Well, since my motor is over 300,000 miles, and about 120k since the last (only) rebuild, AND with the few different threads I've seen recently about grenading engines, I got to thinking it might be time for a timing chain. A trusted local MB mechanic confirmed for me yesterday that he recommends replacing timing chains every 100,000 miles, which is about what I thought, so I'm due. Mark also confirmed that he uses the "chain exchange" method in the workshop manual to replace the chain through the top of the motor with only the cam cover removed.
He did say it's kind of tricky though, and that even a single link of out-of synch while you're exchanging the chain will result in valve damage.
So I think I'll make a "tool", in essence a couple of axles on a frame that will bolt to the top of the cam box, and allow me to fully "install" and tension the new chain looped together with the old one, and then just manually crank the engine over to draw the new chain in. This should keep everything in time.
It should save a lot of $ since the job runs about $500, and the chain and gaskets are less than $100 of that. (biggest pain is removal of AC compressor to get to the chain tensioner hydraulic unit which needs to be replaced with a manual tensioner for this job)
I'm planning this episode for about 5,000 miles from now, coincident with other engine service due. Once I get it all written up, I'll make the tools available on loan to anyone who needs to do the job. The goal is for the tools to make this an easy afternoon job. Should be doable.
I don't know if you need a special tool. I did my 500sec like that. I used to 2 needle nose vice grips. Simply place vice grips on same pulley (one jaw through hole and other jaw over chain), split chain between and add master link and new chain, turn engine, move vice grips to next holes, turn engine, move vice grips, etc. The needle nose need not be tight, just enough to hold chain secure on pulley. By keeping the old and new chain always on the same sprocket will ensure you don't miss a tooth.
Make sure you get a masterlink kind of chain link which does not require the special tool to flare the rivett ends unless you have access to such a tool. Im not sure on the 280 engine if there is a way to check chain stretch but on the diesels there is ( on the cames there is a TDC mark and by comparing this mark to the crackshaft TDC mark one can determine the stretch ) - one can allow up to 6 crankshaft degrees before one should replace chain. Its worth trying to measure the stretch to see if its really worth it.
Peter Merle
Good idea with the vise grips, flounder. Might just try that.
As far as gauging the stretch, I think a $40 timing chain every 100,000 miles is cheap insurance and I don't feel inclined to wait till the last minute of stretch limit before replacing it.
Plus, the more the chain stretches, the more the sprockets are subject to wear as the not-quite-fitting-anymore chain gets pulled into the sprockets.
The stretch gauging idea is a good one though if you're buying a truck and don't know how old the chain is, or if you want to keep an eye on it and record it, say at valve lash intervals. That is, in the interest of possibly changing the chain MORE often than every 100k.
And offset keys?!?!? I think it's easier to change the chain than to try and replace the keys in the cam or crank! Not to mention the fact they only address valve timing and not the cain/sprocket mismatch that develops with chain stretch.
So did you turn the engine by pulling on the tail of the timing chain coming off the exhaust sprocket? I'd think you'd have to. If you turned the engine using the crank pulley or something the old "can't push a rope" effect would mean the intake sprocket would get dragged along, but the exhaust sprocket would sit still while the chain balled up below it.
Are you able to turn the engine (plugs out of course) by dragging on that chain end coming off the exhaust sprocket??
How does the cam sprocket that's "downstream" of the crank get turned when you do it like you describe in the article? Maybe it's different on the V8, but the only place to break the chain on the M110 is between the two cam sprockets.
The trick is to keep the opening of the chains on the sprocket. I was surprised to find the 110 manual showing the "feed in" as the proper install. I just assumed they wanted you to rip it all apart. The manual shows someone just holding the chain but that requires a helper and seems a bit risky. It doesn't seem to have the room for vice grips like the V8 though, perhaps some hose pinchers would work http://www.auto-parts.shoppingguides...ncher-Set.html or maybe someone makes some right angle vice grips? The arrows show placement of vice grips. Turn crankshaft clockwise until chain wants to come off sprocket. Take the one off the left and move it to where the right one was previously and the one on the right and move to where left was previously, turn again and repeat until the new chain is all the way in. Does this make sense?
My feeble mind was stuck on the idea of one vise grip on each sprocket. Two on the same one never occurred to me.[B)]
Very nice. If not the hose pinchers I should be able to come up with something that'll work.
The only thing still in favor of my original idea is it maybe being a little less fiddly than having to do it, more or less link by link. Doing it by yourself, that would mean a LOT of up and down going from engine top, to underneath to turn the crank.....
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