Xoutpost.com - TIMING CHAIN NIGHTMARE

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I hope you never see a baseball size debri like what was in my oil pan , not including what I found sitting just inside the lower timing cover. When I drained the oil it was the blackest oil I have ever seen because of all the guides that had been chewed into bits. The previous owners must of been wearing ear plugs when they drove the car , it must have sounded like a diesel.
" BimmerM3inGA" is the writing on the square end of the cams suppose to be up?

I think I know the answer to this but I need to be sure. If the nut that holds the shutter plate and the bolt that the nut goes on is loose , would the cam turn when the engine is running? I don't think it would but not sure.

Quote:

Originally Posted by BimmerM3inGA (Post 1043904)

It has to be exactly spot-on. The engine will run without damage if it's off a bit, but you'll have a rough idle and it will throw codes to activate the Check Engine light. So you'll have to open it back up and redo the timing.

If you follow the Beisan instructions to the letter and pay very close attention to the final cam timing, it will be correct. It's kind of hard to describe out of context, but there is a way to verify that the timing is correct prior to buttoning it up. With all the fixtures still in place, you rotate the intake cam counterclockwise manually to the fully retarded position and measure how much the rear cam locking block lifts off the head. Anything more than 1mm is too much. Again, it doesn't make much sense out of context, but it's pretty clear when you're actually looking at it. As long as you have that measurement within spec, you'll have no doubt that the timing is spot on. But of course, you want to rotate the engine by hand through several revolutions - just to make sure!

FWIW, unless you know for sure that the chain guides are broken you don't HAVE to do this job. What I plan to do on my 4.6is is to monitor them and only open up the engine if I see evidence of the guides failing. The Bank 1 valve cover gasket is leaking pretty badly, and it's also due for an oil change. So, my plan is to remove the lower oil pan when I change the oil. If there are bits of plastic in the pan, I'll know it needs new guides. I'll also visually inspect the guides when I change the valve and timing cover gaskets. And then I'll remove the oil pan every time I change the oil. If/when I start seeing pieces of the guides in the pan I'll replace them.

Recently I changed the chain tensioner to the longer revised tensioner. Original tensioner was weak. I have the pan gasket to pull the pan and see if there is anything scary in there. The reason I think I should bite the bullet and do the job is because of all the engine mods I have done and I am concerned about a vanos going bad. I get the pucker factor when I hit it down. I hadn't thought of removing the pan each oil change, that's a great plan.

I've read the Beisan instructions several times. They are very good but I'm not good at understanding instructions unless I am turning wrenches while reading.

Here is a link to some videos I found helpful in understanding Vanos maybe they could be useful for you also. The more you know about it ,the less intimidating it becomes.
https://www.youtube.com/user/EuroAut...ch?query=vanos

bcredliner: VANOS failure won't result in a meltdown. Just a lot of noise and a crappy idle. I'd be more concerned about a stretched and loose timing chain than the VANOS. I know what you mean about the instructions just being academic until you actually start turning wrenches. It's the same for me!

If you do decide to pull the trigger on the timing chains and guides, it would be wise to do the VANOS at the same time. Even if they don't need it. You have to take all that stuff apart anyway, so you might as well take care of that at the same time. The rebuild kit is kind of pricey, and the seals are not nearly as easy to replace as on the I6. But it's still a hell of a lot less work than having to come back and do it later…

JAX01X5:Yes, the markings on the square (rearmost) end of the cams face up with the crank at top dead center for cylinder #1. FYI, cylinders 1-4 are on the passenger side with 1 at the front and 4 at the back. 5-8 are on the driver side with 5 at the front.

The shutter plate ("timing wheel" in BMW-speak) is held on by that reverse-threaded nut. If the nut is loose, the cam position sensor won't know where the cam is, but the cam will still turn with the chains. That nut isn't what secures the cam to the sprocket.

When I bought my 740i, the racket from the engine was unreal. It sounded like a diesel with a screwdriver loose in the crankcase. It had the triple-whammy of totally disintegrated chain guides, stretched chains and the VANOS death rattle. And the car only had less than 150K miles. There was a handful of plastic debris in the oil pan. In hindsight, it was probably unwise for me to have driven it the 10 miles to my house after I bought it. I should have trailered it. But I took it easy on the drive and I guess I got lucky.

Quote:

Originally Posted by BimmerM3inGA (Post 1043964)

I am concerned my 150 shot of nitrous will cause a meltdown if anything even a vanos is not working properly. That was the reason to go in and then do the timing guides at the same time. Working backward, but yes, I am more concerned about the timing chain. I had a rough idle and thought it was a vanos problem.

Thanks, BimmerM3inGA. I new about the nut but the bolt is also very loose and I don't think the Bank#1 intake cam would turn without the bolt being tight. They were so loose that the nut and bolt where resting against the upper timing cover and the shutter plate was so loose it had been spinning against the CPS . I believe that this is the reason that the car did not run, aside from the timing chain guides. "loose bolt would cause the cam not to turn"." loose nut would cause improper signal from CPS". Do you all agree?

Yes, you are correct. If the center bolt in the camshaft was loose, then the sprocket will not spin the cam. If that's the case, there's a nearly 100% chance you've had piston-to-valve contact if the engine was running when it came loose, or if anyone tried to start the engine.

Before spending any time/money replacing the timing chains and guides, I would determine the condition of the intake valves in that bank. Then you have to make a judgment call on whether or not you want to fix it. If you just want to do it for the challenge and learning experience without regard to the overall value of the car relative to the cost of the repair, then go for it. Especially if you got the car really cheap and just want to experiment on it.

If it were me and I decided to go ahead with the repair, I would not yank the engine. That is a HUGE FREAKING JOB and there's no guarantee that the newer engine is any better than the one you already have. I would jump on eBay and find myself a new cylinder head. I haven't looked, but I'd be willing to bet it would less expensive than that replacement engine, and a hell of a lot less work to swap out. I'd find a complete head with valves and cams and call it a day. As long as the pistons don't have huge gouges, or god forbid, any holes in them, they'll be okay to leave in service if they're a little beaten up.

Or, if a complete head does cost more, I'd buy that other engine but just swap the parts I needed and not the entire thing.

Since you can't do a compression test without fixing the timing problems, your path of least resistance might be to pull that head and see what you're dealing with. Then, based on the condition of the inside of the head, decide how you want to proceed.

I am probably going to pull the head although I noticed that none of the cam lobes are compressing the lifters except for one and it is barely on the lifter which makes me think that the valves have not been tagged. I know that it is not absolute but it does make me feel better about it.

Maybe you got lucky and nothing happened. I certainly hope so!

You may know this already, but the head bolts are one-time use only. If you do pull the head, order a new set of head bolts.