YD25 timing chain slipped, chain is loose and tight..

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s1256

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Hi all,

Got a D22 cheap (£150), but it's timing chain had jumped. So it wouldn't start, and after more investigation I can see the timing marks seem to be way out. When rotating, you can see the chain become incredibly loose, and then tight again. It almost looks like it's had the timing chain replaced, maybe it was a cheap kit or something. But my questions for those YD25 masters/mehcanics:

1. How could it slip so bad?
2. Why would the chain be tight partially when rotating, and then loose. (See atttached video)
3. Is this likely to be an oil pump failure related issue, i.e. oil pump went, and so did the chain tensioner due to that.

I plan to take the head off and chain the bent valves, slap it together and use it for a run around. I guess I'll see how bad the damage is once the head is off. It'll probably cost around £400 in parts to repair it, so I hope it's worth it.

Thanks
 

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I notice from the video that some of the links in the chain aren't very flexible, watch the link in front of the yellow painted one right near the end. The tensioner looks like it's struggling to keep the chain tight. I don't know if it would improve when running with hot oil being pumped around it, there might be something wrong with the links and that may be the cause of the entire problem.
 
are you turning the engine the right way? kinda looks like its going backwards.
is it the early model or the later common rail one?

i'll have to check but they typically take something like 30-40 turns to line up the marks. note the little marks on the cam gears.
 
I notice from the video that some of the links in the chain aren't very flexible, watch the link in front of the yellow painted one right near the end. The tensioner looks like it's struggling to keep the chain tight. I don't know if it would improve when running with hot oil being pumped around it, there might be something wrong with the links and that may be the cause of the entire problem.

Yeah I see what you mean, I'm still not sure why this would make the tensioner come in and out of tension, or if its enough to make it do that. I'll go through and check the links and see how stiff it is, if it's rock solid welded, then I guess that could be the problem.
 
are you turning the engine the right way? kinda looks like its going backwards.
is it the early model or the later common rail one?

i'll have to check but they typically take something like 30-40 turns to line up the marks. note the little marks on the cam gears.

Not sure which way its rotating.

The marks on the chain and gears are miles off though, and if in theory the chain and cam are fixed and rotate together equally then they shouldn't be where they are now? (it's the YD25 Di, D22 2005).
 

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Yeah I see what you mean, I'm still not sure why this would make the tensioner come in and out of tension, or if its enough to make it do that. I'll go through and check the links and see how stiff it is, if it's rock solid welded, then I guess that could be the problem.
i think your tuning it backwards. which is why the tensioner is coming in out of tension.

they take quite a bit of turning to get all the marks to line up because your referencing to the chain instead of the the engine.
tho i did have it on mine where the chain was installed 180 degrees out. but you need to get all the other timing marks in the correct spot to check for that.

you will need to of course pull the bottom cover off so you can check the primary timing chain.
if you pull the chains off, don't forget to lock the scissor gear on the injection pump.
 
Hi all,

Got a D22 cheap (£150), but it's timing chain had jumped. So it wouldn't start, and after more investigation I can see the timing marks seem to be way out. When rotating, you can see the chain become incredibly loose, and then tight again. It almost looks like it's had the timing chain replaced, maybe it was a cheap kit or something. But my questions for those YD25 masters/mehcanics:

1. How could it slip so bad?
2. Why would the chain be tight partially when rotating, and then loose. (See atttached video)
3. Is this likely to be an oil pump failure related issue, i.e. oil pump went, and so did the chain tensioner due to that.

I plan to take the head off and chain the bent valves, slap it together and use it for a run around. I guess I'll see how bad the damage is once the head is off. It'll probably cost around £400 in parts to repair it, so I hope it's worth it.

Thanks
I think this is just the valve springs pushing over the top of the camshaft...nothing to do with the chain having any problems
 
I think this is just the valve springs pushing over the top of the camshaft...nothing to do with the chain having any problems
Do you know about the proper slack of the right side of the top chain (the part that is going downwards when operating)?




They look much tenser when newly installed on some YT videos and guides.
What's interesting the piston protrusion is minimal, suggesting that the chain is not stretched (link below)... but the slack does not seem ok either.
https://www.yd25.com.au/images/site_images/timingcchain_diagnostic/Diagnose_11Mar14.pdf
I got a bad metallic rattle noise and I wonder if that is the stretched chain banging against something, so needs replacing and should be sweet or is the slack normal and I need look further?
Thanks
 
Having a closer look the chain was hitting one of the bolts. Tomorrow I am taking the harmonic balancer and bottom cover. I read so much drama stories about taking it off and breaker bar. I took it off my R50 with battery operated rattle gun. Planning to do the same on R51. Wondering how loose is the bottom chain is. Car is 250kkm but looks like well serviced. I wonder if I am looking at the factory chain.
 
I agree with Tweekie (3rd post) it does take many many turns for marks to line up from an unknown starting point.

When replacing the chain, you lust need to line up all the dots on the cogs with the coloured links on the chain as per instructions, but if you try to line them up after turning the crank (and very important clockwise - not anti-clockwise), it will take many turns.

Same with the balancer.

You Tube is your friend.

Spoken words from someone who has done their own timing chain replacement. :)

And your video does make the chain look very loose. I would replaceit ASAP.
Cheers
 

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