Timing Chain Slack not at TDC

[Scott7399]

Hi All,

I've done quite a bit of searching but I haven't found an answer yet.

I just bought a very clean 2007 Mazdaspeed 3 with 102k miles which also came with very thorough documentation and the VVT/timing chain has not been replaced. Currently, there is no rattle that sounds like a loose timing chain in other people's videos. There is a very short 0.2-second rattle but it doesn't seem to last as long or sound the same as VVT symptom sounds.

I've read that the timing chain slack that can be checked through the oil fill port should be checked at TDC(Top dead center). The chain is pretty tight at TDC (has <1mm of play if I try and pull up on it). However, there is an estimated 10mm of play at certain spots in the crank rotation. Is this normal? What is a normal or max amount of play to have in the timing chain when not at TDC?

Attached is a picture showing the degrees rotation from TDC and the mm of play. Below is the data I took to make the picture:

TDC 0º - 0mm of play
22.5º - 0mm of play
45º - 0mm
67.5º - 0mm
90º - 2mm
112.5º - 5mm
135º - 10mm
157.5º - 0mm
BDC 180º - 0mm
202º - 0mm
225º - 0mm
247.5º - 0mm
270º - 0mm
280º - 4mm
292.5º - 9mm
315º - 10mm
337.5º - 0mm
0º TDC - 0mm
I spun the crank around twice and the results were pretty much the same.

Thanks for your help!

 

[KiwiFlavor]

If the chain is taut at TDC, then you should be good. Just as another measure, take off your VC and see if there's any chain marks on it.

PS: This is the most detailed data I've seen someone took to measure their chain slack lol

 

[JohnnyTightlips]

I know with OEM motor mounts you will not hear it pronounced as well. If you get an RMM I have heard that can make the noise louder at start up. I would save for the job now as it is good to get done but it generally gets bad over time and does not just insta fail. You should be fine for a while just keep it in mind.

 

[Scott7399]

If the chain is taut at TDC, then you should be good. Just as another measure, take off your VC and see if there's any chain marks on it.

PS: This is the most detailed data I've seen someone took to measure their chain slack lol

That's a good idea, I thought about taking the timing cover off, but I think that would involve taking the crank pully off and at that point, I might as well do that VVT and chain. Thanks, I really wanted to make sense of why there was little to no slack when I test drove the car and why there was quite a bit the day after I bought it.

I know with OEM motor mounts you will not hear it pronounced as well. If you get an RMM I have heard that can make the noise louder at start up. I would save for the job now as it is good to get done but it generally gets bad over time and does not just insta fail. You should be fine for a while just keep it in mind.

Thanks Johnny, I was told that the car has new motor mounts, but I will check their condition.

 

[Mauro_Penguin]

Yes, that is normal or at least the slack on both ends of rotation is normal. It has to do with the VVT, but I don't remember if it was 8-10mm of slack.