Is this S52 chain guide bad?

[cohny]

Two weeks ago I went to Mont Tremblant and wound up with a nasty rattling noise the morning I had to drive home for 7.5 hours. The car made it ok but if I went above 3k rpm the rattle would get pretty bad. Fast forward and the noise has now disappeared . I decided to go in and try and inspect the guides and rebuild my marginal vanos at the same time. Can anyone tell me if the play in this guide looks normal? This is with the tensioner removed. https://www.youtube.com/watch?v=AYorU1L-nBU

[Breeze1]

Two weeks ago I went to Mont Tremblant and wound up with a nasty rattling noise the morning I had to drive home for 7.5 hours. The car made it ok but if I went above 3k rpm the rattle would get pretty bad. Fast forward and the noise has now disappeared . I decided to go in and try and inspect the guides and rebuild my marginal vanos at the same time. Can anyone tell me if the play in this guide looks normal? This is with the tensioner removed. https://www.youtube.com/watch?v=AYorU1L-nBU

It might not look related to you, but you should check your oil level. The same thing happened to me once, the morning after climbing a mountain road. It turned out that I was low on oil (which I could not have known at the time because the previous owner had replaced a 6cyl dipstick with a 4cyl one, go figure ), which resulted in an insufficient lubrication of the tensioner, made worse by the slopes.

I was not as lucky as you were, since the lack of lubrication resulted in the overheating of one cylinder and the destruction of the spark thread (I was still able to have it repaired by a turner).

About the play in the guide, I'd rather let the pros answer you...

[bmwdirtracer]

While I doubt it's the reason for your rattle, no, I can't bring myself to call that amount of sideways slop normal The bottom of that rail should be a VERY tight fit on its dowel. How's that tensioner you removed?

[cohny]

Well that sucks... It's hard for me to say whether the tensioner is good or not. It doesn't seem bad. The piston puts up what seems like reasonable resistance in my hand and it doesn't seem clogged. I've attached a photo, but I'm not sure if it's much use. I am going to see if I can remove the cam sprockets and get a peek at the bottom where the guide is attached.

I managed to find a bunch of videos on youtube that sound a lot like what I was experiencing. Interestingly the noise seemed to go away when I got back from Canada so I was unable to get a video of my own.

https://www.youtube.com/watch?v=gSZz9L71Noo

https://www.youtube.com/watch?v=AD2rybG664U

https://www.youtube.com/watch?v=g4XEEPktSmc

https://www.youtube.com/watch?v=05rf6PDPHGI

The last one is particularly bad and my car only really sounded like that when I started it up to come home. The condition seemed to improve a little once I got going but I can't imagine whatever it is has just fixed itself.

[Breeze1]

The condition seemed to improve a little once I got going but I can't imagine whatever it is has just fixed itself.

As I said in my previous reply, what caused the rattling to appear in the first place is the fact that you drove it to Mont Tremblant, ie along steep slopes, probably because you're low on oil (think about the effect of gravity). When you left and drove back to a level road, the oil leveled as well, improving lubrication and getting rid of the noise along the way (what is enough for a level road is not enough for a mountain one); if you check your oil level you'll probably find out that it is below the minimum.

[cohny]

I hear what you're saying but I check the oil frequently throughout a weekend at the track. This weekend was no different and like always the oil never dipped below the top mark on the dipstick. My S52 burns no oil.

[Breeze1]

I hear what you're saying but I check the oil frequently throughout a weekend at the track. This weekend was no different and like always the oil never dipped below the top mark on the dipstick. My S52 burns no oil.

That's one thing out of the way then, but I couldn't help thinking there was a lubrication issue at some point, because I had the exact same issue under the exact same circumstances...anyway if it fixed itself that's all that matters

[bmwdirtracer]

Not really, especially since the car is used on track.

For a rattle as described, I'd suspect the chain tensioner, or the vanos.

[cohny]

Here's a better video. I am not looking forward to this replacement if that really is bad. I already ordered a tensioner.

https://www.youtube.com/watch?v=oOGvVrZA4yM