Timing Chain W116/M117 - PeachParts Mercedes-Benz Forum

OldMercs · #1 02-25-2007, 08:05 PM

Just bought a non-running '73 450sel that I suspect will need a timing chain, seller claimed engine "just stopped" and the guides are broken. Provided everything else checks out ok how many related parts are routinely replaced in a proper timing chain job? Right now I have the chain and all guides on my list, is the tensioner or any sprockets and the oil pump chain recommended as well?

ctaylor738 · #2 02-25-2007, 09:10 PM

Well, if the engine "just stopped," it may be because the guide broke, jammed under the chain, caused the chain to jump on the sprocket thus altering the valve timing, causing the exhaust valves to hit the pistons, bending the valve stems, causing them not to close, causing a loss of compression, causing the engine to "just stop."

So you need to think about at least one rebuilt head.

In addition, you would want to do tensioner, chain, rails. cam oiler pieces, and injector seals. You should look closely at all of the sprockets to see if they are razor sharp or "egged." If so, they need to be replaced. Also inspect the cams and rockers for wear.

OldMercs · #3 02-26-2007, 12:11 AM

Well I suppose the first order of business should be to find out if the timing marks still line up then do a leak down or compression test to see if any valve damage occured (fingers crossed).

GaryF · #4 02-26-2007, 06:49 AM

I would suggest taking the two timing covers off, put a wrench on the crank and see if you can turn the engine by hand. If you can, do the cams still move with the crank. I presume you havnt tried to start it with the starter motor?!

OldMercs · #5 02-26-2007, 11:08 AM

No, haven't cranked it. I don't know how far the PO's mechanic got into it but the cam covers are loose, distributor cap is unclamped and the plugs are out. I'm thinking the mechanic was heading down the same path I'm going. From a shop's point of view, even if the chain didn't jump and the compression checked out I could definitely see this being sold as a timing chain/valve job as a typical "cover your ass" tactic. I can only imagine what the estimate must've been but since my labor is free that really is of no consequence. I'll dig into it tonight.

cth350 · #6 02-26-2007, 10:57 PM

where are you located? I know of a used, compatable motor that's just collecting dust and needs to be moved. It's on Long Island.

-CTH

OldMercs · #7 02-27-2007, 11:29 AM

Sorry, I'm on the other side of the country (L.A.), fortunately there's a steady stream of Merc engines in my favorite pick/pull yards should the need arise. Got home late today but managed to turn the engine over twice by hand (good) and found out that the timing marks still line up (nice). Oil is a quart low, how much of an oil deficiency does it take to cause the tensioner to back off and let a worn chain take out a guide? Battery couldn't be deader so today it charges so I can do a compression test after work. So far it's looking like I may have lucked out. Pushing my luck, how far if at all would any of you drive this car with a broken chain guide? I need to move the car to a location more suitable for repair work (as in not the street), it would be nice to drive it there. It seems that the tensioner may be the priciest part of this job ($100-$127), do these things wear out and are there specs to check them against?

Tomguy · #8 02-27-2007, 12:38 PM

Quote:

Originally Posted by OldMercs

Oil is a quart low, how much of an oil deficiency does it take to cause the tensioner to back off and let a worn chain take out a guide?

how far if at all would any of you drive this car with a broken chain guide?

It seems that the tensioner may be the priciest part of this job ($100-$127), do these things wear out and are there specs to check them against?

1) I'd say if you were 4 quarts low, that's where you might start to worry. These engines hold 8 quarts. 1 quart low is no biggie.
2) I wouldnt even start the engine or crank it with the starter if a guide is in fact broken. Push it into your driveway.
3) I have heard of the newer tensioners dying but not these older ones. Mine is 35 years old and still applies great pressure on the chain. Test it first

OldMercs · #9 02-28-2007, 10:47 AM

Started late last night so I only got as far as getting the crud covered steering pump out of my way so I could easily access the "bearing pins" holding in the broken tming chain guide. Service manual specifies a slide hammer for bearing pin removal, unless I pull the radiator it doesn't appear that there will be enough room for a reasonable "swing" with a slide hammer. Has anyone successfully removed the pins with a sort of puller? How difficult should the pins be to remove? Is there danger of pulling out the pin's threads before the pin itself? I can't wait to pressure wash this engine compartment.

Tomguy · #10 02-28-2007, 01:05 PM

I used the valve cover bolts in series with washers and large nuts (that the pin can pass through). As you tighten the bolt it will pull the pin out. Just BE CAREFUL to thread the bolt in far enough before you start trying to pull the pin. If not, you'll strip the threads.

ctaylor738 · #11 02-28-2007, 01:36 PM

There's also a neat tool for this. You can find it on ebay if you search for "mercedes pin puller."

If you go the home-made route, use a good quality bolt and a collection of hardened washers. The pins in the head can be quite stubborn and you may need to use some heat. Make sure that you have enough of the bolt in the pin to pull it, but don't bottom it out - that's another way to break it off. You may wish to have a #1 easy-out and the right-sized drill bit on hand.

cth350 · #12 02-28-2007, 03:33 PM

that pin puller makes a great stocking stuffer for the mercedes DIYer.
Not that xmas is coming any time soon.

If you can turn the motor by hand, do so for a few complete revolutions of the chain to make sure it's clear. A good flashlight should reveal all the guides (or what's left of them).

You can test the tensioner by making sure the pool of oil in front of it is full and then hand pressing the guide rail in front of it back and forth a few times. Each time it should become more difficult to move the rail and eventually it should be near impossible to get any substantial movement.

-CTH

OldMercs · #13 02-28-2007, 05:06 PM

The pin puller was exactly what I had in mind, since I can't afford to wait around for it I'll be making a similar item out of hardware store bits. The puller method has worked for me in the past on BMW steering bushings. Pulling the pins out with a threaded device seems to be more civilized than smashing my fingers. I will definitely try the tensioner test afterwards.

OldMercs · #14 03-02-2007, 12:06 PM

Good news, my home made pin puller worked like a charm. Bad news, though the marks line up the chain appears to be stretched beyond what the tensioner can compensate for and I'm pretty sure I've got bent valves. Got everything together having replaced the broken guide and figured either the car would run or not run so I skipped the compression test. The car eventually started, chain made a hell of a racket and engine ran horribly, pouring smoke out the back. The only way the engine would stay running was with the pedal either halfway or floored; so looks like I'm pulling off the heads. I figure the chain jumped, the PO's mechanic lined everything back up and checked for bent valves then gave the PO an insane estimate. I'm starting another thread re head interchangeability.