rotated fine before I started it however after attempting to start it the crank will only rotate 180°

In my original post I didn’t make that very clear

Here is a simple question you might want to explore. Is this an interference or non-interference engine. If it is non, then the pistons would never hit the valves, and your problem is elsewhere.

Unfortunately it is definitely an interference engine :unamused:

I would find the manual for the car, to read the exact instructions for doing this job. Like the others, I would first concentrate on the correct way to deal with the hydraulic tensioner. I would be surprised if its action would change the timing so drastically, but it might. If the tensioner failed, or had a slow response, the chain might have jumped a tooth or more.
If I did the job, I would suspect a loose bolt or wrench left inside. Duh!

I have just had a thought, if I put the crankshaft position sensor plate on backwards could it mess up the variable valve timing and cause this? If the larger gap in the teeth on the sensor plate is supposed to be by the sensor when cyl 1 is TDC then I have put the plate on backwards…