Author Topic: Is timing chain replaced? (Read 3977 times)

sfinsf · « **on:** February 11, 2012, 11:34:18 AM »

So I am looking for opinions and answers on my nagging question of whether or not my timing chain has been replaced. I realize that i could just drive the crap out of it and hope for the best, but that is just not how I operate. Here are some relevant facts based on what I have gleaned from a collection of forums:
-91' w/207k (M42B18), zero service records
-never replaced TC myself, 1st M42
-no excessive chain noise, some noise after purchase (Dec), new tensioner and running 20-50w has changed that.
-Both radiator hoses are new
-The entire shroud is in great shape and very clean

-Pulled lower oil pan, no metal fragments whatsoever, one very small piece of plastic from a guide
-the timing chain cover was cleaner then the surrounding block, there was plenty of gunk on the block, just none on the front cover or above.

-currently have the valve cover off, (had a wet plug) and before I button things back up, thought I would see if I could put this issue to rest. Need other pictures? More data?

What other signs are there? Can anyone shed any light on what other things i can/should look for? I am essentially attempting to determine if it's been replaced.

d.hitchcock · « **Reply #1 on:** February 11, 2012, 02:35:01 PM »

Those sprockets look pretty clean to me, and the profile gasket area looks very clean.

But it's awfully hard to say from the photos.

On my car (150k-mile 318is), the crank sprocket teeth were worn knife sharp.

On the cam sprockets, the wear was from the outer edges toward the middle, giving the teeth the shape of pyramids with the upper tips cut off.

My car's chain LOOKED like it was OK, but there's no way to be sure on an old one.

If your guides are broken, that there is reason enough to tear into the job, and if you have to remove the chain and sprockets anyway ... :-)

All it takes is the do-rey-mi. :-)

d.hitchcock

sfinsf · « **Reply #2 on:** February 11, 2012, 02:59:05 PM »

thanks for the input! The guides look like they are in really good shape, I could see the entire length of the tensioner side, all that I can see with a flashlight looks in really good shape. I measured my chain deflection this morning and with the tensioner in it's just under a 1/4"

DesktopDave · « **Reply #3 on:** February 11, 2012, 03:03:59 PM »

Certainly looks like it's been done. Those gears look nearly new.

I'd figure that the old tensioner rails were replaced...one little bit of plastic took a while longer to work it's way out. There are a few nooks & crannies in there.

sfinsf · « **Reply #4 on:** February 11, 2012, 03:24:14 PM »

dave, that's probably the best thing I've heard since the PO said "OK, I'll take that"! anything else that you can think of to check?

sfinsf · « **Reply #5 on:** February 11, 2012, 03:26:53 PM »

btw, is there an easy/nice way to get the VC bolt rubber seal off? and the new one on? I figure I could just cut the old ones off.

Nelson_40 · « **Reply #6 on:** February 11, 2012, 04:43:24 PM »

Just snip the old ones and press the new ones on by hand. Looks like you have a fine engine from the pics, enjoy it!

bmwman91 · « **Reply #7 on:** February 15, 2012, 06:22:30 PM »

Well, it certainly looks like the PO overhauled the timing case somewhat recently. Does the driver's side tensioner rail look like it is made completely out of black rubber/plastic, or is it steel sheet metal with rubber on it? If it is the latter, then it is the original rail. Do ou still have the old chain tensioner? If so, take a picture and we can tell if it was the original or an updated one.

My gut feeling is that you are fine given the condition of the sprockets. I get paranoid because I have had timing chain assembly issues a couple of times, but that was due to severe neglect on the part of the PO.

Did you also check the upper oil pan bolts when you had the lower pan off?

sfinsf · « **Reply #8 on:** February 16, 2012, 04:09:43 PM »

Thanks bmwman!
The old tensioner

from what I could see of the rail, it was the former, all black plastic
and yes, tightened the upper bolts while the lower was off.

bmwman91 · « **Reply #9 on:** February 17, 2012, 09:52:41 PM »

That is the old, original design, so it probably hasn't been replaced in the last 15 years. If you aren't finding pieces of chain, and the motor wasn't making horrendous noises when you bought it, then you might be OK. This really makes me wonder what was replaced though. Maybe an old guide rail pooped out & the PO replaced just that?