Advice on timing chain...

[Armydiver]

I am replacing the radiator, fan clutch, fan, water pump, thermostat housing, all hoses, belts and so on.

Should I consider doing the timing chain as well since it will be accessible? Is that a difficult job?

While it is out of service I am going to ship off the valve cover to be refinished in wrinkle black with machined lines and emblem. Also going to tackle the SI board and odometer gears.

Love the car.....

[Son of a]

Do you have any reason to replace the chain or the tensioner? Doesn't sound like you do. I'm not sure that I'd bother. As far as an M30 is concerned, the anticipated lifespan of the chain is basically "lifetime." If you're tracking the car, severely modifying it, or just generally abusing it, then maybe its worth doing. It's a judgment call.

[Jeremy]

That's not a "while you're in there" type task. Not even close.

As Aaron said, the chains are pretty robust. Do you have any reason to suspect that it needs replacing?

[Martin in BellevueWA]

The problem with replacing the timing chain is getting a new chain without a master link. I don't trust the master link replacement chains as much as the original chain.

[George]

I say do it. Don't let these girly men shoot you down.


The chain isn't suspect so much as the tensioner/guide rail. It can be cracked and brittle and once that happens its only a matter of time before its in several pieces.

Is it a bitch of a job? I don't know as I've never done it with the motor in the car. With the motor out of the car its pretty straight forward with an impact gun and big torque wrench. The most difficult part is getting the lower timing cover off which requires removing the crank hub nut. You will also need a tool which keeps the crank from spinning while you tighten/loosen the nut.


That bitch is on there tight.

I say remove the timing cover, inspect the chain and replace the front crank seal and the timing cover seal and replace both the guide and tensioner.

At the very least, you'll never had oil leaks from the front of the car again.

[Mike W.]

The problem with replacing the timing chain is getting a new chain without a master link. I don't trust the master link replacement chains as much as the original chain.

The funny part is I agree. I have used master link timing chains before, without issue although not on BMWs, but to well over 6K, but I just don't trust them. Last M30 I did I ended up buying a second timing chain because the first did have a master link. I'll accept that it was my fault because I didn't check though, and I think I only paid six bucks or so.

Back to the OP, unless you have reason to suspect trouble, or are over at least 250K, I see no reason to bother.

[LA]

At least replace the guide and tensioner plastic wear pieces, check the spring length for the tensioner.

If you replace the chain, the sprockets should also be replaced because they wear together. If you have over 200K miles on the orig chain and sprokets, I recommend doing it - not 'just 'cause I'm there' but because it may be time...

Look and see if the chain still fits into the sproket, or are the sproket(s) teeth worn to a bigger radius?

Just one perspective

[Coldswede]

Well I did some rough calculations. thus;

If a car has 200k miles on it, and that car has 150k of those miles, cruising down the highway at 70MH at 2800rpm. Then the engine has revolved 356,000,000 times (Yeah that's millions) in those 150k miles!

Which means the cam chain has made the same number of revolutions ( I know, I know, the cam has "Only" turned 1/2 that)

I'd say that at least inspecting the chain would be in order.

Note to the purists: The above was figured with no calculator, rounded up for ease, and all figures were rounded approximations of reality. Regardless it's a lot of rotations.

[Son of a]

Just out of curiosity, anyone here have an M30 timing chain destruction story? Be specific and try to explain as much as possible about the use/abuse that the engine had received before and during the damage.

My guess is that there are not many of these stories out there. A timing chain is an extremely robust system, with the M30 setup being on the higher end of the spectrum. This is a totally different story than the S38/M88, do not confuse the two.

A few hundred million revolutions is nothing for something with a lifespan of perhaps a billion (semi-sane) revolutions.

[George]

Just out of curiosity, anyone here have an M30 timing chain destruction story? Be specific and try to explain as much as possible about the use/abuse that the engine had received before and during the damage.

My guess is that there are not many of these stories out there. A timing chain is an extremely robust system, with the M30 setup being on the higher end of the spectrum. This is a totally different story than the S38/M88, do not confuse the two.

A few hundred million revolutions is nothing for something with a lifespan of perhaps a billion (semi-sane) revolutions.

When I pulled my head and installed a new blue printed head for my turbo head the guide rail was in two pieces.

I routinely spin that motor to 7200 rpm (my current red line) now that I have the valve train to support that type of revs. There's no doubt I would have jumped a tooth if I just let it be.

Like I said, inspect the plastic pieces.

[craigb93]

As has been said the plastic guides are the weak link. If you have the thing apart now is the time. 20 year old plastic is now spaghetti.

Inspect the cam gear w/ the valve cover off. If the teeth are sharp pointed you need replacements as the cam will be retarded.

Put a master link chain on the bench and duplicate the staking like the rest of the links using a sharp punch in the center of the pins and rest easy, it won't come apart.

Dick

[Mike W.]

Just out of curiosity, anyone here have an M30 timing chain destruction story? Be specific and try to explain as much as possible about the use/abuse that the engine had received before and during the damage.

I have heard, but not seen of a M30 timing chain failure. I have seen broken timing chain guides, but no particular problems because of it. Now it is possible on a 7200 RPM engine things might be different, but I've also seen over 7K a couple of times on 250K components, as in an old Bav I used to have, and no issues there, not even valve float as far as I could tell.

[Son of a]

Just out of curiosity, anyone here have an M30 timing chain destruction story? Be specific and try to explain as much as possible about the use/abuse that the engine had received before and during the damage.

I have heard, but not seen of a M30 timing chain failure. I have seen broken timing chain guides, but no particular problems because of it. Now it is possible on a 7200 RPM engine things might be different, but I've also seen over 7K a couple of times on 250K components, as in an old Bav I used to have, and no issues there, not even valve float as far as I could tell.

That's my point. I too can think of maybe one time I heard of an M30 timing chain grenading. I wouldn't worry about the guides. Even if they are crumbling at this point, big deal. The chain and the sprockets will soldier on just fine. To the OP, are you going to turbo this engine, or otherwise thrash it north of 6k-7k on a regular basis? I doubt it.

[bmws forever]

My chain was still OK at 340k miles. OK meaning, I could not see noticable stretch when hung with the new one. The plastic guides were a mess, however. Both sprockets were not worn to pointed tips either.

[Mike W.]

My chain was still OK at 340k miles. OK meaning, I could not see noticable stretch when hung with the new one. The plastic guides were a mess, however. Both sprockets were not worn to pointed tips either.

Chains don't normally stretch, that's the misleading part. The rollers wear more than the links. I've put new chains on engines where they were actually longer than the old one, but were tighter.

[LA]

My chain was still OK at 340k miles. OK meaning, I could not see noticable stretch when hung with the new one. The plastic guides were a mess, however. Both sprockets were not worn to pointed tips either.

Chains don't normally stretch, that's the misleading part. The rollers wear more than the links. I've put new chains on engines where they were actually longer than the old one, but were tighter.

X2...Place a sprocket with 250,000 miles on it on top of a new one when you have a chance, and have a look.