Engine rattles on startup

So far, it hasn't done it again for me. When it did do it, it sounded like it was mid engine on the passenger side. It sounded a lot like a rod knock.

Hmm, mine does it consistently on cold starts, lessened or eliminated after cranking with no FP fuse. Does not make the noise while cranking. Also, mine is quicker than a rod knock, multiple clatter noises for just a brief moment.
 
Hmm, mine does it consistently on cold starts, lessened or eliminated after cranking with no FP fuse. Does not make the noise while cranking. Also, mine is quicker than a rod knock, multiple clatter noises for just a brief moment.

Sounds kinda like BBs in a tin can? Mine isn't consistent, but otherwise...

Incidentally I put half a bottle of Lucas oil treatment in mine to see if it would quiet the noise down some, no effect. I don't like using it because it thickens the oil and reduces mileage (that's what I've seen when using it in the past, I know they claim otherwise) but it does stick to the parts better. So, I wouldn't think it would be lifter rattle due to no oil since the Lucas should be cushioning it.

I've also looked at the cats, don't see any shield issues. I would also think that a broken catalyst block would rattle more often than just on a fully cold startup. Still need to check the balancer which may happen this week as it's warming up a bit AND I think I've got a day with nothing scheduled on it!
 
Yep, that's what I have, 2-3 seconds of clatter then it's gone, too fast to localize not that I really can anyway as sound is just a wall to me. I am starting to wonder if it might not be a starter issue, like the solenoid isn't completely disengaging from the flywheel. It does have kind of a tinny quality to it. What do you think? I would also wonder if your weak battery might be an issue here, does a weak battery affect how strongly the solenoid draws back? It's been decades since I've had to deal with a bad starter, not sure if a weak battery might excaberate a weak solenoid issue.

You don't fit in with other BMW drivers? You must not be a prick then. :D

I think it's your starter. This was happening on a BMW of mine. I took the starter off and cleaned/lubed it because I figured it was not disengaging from the flywheel when I released the key. Never had a problem since.
 
Starter?

I think it's your starter. This was happening on a BMW of mine. I took the starter off and cleaned/lubed it because I figured it was not disengaging from the flywheel when I released the key. Never had a problem since.

Huh. I hope like hell that's it. Damn. I thought it was more from the front of the engine but it's totally possible...
 
I have this exact same issue, last week I took my belt off before starting it and the noise didn't happen, the next morning I had my wife start the car up while I watched the belt tensioner, sure enough, it bounced back and forth about 1/2 an inch and made a loud clanking noise for about 3 seconds then smoothed out. I think the spring is getting weak and it shows more in the cold weather, and once it flexes a few times it starts working better. I'm ordering a new one off of eBay, apparently they are the same part # as Ford Fusion tensioners, about $50 for Motorcraft. I'm also replacing all of my pulleys at the same time since they seemed to have a lot of resistance to spinning when I had the belt off....
 
Ive had lots of tensioner and belt issues with this car. When the tensioner does that, its failing and of you let it happen to long the belt will slip off and ruin itself.
 
Has anyone experienced said clank when driving at low speeds while letting off the gas?
 
Yes, it could be the tensioner. Also check and make sure you don't have a minor coolant leak onto the belt drive.

Yes, it has an auto-tensioner, but it most certainly can be replaced. I've replaced one of mine, and others on here have replaced theirs. You need a new "mechanic."

As always I knew you'd steer me in the right direction Joe. Thanks for clarifying this. I have argued and argued that this cannot be true. Thank you so much for confirming it. I didn't see any coolant leaks on the belt yesterday. Nor did I see any oil spuddered around the engine bay. I really need to finish detailing this car so I can put some pictures up for you guys. It's imaculate.

Is it expensive to replace the tensioners as well as the pulleys? Not that I'm not willing to shell out, but I just put down 560$ on the heated seat. (Ended up being a bad blower motor. Dealership asked for 718$ LOL)
 
As always I knew you'd steer me in the right direction Joe. Thanks for clarifying this. I have argued and argued that this cannot be true. Thank you so much for confirming it. I didn't see any coolant leaks on the belt yesterday. Nor did I see any oil spuddered around the engine bay. I really need to finish detailing this car so I can put some pictures up for you guys. It's imaculate.

