Author Topic: How to tell if timing chain needs to be replaced? (Read 10817 times)

juliea · « **on:** January 24, 2010, 02:28:58 PM »

Does anyone know how to tell if a timing chain needs to be replaced? I've seen various posts about looking at the sprockets to see if they are flat vs. pointy, but I've also heard that there may be ways to measure the "slack" in the chain.

Here's why I'm asking: I had one of my guides and my timing chain tensioner replaced recently. All other parts were determined to be serviceable. However, I then brought the car into my local BMW independent for another problem, and the mechanic said that the timing chain was making a lot of noise. He recommended replacing it.

The price tag was a bit higher than I was willing to spend, and I was confused since it seemed that all my parts were fine from the previous repair. I took off the front cover to see what things looked like. My sprockets look fine, timing chain tensioner looks engaged, and guides aren't broken. I'm wondering what could be causing this "noise". Any advice would be helpful!

juliea · « **Reply #1 on:** January 24, 2010, 03:02:33 PM »

Photos of sprockets and tensioner are posted here: http://picasaweb.google.com/juliea456/Cars#

DesktopDave · « **Reply #2 on:** January 24, 2010, 03:47:09 PM »

Looks fine to me. The noise can be hard to track down. I'd be tempted to look at the whole chain. There is a lower idler sprocket that could be noisy too. BTW, these motors are noisy to begin with. Has anything gotten worse since you've had the car?

Several board members have noted that swapping out the tensioner on an old stretched chain can quickly wear it out. That's hypothetical...your cam sprockets look much nicer than mine, FWIW.

juliea · « **Reply #3 on:** January 24, 2010, 04:54:27 PM »

Thanks DesktopDave - We're planning on taking off the lower cover this week and checking out the rest. I'm expecting that things will be similar, but like you said, worth checking. Since we're going through the effort of taking off the lower cover, is there anything else that you would recommend replacing while we're in there? The car has recently had all new coolant hoses, t-stat, waterpump, coolant flush, new oil, new crankshaft seal, new lower oil pan gasket.

-Julie

DesktopDave · « **Reply #4 on:** January 24, 2010, 05:11:54 PM »

You've already replaced all the things I'd do. Be sure you have a big breaker bar and stout socket for the crank bolt. Specified torque is something like 230 lb-ft. Also take care with the water pump (it shouldn't be much trouble since it's new), those ears are easy to snap off.

If everything checks out, button it back up then run the motor without belts to see if you have a noisy alternator bearing or PS pump instead of timing chain issues.

I see you replaced the lower pan gasket, did you find loose bolts or chain plates? I've never checked one myself, but I'd figure an oil pump might be noisy too.

92BMW318is · « **Reply #5 on:** January 24, 2010, 05:55:38 PM »

buy a new alternator belt

92BMW318is · « **Reply #6 on:** January 24, 2010, 05:57:27 PM »

http://www.youtube.com/watch?v=Kqay5rQJCf4
if this is the same noise then its the belt on the alternator
mine was loose and was making a loud screeching noise

juliea · « **Reply #7 on:** January 25, 2010, 11:26:41 AM »

Alternator belt was replaced back in April, and it's not a screechy sound, so I don't think that's it. Thanks for the advice though.

Oil pan was clean, too.

I'm thinking the cam timing might be off. We've had problems passing emissions and a little bit of a lumpy idle, and have ruled out almost everything else. Maybe this is causing some of the noise too. Good to know that the chain components look fine, though.

Thanks again for the help!

RED IS 91 · « **Reply #8 on:** January 25, 2010, 05:16:51 PM »

I did notice that the bolts that hold on your cam gears are off way to the side indicating that the timing maybe off . I believe that the bolt should be towards the center of the gear and not off to the side as is shown in your photo. At least every photo I've seen of cam gears show them towards the middle.
If Peerless(member) is around he would know for sure as he knows these engines forwards and backwards. Whether he responds ,I don't know.
good luck

colin86325 · « **Reply #9 on:** January 25, 2010, 06:36:32 PM »

Yes, the gears should have the bolts centered in the slots.

