Author Topic: How to tell if timing chain needs to be replaced? (Read 10803 times)

juliea · « **Reply #15 on:** January 31, 2010, 05:56:49 PM »

Thanks for the help so far - I got the lower timing case cover off. Looks like the lower sprocket is pretty worn. Can you guys take a look at the photo posted here: http://picasaweb.google.com/juliea456/CarPhotos# and let me know if you agree that I should replace the lower right sprocket? If I'm going to replace that one, I'm guessing it makes sense to replace all four sprockets & get a new chain, right?

I've also been seeping oil. Based on the residue pattern, I'm guessing it's coming from my lower timing case cover gasket. I posted some photos of this too - could you guys also look at them and let me know what you think?

flyinglizard · « **Reply #16 on:** January 31, 2010, 06:57:43 PM »

If the head has been milled or the chain is stretched,the cam gear bolts will need to be off center. IMHO.
Some place in one of the books, it gives a max protrusion of the tensioner. The pics show it stuck out pretty far> almost to the second clip.
Yes, change the whole system complete.

MM

juliea · « **Reply #17 on:** February 01, 2010, 11:23:26 AM »

flyinglizard -
Thanks for the advice. I looked up the total parts cost for replacing chain, sprockets, and two guides that were broken - total comes to around $400 in parts! The three other sprockets come to $250 of that - what are your thoughts on whether I could get away with just replacing the chain & crankshaft sprocket?

flyinglizard · « **Reply #18 on:** February 01, 2010, 11:56:33 AM »

Try "Stu" at Imparts. I get most of my OE German stuff from him, for about 25 yrs. now.
The chains shows to be about 99$,tensioner about 68 or so, etc.
877 671 9998 , Rochester NY.

juliea · « **Reply #19 on:** February 01, 2010, 12:09:59 PM »

Thanks for the tip - I'll check it out. The tensioner is new - just purchased and installed - maybe 200 miles on it - do you still think I need to replace it?

DesktopDave · « **Reply #20 on:** February 01, 2010, 12:47:12 PM »

I'd leave the tensioner as is, no need to replace a new part. It'll adjust to the new parts. I don't think that your idler sprocket is that bad. I'm not 100% sure about that crank sprocket though. It's hard to tell. You'll be testing the chain for stretch too, right?

Did your mech change the right guide? It's the one on the driver's side of the motor. I might be seeing things, but are there a few cracks around that lower bolt hole? My usual determination of replacing or just cleaning is usually a direct relationship with the difficulty of taking it all apart again...

A stretched chain will be noisy even with all other components in serviceable shape. Might be that your old mechanic tweaked those cams to quiet the whole thing down instead of attempting to refurbish the whole timing case. These engines are pretty cheap used, my mechanic would likely have dome something similar unless I specifically told him otherwise.

juliea · « **Reply #21 on:** February 01, 2010, 12:56:32 PM »

The crank sprocket teeth are pretty pointy. We were thinking it should be replaced.

How can I test the chain for stretch? We were thinking of just replacing it, but it would be good to know if we can keep the old one...

I think the right guide was changed recently, but I'll take a closer look at the lower bolt hole. Thanks for noticing it.

I would like to avoid replacing the idler sprocket & the camshaft sprockets if possible - do you think these are serviceable?

DesktopDave · « **Reply #22 on:** February 01, 2010, 01:16:40 PM »

There's a spec somewhere about max allowable chain length. Every vehicle I've owned had a reference to it somewhere. I don't have it offhand, but IMHO it's definitely something to verify. If the chain is too long it'll wear everything else out much faster. I'd guess that the chain is OK because the tensioner isn't extended that much, but I take the time to check everything when I do auto work.

I didn't think the cam sprockets looked that bad, and I'm not 100% on the idler either. Just my $0.02...

juliea · « **Reply #23 on:** February 01, 2010, 01:33:47 PM »

Thanks - I'll see what I can dig up on the max. allowable chain length. Unfortunately, Pelican wants $150 for the idler sprocket, but if it needs to be replaced, I'd rather spend it now than have problems down the road....

DesktopDave · « **Reply #24 on:** February 01, 2010, 01:49:02 PM »

Yeah, they're overpriced at times. Great service though. I'll bet that other members of the board have great sources for parts.

Choking Hazard · « **Reply #25 on:** February 02, 2010, 09:00:18 AM »

I also use Tisher BMW (getbmwparts.com) for OEM parts, but Pelican is a class outfit and my preference.

Choking Hazard · « **Reply #26 on:** February 02, 2010, 09:21:18 AM »

I wasn't clever enough to think of the starter motor impact wrench approach. I ordered the tool to hold the crank, and it should be here today when I get home from work. When I get the lower cover off, I'll take some photos to compare with Juliea's pics. I guess I'lll add that wrench to the tool loaner zone when I am through, too.

KenC · « **Reply #27 on:** February 02, 2010, 02:14:48 PM »

Quote from: juliea;86409

The crank sprocket teeth are pretty pointy. We were thinking it should be replaced.

How can I test the chain for stretch? We were thinking of just replacing it, but it would be good to know if we can keep the old one...

I think the right guide was changed recently, but I'll take a closer look at the lower bolt hole. Thanks for noticing it.

I would like to avoid replacing the idler sprocket & the camshaft sprockets if possible - do you think these are serviceable?

FYI, the teeth on the crank sprocket are pointy brand new. I bought a new one thinking I needed to replace mine. I compared the new and old side by side for several minutes and found NO differences.

juliea · « **Reply #28 on:** February 04, 2010, 07:04:03 PM »

thanks for all the help so far. how about judging wear on the tensioner guide rail? mine has some scratches in the very top - does this mean that it is worn out & should be replaced?