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Old 11-17-2008, 12:17 AM
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Join Date: Apr 2004
Location: KY USA
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Timing Chain E-Clips Came Off...And I Survived!

Here's the story:

Here's the story. Changed the timing chain, tensioner, upper guides, oil tube fittings, rail, on a M116 85 380SL (double timing chain factory) at 94K. At approximately 105K, something (NOT the oil tube fittings popping off, more likely a blockage in the oil tube itself from a loose piece of RTV) the LH cam, cam bearings, and rockers had to be replaced, and that side oil tube was cleaned like a gun barrel and new fittings installed. Recently at 120K, I've heard "timing chain slap" occasionally when left overnight. I thought that maybe the tensioner was leaking down but it seems to be OK and may be near the limit of its travel. The cam sprockets seem to be awfully shiny and pointy. There are faint score/wear marks on the chain. I'm replacing everything (including the cam gears) and the LH head guides will be replaced with METAL guides, I'm not doing this again...but...while I was tearing things down, I discovered:

1. The lower LH chain guide was broken, fortunately, not the side pointing to the chain, because no doubt that would have run up and caused the timing chain to skip (and worse, of course)...

2. I am missing a piece of the guide (not large); I did find a very worn from bouncing around piece on top of the "return" of the chain in the LH head;

3. Incredibly, BOTH (both) E-clips from the chain link were missing. I assure you that I had installed these properly and i had even inspected that they were installed correctly with a jeweler's loupe. There was a tiny piece of plastic wedged in the groove where the E-clip was, which is pretty good evidence that some broken piece of the guide had knocked them off. The chain still held, though - I suppose that as long as it is kept under some tension, the other side of the link won't walk out and the locking plate won't pop off. But still, VERY unnerving. I had probably been driving around like this for some time.

Due to limitations of tools, facilities, and talent, I'm not going to be able to drop the oil pan and/or remove the front cover of the engine to get the piece (or pieces) out.

So, a question for anybody who has taken off a front cover from this engine:

Where is it likely that the broken piece of guide wound up? Is it bouncing around at the bottom of the timing cover on a gear or did it drop down to the oil pan (where, hopefully, it won't do any harm)?

NEEDLESS to say, a complete oil change will be done on this engine upon completion of this work.
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Old 11-17-2008, 01:53 AM
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Join Date: Oct 2004
Posts: 3,165
Quite often the broken pieces of rail end up in the pan and from there into the oil pickup screen. If you have lots of pieces they can block the pickup screen to the point of causing problems. It would be wise to watch you oil pressure closely for a while. If pieces are causing oil starvation it will show on the gauge before the motor lets go. If you're oil pressure is low, especially cold then the pan needs to come off to find and remove those pieces.
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