Choking Hazard · « **Reply #10 on:** January 26, 2010, 08:25:45 PM »

Wow. I'm typing with greasy fingers having just come in to look for info on timing chain replacement.
I toasted the head on my white car, and it a fit of "while I'm in there", ordered up a T-chain from pelican parts.
I've got everything off except the head itself and the freakin crank hub bolt. I am trying to convince myself it is not necessary now that I broke a drill bit in the flywheel timing hole when my makeshift hub brace failed during the attempted removal of the sob and I forgot about the bit.

I got comments
I got questions.
I got trouble right here in river city.

Comment:
My cams are also centered in the adjusting slots.

Question 1:
Where did the end of that drill bit go? (I'm sure I don't really want to know because I kinda think it will chew up the rear crank seal...)

Question 2:
I surfed around and found this:
http://www.bimmerwerkz.com/forum/attachments/3-series-e36/27017d1221128432-m40-motor-timing-info-crank.jpg
Now that I have the correct tool for the tdc hole below the starter, I don't feel any remaining drill bit piece when I put it in, but the crank will rotate about 3 or 4 degrees before it stops against the tdc pin. Could I have it in the wrong place? The cams being aligned for cyl no. 1 line up with the arrows being up, but that crank mark is about 5 more degrees counterclockwise from the alignment shown in the link, even when rotated to the end of the free play.

My cam gears have nice flat tops and the cdhain "looks" good, but what do i know? I already broke a piece of drill bit into the bellhousing, duh.

Anybody gonna share what they know 'bout the mess I'm in?

DesktopDave · « **Reply #11 on:** January 26, 2010, 09:05:49 PM »

I feel for you, but I haven't been there yet myself.

Two schools of thought on broken drill bits in bell housings...just run it until the thing blows up...or do it right & pull that sucker out.

I'd guess that there is enough space in the bell housing for all sorts of stuff...but I'm just guessing.

LOL...With a capital "P" and that rhymes with "T" and that stands for trouble. We did that one in High School. Robert Preston, Shirley Jones, Ron Howard, Buddy Hackett...what a film.

Choking Hazard · « **Reply #12 on:** January 26, 2010, 10:31:18 PM »

OKAY!

Thats two of us that say "try not to think about it!"

So I dug on in. New question: Whut the hayull kinda bolts is that head held on with? I thought it was a 10 mm. Going around for the first "pop" of torque release, but the last one (of course) wont get a grip with the socket. So I look a little and see that the head bolts are star shaped, with flats at the spots a regular bolt has points and a concave curve between those flats. edit-ok, it is a torx nut for a torx sucket. I have only seen bolts that took a torx bit.

So I got the cams and lifter boxes out- I wired the gears to the chain so they can't slip and clearly marked the cams. There is some increased probability I will put back close to right...

I really wanted to see the head damage but now I've gotta go tool shopping tomorrow instead...

Oh well, my rule is "can't have too many tools!"

Choking Hazard · « **Reply #13 on:** January 26, 2010, 11:57:53 PM »

Juliea-
I've been looking at this amazing build thread as guidance:
http://www.r3vlimited.com/board/showthread.php?t=159148
and this one:
http:
//www.m42club.com/forums/showthread.php?p=74529

I have read somewhere that the chain should never need replacing. Of course I have also read, when performing a timing chain replacement, you must also change the crank sprocket. Egad, I can't even get the freakin hub bolt off. I think you almost have to have the tool to hold the crank. What viscocity oil do you use? Maybe the tensioner isn't pumping up enough(?)... It is a fairly common attempted mod to advance intake timing by up to 5 degrees. Maybe that is what happened.

juliea · « **Reply #14 on:** January 30, 2010, 09:19:52 PM »

For anyone else who ever has issues getting the crank bolt off (I wasn't hte only one, as it seems to be from this post and others) - here's what we did. Make sure your battery has a good charge - we tried several times with a battery that wasn't fully charged to no avail.

Get a breaker bar and attach it to the crank bolt with a 22 mm socket. We removed the airbox and the radiator. Put a 2x4 piece of wood on the driver's side of the engine compartment, underneath where the airbox was. With the tranny in neutral, crank the starter. This should spin the breaker bar until it hits the piece of wood. Turn the starter motor off after the bar contacts the wood - you don't want to overheat the motor by leaving it on too long without it spinning. The impulse from the bar contacting the wood should provide enough force to loosen the bolt. It may take a few times to get it to work. You want the bar to go through about 90 degrees of motion to get enough acceleration.

Hope this helps...