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1990' 560SEL
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281 Posts
Discussion Starter #1
Today, I basically cleared the way to reach those rail pins. Covers have not been opened yet. Some questions:

1. Is it necessary to disconnect the two fuel lines above the
left cover for opening the left cover? How much fuel spill
I'd expecting if I do need to do so?

2. I'm guessing that removing the cam sprocket before
replacing rails is a must. The question is how to loose
the can sprocket bolt? Do I need something to hold the
sprocket from turning? If I do, what to use? Or can I use
an impact to do the job?

3. How to decide if cam sprockets need to be replaced also?

4. Why right side rockers need not to be removed? Any risk to
damage anything withou removing them?

Thanks for your input...
 

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1965 220S, 1999 Volvo V70 (wagon), 2006 Ford Crown Vic Police Interceptor, 72 350SL 4 Speed
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1,830 Posts
I just did mine. I did a writeup over at mercedesshop.

Chain Guides Replaced - ShopForum

1. Is it necessary to disconnect the two fuel lines above the left cover for opening the left cover? How much fuel spill I'd expecting if I do need to do so?

Yes, you must disconnect the fuel lines. Use a rag to collect the gas that comes out. Use the blue nitrite gloves.


2. I'm guessing that removing the cam sprocket before replacing rails is a must. The question is how to loose the can sprocket bolt? Do I need something to hold the sprocket from turning? If I do, what to use? Or can I use an impact to do the job?

You do have to remove the sprockets on each side, not at the same time though. I used small vice grips and use one on the opposite side as well just in case the chain slipps. Getting the cams back into time is not really a problem if the chain does slip.

Do NOT use an impact on it. The bolts will undo and I used my hand to hold the sprocket.

3. How to decide if cam sprockets need to be replaced also?

The tips of the sprockets need to be flat not pointed. If they are sharp and pointed, there is too much sprocket wear and they need to be replaced. There are two extra sprockets behind the front cover, an idler and the distributor drive sprockets.

4. Why right side rockers need not to be removed? Any risk to damage anything withou removing them?

You do not need to remove any cam followers, or rockers, at least I didn't.

Remove the spark plugs to make turning the engine over easier. Get someone to help you turn the engine over so you can reposition the vice grip clamps. Make sure no parts fall down into the engine or you will have a bigger job on your hands. Stuff rags down the holes. When you put the new link on, the really small c-clips can get lost. Buy a magnetized tool, used to retrieve dropped parts, and put it by the link. This saved me once.

Check out my pics. The offset was huge and I really don't know how the engine even ran, valves crashing into pistons. The guides were either missing or broken.

I'm putting it back together now. I put the distributor back in, the plugs and I replaced the low pressure PS hoses while I was in there. The A/C idler pulley was almost seized so I removed it and oiled it. I also checked the air pump pulley and it was fine.
 

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CH4S Admin , Outstanding Contributor
1985 500SEC, 1991 190E 2.6.
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42,216 Posts
Did you clean the chain tensioner, and install with new gasket?
To loosen the sprockets you need a 22 mm wrench. You can use a large adjustable wrench etc to hold the cam (but not on the lobes).
A 27 mm socket and long breaker bar might come in handy (important: only turn clockwise!). You can order a puller for the guide pins, or fashion your own with a similar threaded HD bolt and nuts to use as a slide hammer.
Our DIY thread has the whole proceedure.
A wet/dry vacuum is a nice thing to have as well.
 

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1990 560 SEL with Euro engine, 1998 SL500 Sport
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2,957 Posts
Wow... good job. Thaks for the info. I have been searching for this type comprehensive explaination on the guides with pics.

wbain said:
I just did mine. I did a writeup over at mervedesshop.

Chain Guides Replaced - ShopForum

1. Is it necessary to disconnect the two fuel lines above the left cover for opening the left cover? How much fuel spill I'd expecting if I do need to do so?

Yes, you must disconnect the fuel lines. Use a rag to collect the gas that comes out. Use the blue nitrite gloves.


2. I'm guessing that removing the cam sprocket before replacing rails is a must. The question is how to loose the can sprocket bolt? Do I need something to hold the sprocket from turning? If I do, what to use? Or can I use an impact to do the job?

You do have to remove the sprockets on each side, not at the same time though. I used small vice grips and use one on the opposite side as well just in case the chain slipps. Getting the cams back into time is not really a problem if the chain does slip.

Do NOT use an impact on it. The bolts will undo and I used my hand to hold the sprocket.

3. How to decide if cam sprockets need to be replaced also?

The tips of the sprockets need to be flat not pointed. If they are sharp and pointed, there is too much sprocket wear and they need to be replaced. There are two extra sprockets behind the front cover, an idler and the distributor drive sprockets.

4. Why right side rockers need not to be removed? Any risk to damage anything withou removing them?

You do not need to remove any cam followers, or rockers, at least I didn't.

