I know a 123 that was destroyed by a vac pump that disintegrated, they aren't immune from that problem but it was a run of the vac pumps on the 603's that were cost reduced or something and are responsible for a lot of dead engines :grim:
Don't wait until you hear knocking unless you like to tempt fate. They can fail before any noises start. Timing chain? If the engine runs strong you probably don't need one. I replaced mine at something like 260K just because the engine was being rebuilt. If your radiator isn't fairly new I would consider changing that as a plugged radiator can lead to a warped head. flushing one out is another alternative but they sometimes crack and leak.

Speaking of vacuum pumps, my "new" 617 vacuum pump just started making noise again (about 60K miles, 1.5 years). I thought it sounded like a loose valve, but it's the silly pump again. My indy is replacing it today. :rolleyes:

Man, your hard on vacuum pumps:D Better take a good look at the little "roller coaster" track on the timing device.

LOL, you are way ahead of me. I just got back from the shop and it turns out the vacuum pump is fine but the timing (IP advance) device is hosed, it has way too much axial movement (which is what I could hear clanking) and the cam is pretty scored up. With any luck my indy can get his hands on a new one (and a new thrust bushing) by tomorrow. If it get put back together, I need to drive it to chicago on sunday.

I think thats the first I have heard of a timing device going south. Wonder why. I had too pull one once and remember having a bugger of a time getting the timing chain off it and then back on. Your engine isn't ready for a chain yet is it.:) Good luck.

403,000+ miles!:D

It happened to me too. So it is not that uncommon.

Tom W

I agree with this. Never change anything you don't know is bad, mercedes parts are just way too expensive.

Tom W

Not sure, but he thinks it may be the thrust bushing behind it that got beat up when the first vacuum pump failed, when I saw it yesterday afternoon they were still trying to get all the down pins out the release the chain tensioner so they can slide it out. Now it has too much play front to back. The chain only has about 70K miles on it, so it's OK.

Ah, didn't notice that, I still hadn't heard of one going bad, now with Tom's story, thats two:)

I don't remember but I think the intermediate gears must be removed also, be interesting too see what those look like. That would be good if its only the thrust washer.

By "intermediate gears" are you talking about the chain sprocket (which does have to come out) or the drive gears for the IP (which come out the back, I think)? Anyway, since they are in this deep I'm having them replace the timing unit (including the sprocket) and the thrust bushing. They are not removing the IP, they just locked everything in place to (hopefully) not mess up the timing.

The "intermediate gears" (2) drive the oil pump and IP .there is allot going on behind that timing device and its all gota come out in the right order, I remember witting too this forum to figure it out :) I put the shaft that drives the oil pump in upside down.

eyeball it for now
 

I would check for stretch the eyeball method first and dig in deeper if not happy with those results. I followed the often mentioned procedure of lining up the camshaft and crank marks on mine at 220k, original chain and they lined up to Zero eyeball stretch, if I had more than 2 deg I would have gone into it per the FSM.

Just make sure to do it multiple times and average your readings, I did mine 5 times over each time showing zero so I'm not concerned. Eyeballing it should get you to within 2 degrees of precision. Since the tolerance limit is 4 degrees I'd recommend checking it with a dial indicator if eyeballing it gives you 2 degrees or more of stretch.

OK, I'm not messing with the IP drive now, the IP isn't even coming out, just the bushing on that shaft (from the front). On the 617 turbo, the oil pump drive is a chain, not a gear drive like the 616.

Edit: on the 617 turbo, it looks like this: