Yet Another 3.0 Head Gasket Thread

[Russianblue]

the minor leak can't be reached but i'll get to that later.

in the meantime, there's this noise which is more worrisome. I can't figure out what it is but if I had to guess, i'd say it might be timing chain slop. sounds like it's hitting that little divider on the inside of the timing cover. it's possible that this was here BEFORE I did this head swap. i'm not 100% sure.

this video is after 75 miles on the highway and much more evident (louder) than it has been at any other time. it's BARELY (if at all) present with a cold engine. maybe a TINY TINY bit and I rarely (if ever) hear it when it's in gear or while driving (probably drowned out by the fan and everything else though.

https://youtu.be/P2rPZ3nxxmw

but if the chain is hitting the cover...that ain't good. Probably living on borrowed time, no?

[Effduration]

Hard to hear, a video from the engine bay might be better.

[80stech]

Sounds like it's happening only on quick decel? Have you tried pulling the serpentine belt to eliminate all the spinning stuff?
Maybe a rattling heat shield ??

[andrewwynn]

Did you put in a new tensioner? Or non-oem ?

[Russianblue]

it's absolutely happening on quick decel. it does NOT ever happen on Accel or of there is any load on the motor. sometimes you can BARELY hear something when idling after first startup but it soon goes away. it also happens when i turn the car off.

pulling the serp belt would be a good test for sure. that one is pretty easy.

i did NOT install a new tensioner. i used the kit tool to pre-load the timing old chain tensioner. if the spring in the tensioner is just weak, then that might explain why i'm hearing it at idle, first start and decel....when oil pressure is lowest.

heck, maybe i just try a new tensioner. that's a super easy install on the Xer with my big 32mm water pump wrench.

[andrewwynn]

Chain guide failure is almost always due to tensioner failure. Loose chain means slop. The pretension spring does almost nothing it's all up to oil pressure. The tensioner force from oil pressure is many times the force from the spring and once the tensioner wears the force can drop 50-70% and you won't know until you hear the rattle or the chain derails and bends all your valves

[Russianblue]

bent valves!?!? I keep these in my toolbox to remind me of that time with the M20 and $hit falling out under the car and leaving a trail of parts behind me as I pulled over.



but now that I have graduated to a timing CHAIN, how do these tensioners "wear" out? is there some kind of seal inside or something? to me it looked like a super simple metal on metal cylinder. What would cause it to not hold oil pressure to the extent that it loses 50% or more of its tensioning strength? Some type of wear obviously.

ok...to answer my own questions I am now in another damn BMW rabbit hole of research.

1. looks like the original tensioner (P/N 11311404438) has been superseded by 11317838675. Arguments abound but there is anecdotal evidence that on the original design the oil feed hole is too small relative to the oil discharge hole. Not sure I believe that BMW was that egregiously screwed up. Scroll down to F1004fun's post.

2. Neither of the part numbers above is listed for any X5 model on RealOEM.

3. the 8675 part is actually the S54 tensioner and is listed by FCP as an "upgrade" over the original part. Pelican Parts also tentatively lists it as an upgrade.

4. the original replacement is damn near impossible to find as a single piece.

5. the aftermarket parts are all on backorder.

6. appears as though you can order the Genuine cylinder, piston and spring and roll your own "Original" tensioner for a lot less than the single original part, which is available nowhere which, and seems like is basically NLA.

7. I find this entire topic interesting. It implies in a way (given that BMW went away from its original design) that it's possible, although not proven, that lots of us have been potentially living with super mild chain noise in various forms that maybe we shouldn't hear, but consider to be the norm. In my case it's a bit extreme but i'm going to start listening for it on my younger motor.

So you are left with only a few choices.

a. replace the spring in the existing tensioner
b. build your own original tensioner
c. upgrade to the Genuine S54 tensioner (if you can find it)
d. wait for the aftermarket parts to come off backorder

This sounds like a 'grab a couple of used ones at the junkyard and see if either makes any difference...then get the real thing later if it works' type of situation.

[oldskewel]

Interesting rabbit hole. But it looks like those guys are concerned with performance around 6k rpm on a race track, not just normal driving.

Before going deeper, I'd try to feel for this chain issue, not just hear it. I agree it sounds exactly how a loose chain would sound. But if it is that clear and repeatable, you should be able to put your hand on things to feel and confirm the location of vibrations.

You know exactly where everything is from having it all apart. And I bet by now you can have the fan and belts off in about 7 minutes if you need to remove them to inspect safely.

The other idea to keep in mind is the secondary chain that goes between the cams. It has its own little tensioner + guide. Since you initially forgot some other bolts up in that vicinity, is there a chance that a loose bolt was missed up top there as well?

[andrewwynn]

Timing chain tensioner works like a hydraulic litter/follower.

It's filled with oil under pressure to expand. As they age the gaps between the piston/cylinder get bigger and the same amount of oil pressure nets less force on the chain or the tiny paths oil takes gets blocked reducing the internal pressure. Same net result.

I've worked with a few people where it was obvious the chain was rattling because you could hear it in start similar to my M54 which has lifter tick every cold start while they are pumped up. I can actually tell how low my oil is by counting the seconds until lifter tick fades.

If the chain sound goes away after oil pressure builds it's almost certainly weak tensioner.

The knock off tensioners can not be trusted and I would replace tensioners on certain engines proactively. Eg on m62tu change before 120000 miles and every 50k after that.

The sound in the video definitely sounds like a loose chain and if were my engine I would park the car until my OEM tensioner with new crush washer arrived.

If the brand/age is unknown it should be changed anyhow. If the sound is something else at least you can have some peace of mind about the chain not self destruct

[Russianblue]

I ended up ordering the parts (cylinder, piston, spring, washer) to 'roll my own' Genuine BMW stock tensioner. It was cheaper that way. Like $60 vs the $220 S54 tensioner.

The tensioner on the car is definitely the original because this car has been mine since 2010 with 100k and before that, belonged to my dad who bought it new. I've got all the service records since its birth.

To OldSkewel's point, I actually (finally) ordered a mechanic's stethoscope which will be here today. That should help diagnose more accurately.

And he's right, I know this stuff like the back of my hand. If it weren't such a PITA to take out that damn radiator shroud and fan every time i need to get to the front of the motor. I think hate fitting the shroud more than I hate trying to get the fan nut started.

and that's a VERY fair question whether I left out any other major car parts or installed them upside down, backwards or what have you, lol! I am sure that the upper tensioner was fully installed but I suppose that could also be worn. But before i go down that path I'll try this easy fix with the lower tensioner and see where we stand.

on a positive note, the car hasn't run this well in years. The motor feels great. Still not quite as 'peppy' as the 98k mile Xer but i'd bet that's just an age thing. Most likely the tranny with the lifetime fluid still on the original!