Terrible rattling sound coming from my engine!

[Kingsly]

Hey all,

So it's been pretty chilly here lately, and I've noticed my car sounds a bit rough when started cold. She's fine once heated up.

So tonight I came home from about a 40 mile drive and noticed upon parking that there was a horrible rattle coming from my engine bay. To be honest I thought it was my neighbors absurdly huge diesel truck running next to me. I got out to inspect, thinking perhaps it was my bumper cover or something that had come undone and was rattling against the chassis... nope. Popped the hood, and low and behold my M42 had somehow spontaneously converted itself into a very loud diesel (why it couldn't have converted itself into, say, an S54 is beyond me... :rolleyes:)

Anyway, it's 1:30 am so investigating further is not an option, but what on earth should I be looking for? Recent work done has been mustang injectors, fogged airbox, and FDM. That's it. Car has never been overreved, $shifted, etc.  Bounced off the rev limiter once ages ago when I first got the car.  

In my entire history with her she's been smooth as butter. I don't notice any power loss, idle is smooth, etc. Just this horrible sound.

Help?

[twright]

Does it sound like an exhaust leak?  Start the engine and put your hand near, but not on, the exhaust side of the engine.
If you feel any warm air blowing, you have a leak.

[roundel318]

Can you record a sample for us to listen to?

[txleadfoot]

sounds like part of the timing system is malfunctioning.  Is the oil pressure good?  I'd check for timing guide bits in the oilpan and change the tensioner if you haven't had it changed already.  mine sounded like a diesel engine when the tensioner wasn't extending fully.

[derek9702]

I agree.  I heard the same noise you are describing when I cranked up my car one morning.  It was the guides for the timing chain.  Now I am in the process of rebuilding the engine.

[peerless]

Yep, its time to pull the front covers and address chain guides or simply rebuild the engine, which for a M42 is a good thing. Trust me they need all kinds of little upgrades to make the even better then before.

If you ignore the noise you will shatter the original stamped steel chain guide, if you haven't already. Pieces will rain down on the crank gear and will go between the gear and the chain slipping the chain. At that point you will loose your timing and you will bend at a minimum 8 valves. Then you can add a tow bill and valves to your rebuild costs.

Pictures Anybody? (I have lotsa lotsa more if you want)

[Kingsly]

Great. I'll try and record a sound sample. Basically it's like the VANOS rattle I had on my 325i but much louder.

How much am I looking at were I to have my mechanic do it? Alternatively, time it takes were I to do it?

How much am I risking by driving it about 100 miles before taking her to the mechanic (christmas and stuff... I NEED my car!)

[txleadfoot]

i'd say HUGE risk!

[Kingsly]

Well I talked to my bimmer specialist (it's hilarious when we talk, innocent bystanders can't understand what we're saying... it's all chassis codes, part numbers, and acronyms) and he recommended a new chain tensioner. It's been ordered, we'll swap it in later this afternoon.

Fingers crossed!

[derek9702]

To be cautious, I would check it out.....could be the difference between couple hundred dollars and a couple thousand

[Kingsly]

Check out the chain guides? Assuming the new tensioner makes the sound go away, I should be golden, right?

[peerless]

Check out the chain guides? Assuming the new tensioner makes the sound go away, I should be golden, right?

Well anything to keep the chain from getting all slap happy and busting up the guide rails. I think you are just delaying the inevitable though.

[Kingsly]

Okay problem solved. First off, car was with the mechanic a lot over the last month, and somehow they "lost" 4 quarts of oil that I had just recently put in. :mad:

I topped off the oil and took her to my BMW specialist, he replaced the chain tensioner (which was seized from oil starvation) and now she purrs like a kitten.

Last time I let someone I don't know touch my car...

[szed03]

I remember when mine sounded like a diesel until the oil temp came up...same thing, replaced the timing chain tensioner and no more noise ever since.

[Kingsly]

Yup, I'm glad it's all sorted. Of course I've just gone from one problem to another... :rolleyes:

A mercedes-benz is starting to look really good right now.