Timing Chain Time

[sixerguy]

I'm doing my research before doing the Timing Chain on my 1986 635csi USA spec. I haven't done this before and am looking for parts and procedure advice. I'm planning on replacing the guides, tensioner, spring, chain and sprocket as well as the timing cover gaskets. Is there anything else I should definitely replace while I'm in there? I've already just replaced the water pump, cap and rotor so not thinking about those, just the stuff that's under the timing chain covers.

Also, I'm not really understanding the reason to choose an endless vs. master link chain. Also, I'm leaning towards going all genuine BMW, but in case anything It seems like endless is preferred maybe? Is the procedure more difficult if using endless? Also, should I plan on needing any special tools to complete the job such as a special socket or wrench I might not have in my arsenal? Any advice welcome! Thanks in advance!

[RSheiman]

How many miles on the car?

[DesktopDave]

You might want to check the oil pump drive gear, drive chain & perhaps shim it while you're in there...

I think the reason for an endless chain is to avoid a master link installation. That's how it is on my bikes, anyhow. If they're similar, the clip-type master links are a weak pont, and the rivet-type masters are difficult to do properly while the engine is installed.

[sixerguy]

About 160k miles on the engine. No weird sounds or behavior, but it'll give me piece of mind to have done with it.

DesktopDave: I'll research doing the pump drive gear & drive chain. When you say "shim it", shim what?

I'm not planning on removing the engine, so it sounds like endless is the way to go, yes?

[1986series6]

So you have an M30 B34 engine. With no obvious noise or chatter I don't think @ 160K you need to worry about the chain.
Are you confusing the problems with the S38?

[neville1507]

Bought a 1988 BMW 635CSI. Refurbishing the car and cannot find the timingchain and oil pump chainreplacementschedule. The engine has 150,000 miles on it, starts, runs and drives perfectly with no noise etc from the engine. I was wondering if we need to change the timingchainand oil pump drive chain, cannot find any recommended schedule from BMW. It does not seem to have been done from the history of the car I have received. - so I guess leave well alone, also I plan on driving the car gently at all times really..

[1986series6]

As far as I know, there is no scheduled maintenance on the chains
on an M30 B34 or B35.
From old age and ware, the guides can get brittle and fail, but
no replacement schedule.

[sixerguy]

I still haven't gotten around to doing anything about the chain, tensioner, etc. However, I just turned the valves and noticed that plastic chain guide appears loose. I stuck my finger down the left side of the time chain cover and was able to slide forward and back. Is that normal behavior or is the guide supposed to be pretty much stationary?

[1986series6]

That left side get pressurized by the chain tensioner with oil pressure.

https://www.realoem.com/bmw/enUS/sho...diagId=11_3049

[sixerguy]

Just to confirm, I was talking about #9 on the diagram being movable.

[1986series6]

It looks like #9 would be moveable even though
it's not on the pressure side. If it was locked in
position the movement of the chain could quickly
wear that guide.

[sixerguy]

Ok, thanks! Yeah, what started my interest in overhauling the timing chain was that many years (but not that many miles) ago my former mechanic suggested it after the car was in for a valve tune. At the time I didn't really follow up with why they were suggesting it. I don't hear any rattling on cold start up and with the valve cover off the chain feels tight enough. I'm not really sure what other signs or diagnostics one can do to determine the timing chain system healther without removing the chain covers. I put an scope down the inside of the chain cover and to my eye everything looked clean, and unbroken/unworn. With the valve cover off I could wiggle the chain very slightly at its apex, but just like .5mm front to back. Since the chain is a tiny bit wider than the sproket this seems normal to me.

[a2058]

I thought the plastic chain guide is held by two locating metal through pins, secured on by c-clips. This is the side of the chain that is straight up and down and tight. The other side is the tensioner that pivots and moves by oil pressure and spring force and keeps the chain pushed inward with pressure. So I would think the plastic guide side should be stationary, at least based on the way it’s held in place…?

[1986series6]

After looking @ the part again it looks like I missed the second
mounting point on the guide. I stand corrected, it does seem
it would be stationary.