Is it expensive to replace the tensioners as well as the pulleys? Not that I'm not willing to shell out, but I just put down 560$ on the heated seat. (Ended up being a bad blower motor. Dealership asked for 718$ LOL)

The heated seat was an easy DIY and could have been fixed for around $300.
It's just a tensioner and one idler pulley. Parts are less then $100. It's a pain to thread the belt back in, but it's not too hard to DIY.
 
Son of a...

I have this exact same issue, last week I took my belt off before starting it and the noise didn't happen, the next morning I had my wife start the car up while I watched the belt tensioner, sure enough, it bounced back and forth about 1/2 an inch and made a loud clanking noise for about 3 seconds then smoothed out. I think the spring is getting weak and it shows more in the cold weather, and once it flexes a few times it starts working better.

Damn, with prior cars have had plenty of tensioner failures (screamers, lock ups) but NEVER like this. This is by far the most plausible sounding theory. I'm going to pull the belt tonight after work and shuttling kids to water polo, soccer etc. This just sounds exactly correct. Fingers crossed...

Sometimes I just love LVC...
 
Damn, with prior cars have had plenty of tensioner failures (screamers, lock ups) but NEVER like this. This is by far the most plausible sounding theory. I'm going to pull the belt tonight after work and shuttling kids to water polo, soccer etc. This just sounds exactly correct. Fingers crossed...

Sometimes I just love LVC...

Before I changed career tracks and went into IT full-time, I was a mechanic first at Toyota and then at Ford. I've actually seen this happen a few times, especially when cold. I'm not 100% convinced it's the spring failing as it might be the bearing for the pulley locking up when it's freezing. I have a nice scar on my right middle finger from changing one out on a 2001-ish Celica, you had to remove the engine mount and jack the engine up just to get a tool over the bolt to take it off!

When I changed the pulleys and belt on my LS, I found it was easier to go in from the bottom after removing the plastic guard, I could get to everything and not worry about breaking the cooling system plastic, just my .02 if you're going to do it.
 
I was a mechanic...at Toyota and then at Ford. I've actually seen this happen a few times, especially when cold. I'm not 100% convinced it's the spring failing as it might be the bearing for the pulley locking up when it's freezing.

Well, I wish it were one or the other at this point. @#$%. I pulled the serp belt last night and it still has the startup rattle. Will try the starter thing next but it sounds very front of engine to me.

When I changed the pulleys and belt on my LS, I found it was easier to go in from the bottom after removing the plastic guard, I could get to everything and not worry about breaking the cooling system plastic, just my .02 if you're going to do it.

Nice tip. Will do next time. I went from the top and had my kid remove the belt tension using a crescent wrench on the lug of the tensioner. I used a long piece of rod with an allen wrench on the end to get the belt on and off the pullies. Not as hard as it sounds...
 
... I went from the top and had my kid remove the belt tension using a crescent wrench on the lug of the tensioner. ...

There is a square hole in the tensioner arm. A 3/8" or 1/2" (don't remember which off hand) socket wrench or pull handle fits in it. It makes it easy to hold the tensioner to relieve belt tension.
 
There is a square hole in the tensioner arm. A 3/8" or 1/2" (don't remember which off hand) socket wrench or pull handle fits in it. It makes it easy to hold the tensioner to relieve belt tension.

I bought one of these years ago.......

KD-3414.jpg
 
Well the bad news is that it isn't your tensioner, the good news is that you just eliminated quite a few possibilities, essentially everything connected to your accessory drive belt. So whats left?

  • Timing chain slop due to low initial oil pressure not extending the timing chain tensioners all the way
  • The fact that it only happens when it is cold means that it could possibly be oil viscocity related, I do know that fully synthetic oil tends not to "gelatinize" at colder temps like regular oil does and has generally better flow when cold.
  • Did you recently start using a different oil filter? Oil filters have check valves in them that keep them full of oil when the engine turns off, if this is not working properly, then the oil filter has to become full and pressurized before oil will flow to the rest of the engine, potentially adding a few seconds to the initial low oil pressure that is normal for all cars.

