Oh no.... Broken chain guide rail - PeachParts Mercedes-Benz Forum

450slcguy · #1 09-29-2009, 09:16 PM

1980 450SLC

Last weekend I started on replacing the chain guide rails. Figured it was time, just over 100k miles. Started on the drivers side upper outer. Came out nicely.

I then proceeded to the the inside rail. Got the pins out, and removed the rail. Unfortunatly, when I removed the rail it was broken in the typical place . After extensive peering into the head, I see nothing, no remnants or any sigh of the broken piece. I don't think it broke during the R&R, but who knows what happened.

It's been a couple of day's now, and I'm not sure how to proceed. I haven't put anything back together yet, I just stopped in my tracks. Where would the piece have gone? If this broke awhile ago it hasn't affected the cam timing or anything. What should I do?

Strife · #2 09-30-2009, 01:09 AM

Well...

Many have had this happen, and hoped that the piece(s) wound up somewhere in the oil pan, never thought about it again, and proceeded to drive. HOWEVER, there is one case (on this board, I think) where pieces were blocking the oil pickup and this was immediately obvious to the owner when he could not get good oil pressure at idle after changing the parts.

I had a guide break apart on my 380SL; In my case, I think the plastic piece broke, wedged itself in a spot where the chain basically wore it away to something smaller, and then some of it fell in. I had about a 1.5" x 3/4" piece I could not account for. 10K miles later, so far, so good. Thanks for reminding me

If ONLY removing the oil pan was not an extreme task for the home mechanic on this car. Basically, there are two choices:

1. Remove the subframe (actually, not terrible...if you have a lift)
2. Remove the engine/transmission (terrible, period).

It would have been very helpful if this engine had an inspection port, a two-piece, easily removable sump part,or something... I've fished around with a wire once or twice while changing the oil, but came up empty.

meltedpanda · #3 09-30-2009, 09:37 AM

Cant really help , but question??
How did you know the rails were bad?

donbryce · #4 09-30-2009, 08:23 PM

I'm not sure if your car has the same oil pan as mine, but as Strife noted, dropping the subframe is the only way to get it off and have a thorough look for broken pieces. This isn't nearly as scary as it sounds. Just follow the shop manual procedure. I fabricated a 1" box tubing engine support to allow removal of the subframe with the car on jackstands (I posted a thread with pics on this some years ago here). With the pan off, I found several pieces of the upper guides. Just to be sure I had 'em all, I crazy-glued the pieces together and accounted for everything. One piece had to be fished out of the left chain passageway, lodged in a block crevace. I'd hate to think if it came loose and got caught in the chain...

450slcguy · #5 09-30-2009, 08:25 PM

Quote:

Originally Posted by meltedpanda

How did you know the rails were bad?

I replaced the valve covers gaskets last year and saw the rails were a reddish/brown. I purchased the rails for preventive maintenance and finally got around to installing them. Car turned 100k miles about a year ago. Just goes to show how procrastination can bite ya. Ouch....