Author Topic: Source of timing chain rattle discovered. (Read 4791 times)

tomstickland · « **on:** April 13, 2009, 06:50:32 PM »

110K and 4 years since I replaced the timing chain, sprockets and guides.
I noticed a rattle about a week ago. Finally got round to investigating the cause this weekend.

So the bolt that held the fixed guide at the top had worked loose and then spent a week wearing itself and the chain cover metal away. The top of the guide cracked off at some point and ended up half way round the chain route.

The engine ran fine for all of this and I managed a few hundred miles with a load of full throttle and high rpm too.

Has this happened to anyone else? Maybe I should have used a load of threadlock on the bolt?

I do have a heli coil suitable for the thread, but the mounting surface is all messed up, so suspect that I need the head off to have some machining done or replace the head.

The engine has done 230K and runs really well. I'm going to compression test it. It does stick a bit of smoke out on full throttle (not visible from in car), and I was told that this would most likely be the valve stem seals. So I could sort all of that out.
At 230K though, is it worth taking the bottom end out too and having the crank inspected?

Photos here:
http://www.flickr.com/photos/92961862@N00/sets/72157616680518280/

daveybmw · « **Reply #1 on:** April 14, 2009, 04:04:03 PM »

I'm in the middle of checking out the guides and chain etc. Put a puller on the bottom pulley and it is very difficult to move it off the crankshaft so that I can take off the lower cover. Is there any advice other than cranking harder on the pulley with the puller?

B318M42W · « **Reply #2 on:** April 14, 2009, 05:08:55 PM »

1. remove water pump pulley
2. undo the crankshaft bolt (don't be scared of the 230 lb-foot torque)
3. remove the Crank position sensor. (or at least back it up a bit...)
4. pull all the pully/vibration damper assembly. slides off real easy.

daveybmw · « **Reply #3 on:** April 14, 2009, 09:34:48 PM »

Thanks, I didn't realize that the crank bolt needed to be removed. I get to that tomorrow.

tomstickland · « **Reply #4 on:** April 15, 2009, 11:41:07 AM »

The crank bolt is usually very tight.
I've made up a special tool using 2 bits of angle iron with holes in the end. These bolt to the crank pulley bolt holes, making a sort of V shape sticking out onto the chassis leg. That gives you something to stop the crank turning whilst putting a big breaker bar on the end of it.

Jak318 · « **Reply #5 on:** April 15, 2009, 11:49:56 PM »

Did you recently to a timing job? It looks like you have the new style sprockets and guide rail. Did you notice the stud is broken off your sprocket? Check out the photo's of my setup.

B318M42W · « **Reply #6 on:** April 16, 2009, 09:43:23 AM »

funny... I did the timing job last month and one of the new sprockets also had a stud broken off... but I guess that the important one is the exhaust one since the sensor is right in front of it... ( but just to make sure, I swapped a good pin from the old sprocket to the new sprocket)

oh and did you know that there's a pin that you can use to lock the flywheel in place?? takes an 8mm shaft and the hole is under the starter (not directly under it, but the next "section" under it)

tim_s · « **Reply #7 on:** April 16, 2009, 10:24:51 AM »

good spot on the sprocket! tom i've got a spare newish sprocket if you're feeling anal and want to sort it, but important one is the exh side for the cam sensor pickup. can drop it by andy's sometime if you want? I take it you bought a new guide rail in the end, I've got one of those kicking about too!

tomstickland · « **Reply #8 on:** April 16, 2009, 06:46:53 PM »

Timing chain and sprockets were all changed 4 years, 100K ago.
Odd that that stuf seems to be broken off, unless it was never there in the first place.
I've never found half a stud anywhere.

I'm probably going to break the car for bits.

tim_s · « **Reply #9 on:** April 17, 2009, 10:06:53 AM »

yeah so i heard! quite a change from what you were saying t'other day? why the change of heart?

carl6405 · « **Reply #10 on:** April 19, 2009, 09:16:47 AM »

Not sure if you have removed it yet, but I removed mine and am in the middle of a oil pump replacement. The easy way to unscrew that big bolt is with a air impact wrench. Hit it a few times with the air impact wrench until it breaks loose, then use a regular wrench to get it the rest of the way out to prevent radiator damage. That bolt is torq'd to 200+ foot pounds. This method worked well for me. Hope this helps

kenika65 · « **Reply #11 on:** April 19, 2009, 08:36:13 PM »

Look at my how-to.

http://www.m42club.com/forums/showthread.php?t=6075