I'm sure there are more things, obviously there may be internal engine issues but I'm trying to stay positive :) Best of luck!
 
Well the bad news is that it isn't your tensioner, the good news is that you just eliminated quite a few possibilities, essentially everything connected to your accessory drive belt. So whats left?

  • Timing chain slop due to low initial oil pressure not extending the timing chain tensioners all the way
  • The fact that it only happens when it is cold means that it could possibly be oil viscocity related, I do know that fully synthetic oil tends not to "gelatinize" at colder temps like regular oil does and has generally better flow when cold.
  • Did you recently start using a different oil filter? Oil filters have check valves in them that keep them full of oil when the engine turns off, if this is not working properly, then the oil filter has to become full and pressurized before oil will flow to the rest of the engine, potentially adding a few seconds to the initial low oil pressure that is normal for all cars.

I'm sure there are more things, obviously there may be internal engine issues but I'm trying to stay positive :) Best of luck!

I've tried several different oil filters, only run Mobil 1 syn and have 5-20 in there now, tried a heavier viscosity but have not tried the 0-20. Will put it up on jack stands and have the kid start it to see if I can eliminate the starter theory. Right now still think I need to pull the front covers off and see if that shows me something obvious. Did the OP ever clear his issue?
 
No, not yet. Thought I was going to get it done, but then my daughter's car died hard. Right as I got that fixed (left headlights on, destroyed battery) it started raining. Had medical appointments today, have to take daughter for school books tomorrow. I've snuck a day off on Friday and didn't tell anyone about it, and it's supposed to be in the 60s and clear so I'm going to TRY to do something then. I swear my family works to ensure I can't work on the things I need to do. :(
 
Oh yeah...

No, not yet. Thought I was going to get it done, but then my daughter's car died hard. Right as I got that fixed (left headlights on, destroyed battery) it started raining. Had medical appointments today, have to take daughter for school books tomorrow. I've snuck a day off on Friday and didn't tell anyone about it, and it's supposed to be in the 60s and clear so I'm going to TRY to do something then. I swear my family works to ensure I can't work on the things I need to do. :(

I get that. I took kid 1 to water polo, kid 2 to dance picked up kid 1 then home for dinner. Then took kid 1 to do some batting practice (tryouts next week.) After all that I put the LS up on jack stands. Hoping it's your starter not disengaging theory. So got under there and listened from right below the starter, had the wife start it. Man, it really could be coming from the starter. Seemed louder than last night when I pulled the serp and listened at the front of the engine.
 
Beemer drivers

You don't fit in with other BMW drivers? You must not be a prick then. :D

Well, say what you will, but the fellas over at bimmernut.com are pretty supportive. Most of the guys there are into the older E32 and E34s so that might make a difference. Not to get off the rattle at startup issue, here's a thread I put up on a "old guy" site about rebuilding the engine and tranny in my 93 525.
http://www.network54.com/Forum/436002/thread/1350005505/last-1350970827/BMW+back+from+the+dead

/end hijack.
 
Well I caught my rattle today on video and I think it's different than what many are experiencing.

-I get this rattle on cold start-up occasionally, and when its cold out for a short time until its up to temp.

I'm leaning towards the belt tensioner or one of the pulleys.

*Turn up volume
Rattle - YouTube
 
Yes that's different from what I get. Yours sounds like lifter tap, as well as I can tell from the sound file over my crappy speakers.
 
Ya, honestly I just got back from Tenn, and I live in NY. I drove through both the blizzard on the way down and the blizzard on the way back.Delt with my girl friends family after 12 hour drive then drove 12 hours back.

For 260$ I sat on my fat butt. =D. The one part I should ask about, is the airbag system with the seat, from what I read on that awesome site you provided is that I could actually mess this up, (have it deploy on me or not function in the future) and I did not know how to disengage the feature ahead of time.

As for the parts, can you direct me? Also, the belt moves about 1/4 or a 1/2 of an inch on cold starts. Just like rallyus is stating.
 

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