When should the timing chain be replaced?

[jgraves]

I have a 1991 318i with over 206,000 miles.  I had previously owned two 325i's and knew I had to replace the timing belt every 60,000 miles.  I am the second owner of this car and I doubt the previous owner ever changed the timing chain.  Most people I know have no idea about the M42 engine when it comes to the timing chain.  What is your expirence and when should I have it changed?

[Choking Hazard]

My car has 260k miles.  I just replaced the timing chain- mostly because I already had it.  Anyway, the old chain looked fine, and did not seem noisey, but when I put in the new one, it was substantially tighter.

Now, since the car won't start, probably due to the other mods I made at the same time, I can't tell you if it really helped, but I can tell you that by 200K miles, it probably needs replacing- which means I have another one coming up in a few thousand more miles.  Oh boy.  I sure as hell better have the white one going by then!

[RED IS 91]

100K but I have over 200K and suspect it's original on mine.

http://www.esatclear.ie/~bpurcell/318ismaintenance.html#timingchain

[DesktopDave]

271k on mine, but the PO had replaced a few components...I'd go for 150k or so.

[jgraves]

I appreciate all the advice.  There are so many people that have no clue when comes to the M42, I guess most of them think it has a self adjusting tensioner like on the E36  and newer six cylinder engines.

[Letsplayskatch]

Mine went on my first engine at 130k, which is about right when you factor in the 1/3 extended tolerance over the recommended replacement mileage. Now on my 3rd engine

[tom d]

i striped down a m42 at 180k miles. the chain was in pretty good order. the timing rails on the other hand, were trash! i wouldn't worry much about the chain. but, look closely at the rails.

tom

[race2win]

My car is pretty new to me but has 168K on it. I can hear some rattling/vibration noises at times, especially when the car is cold....most likely the chain and/or guides? Other than noise, is there any way to tell if the guides & chain are in need of replacement without completely pulling apart the front of the engine?

[RED IS 91]

I appreciate all the advice.  There are so many people that have no clue when comes to the M42, I guess most of them think it has a self adjusting tensioner like on the E36  and newer six cylinder engines.

The m42's  do have  a self adjusting tensioner.As the chain stretches  the tensioner extends further.

[jgraves]

Are there any particular things or signs I should look out for with the engine to let me know the timimg chain could be a potential problem?  I have never had any problems with this engine, but I want to avoid any possible problems with a long trip out of state.  I have known a few people that thought it was possibly their timing chain and it was actually the fuel pump stalling the engine.  I have never heard of anyone that had a timing chain break in an M42, but plenty of timing belts in the E30 325's.

[Choking Hazard]

There are a few posts on this board about chains breaking.  I recall reading about maximum extension of the tensioner....  if the tensioner showed more than 3/4 in extension or SOME OTHER VALUE.   I really don't recall the actual amount.  Probably search "tensioner"

[RED IS 91]

You should remove you oil pan and look for bolts ..............
http://m42club.com/forums/showthread.php?t=594&highlight=bolts+in+pan

while your in there look for pieces of chain or plastic from the chain guides.That will tell you if anything is going bad.Also take off your valve cover and look at the cam gear teeth. If they are pointy then it will soon be time to replace the gears and chain.
good luck

[race2win]

Hey everyone, so today I went through just about everything under the hood, looking for potential faults...including pulling the lower pan to check the bolts, as well as pulling the valve cover to take a look at the top of the timing chain. As I have mentioned earlier, I've only had the car about a month, & the previous owner only had it a year & never did anything with the timing chain and/or pan bolts.

Started by pulling the lower pan...great news as it all looks great in there. All the bolts were present & torqued properly, there was no timing chain/guide debris, & the lower pan had a fairly new gasket indicating someone was in there not long ago.

Then went to the top of the engine, the car has been running in-consistent lately...sometimes with an oscillating idle, sometimes sluggish performance. Started looking through some of the vacuum hoses under the intake manifold...pretty much ALL of them were cracked and/or damaged. I also notice the intake boot that goes from the MAF to the TB was actually cracked all the way through (can't believe it ran!). Picked up all but one of the pieces needed to replace everything, can wait to see how it runs once I get it all back together!

Lastly I pulled the valve cover to take a look at the top of the chain. Other than looking at the teeth, I am not sure there is any way to tell if the chain and/or guides need replacement from looking at it from the top, but here is a couple pictures of the cam gears & chain....




As you can see, the gears are definitely not pointed or apparently worn. In fact, to my un-trained eye, everything looks very good, almost like it has all been replaced at some point. It doesn't look like the gears have 168K on them to me, but I don't have another M42 around to compare with. What do you guys think? The upper guide looks great as well, the chain feels tight, & there was no debris in the pan. However, I obviously can't see the lower guides from up top, is it possible they are still hammered? Thanks in advance everyone!

[max123]

Replacing the chain sooner  rather than later is a good idea.  The chain rarely fails - it is a dual row timing chain and seems to be quite a robust design.  That said, I believe the chain does stretch and the cam gears can wear.  Speaking from personal experience, when I had the front timing case re-sealed I had my mechanic replace the chain as well.  First thing I notices was that I had more power and more torque throughout the rev band.  Secondly, I'm running a chip tuned for 91 octane and always had to run 94 octane or it would knock.  The engine now runs fine on 91.

I would say generally speaking that a new timing chain and cam gears will definitely liven up the old beast - it doesn't sound quite so angry at high revs and is much stronger and better behaved over all.

[sheepdog]

There is a VERY simple way to know.

Open the oil cap, and shine a light in and look at the sprockets,yes you can see them. You only need to see one. If the teeth are sharp, its done. The teeth should look like the picture above with slightly flat tops. Not spikes.

The tensioner matters, but if the teeth are worn it means your chain is stretched, changing your tensioner will do little. If the teeth are worn, the guides will be as well. The teeth wear because the chain no longer fits between the teeth properly due to stretch, this puts pressure on the front and back side of the teeth. If the tops of the gears are curled over at all, change it NOW.

On the e30, You should pull the pan every 60k probably and check that the upper, inner pan bolts and oil pickup bolts are tight. Use Locktite. On both e30 and e36, check the perimeter bolts, some may have fallen out. I don't recommend pulling it as it's a bitch. Just retorque everything properly with Locktite. If the torque specs are a dry torque (some will say add oil to the threads), use the proper number, the Locktite and any oil will make the bolt tighten more than it should already. If it is a lubed torque number, add 5-10%.