Remove the spark plugs to make turning the engine over easier. Get someone to help you turn the engine over so you can reposition the vice grip clamps. Make sure no parts fall down into the engine or you will have a bigger job on your hands. Stuff rags down the holes. When you put the new link on, the really small c-clips can get lost. Buy a magnetized tool, used to retrieve dropped parts, and put it by the link. This saved me once.

Check out my pics. The offset was huge and I really don't know how the engine even ran, valves crashing into pistons. The guides were either missing or broken.

I'm putting it back together now. I put the distributor back in, the plugs and I replaced the low pressure PS hoses while I was in there. The A/C idler pulley was almost seized so I removed it and oiled it. I also checked the air pump pulley and it was fine.
 

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1990' 560SEL
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281 Posts
Discussion Starter #5
wbain said:
I just did mine. I did a writeup over at mervedesshop.

Chain Guides Replaced - ShopForum
Very nice information! Thanks!

One more question: I do not have any vise-grip. I think I need three for the job. My question is what size of the vise-grip suit my job the best? 10" ones? Thanks.
 

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1965 220S, 1999 Volvo V70 (wagon), 2006 Ford Crown Vic Police Interceptor, 72 350SL 4 Speed
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1,830 Posts
allerton said:
Very nice information! Thanks!

One more question: I do not have any vise-grip. I think I need three for the job. My question is what size of the vise-grip suit my job the best? 10" ones? Thanks.
They are small with long jaws.
 

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1991 420sel
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267 Posts
Hi--There is a post of my chain/rail job on the DIY section as well (this was a post by snibble IIRC of a report I posted on the mercedeslist site). You will have to disconnect the 2 fuel lines. Loosen the gas tank cap to relieve gas tank pressure, and this will minimize fuel spill. Also remember to counter-hold the fittings at the fuel distributor or you may twist the metal fuel line. The best way to loosen the 22mm cam sprocket bolt is by immobilizing the sprocket with a large drift through one of the sprocket holes, braced against a wood block resting on the head. You could use a large pipe wrench on the camshaft (there are some handy casting sprues about half way down that you can grab onto), and sometimes it is necessary to use this method to line up the camshaft when replacing the sprocket. The reason why the manual recommends that the right side rockers be removed is that when you wind the new chain in (i) the cam will not try to "jump" as it is turned, and (ii) if timing is lost on the right side, you will be able to turn the crankshaft to retime without jamming the valves into the pistons. If you have access to a valve spring compressor, I would remove the right side rockers. But I understand that lots of chains have been replaced with the rockers in. This is a fun job but be sure you understand the procedure and be very careful that nothing falls into the engine. BTW, there is a fairly good booklet from Mercedssource.com on this job, and perhaps someone would lend it to you if you dont want to get it yourself. Recommended if you have not seen this job done before. Charlie
 

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1990' 560SEL
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281 Posts
Discussion Starter #8
I opened the right cover today. Please check my two pics. Do they show that my timing is off like 10 degrees? I have not opened the left cover yet.
 

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1991 420sel
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yes, it looks like the chain is stretched about 10 degrees. But note that even with a new chain, the cam marks may still be off by up to 5 degrees. They arent supposed to be perfect. But definetely change the chain while you are in there if it has been 100Kmi since last done. If it were me, I would use an MB chain, not an after-market one, as the MB chains are coming through with the fish-head clips, which are better and easier to use than the circlips. If you use a fish-head clip, be sure that the clip is installed so that the head points in the direction of chain travel. Charlie
 

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1990' 560SEL
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281 Posts
Discussion Starter #10 (Edited)
benzwag said:
yes, it looks like the chain is stretched about 10 degrees. But note that even with a new chain, the cam marks may still be off by up to 5 degrees. They arent supposed to be perfect. But definetely change the chain while you are in there if it has been 100Kmi since last done. If it were me, I would use an MB chain, not an after-market one, as the MB chains are coming through with the fish-head clips, which are better and easier to use than the circlips. If you use a fish-head clip, be sure that the clip is installed so that the head points in the direction of chain travel. Charlie
Thanks. Here is my chain which I got from a fellow member here. What's a "fish-head"? Do you mean a one piece clip rather than the two little circlips in the pic? Another question: is the timing considered retard 10 degrees or advanced 10 degrees?
 

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420 SEL, 1986 33K miles, 560 SL, 1987 173K miles
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allerton said:
I opened the right cover today. Please check my two pics. Do they show that my timing is off like 10 degrees? I have not opened the left cover yet.
Yes, those marks are off. One guy suggested the chain has stretched - perhaps - but this can also happen by slipping a cog on the sprockets if the chain tensioner has been taken loose. Valve spring pressure on the cam lobes likes to roll the marks out of position. I would look on the other cam to see if the marks match the first cam shown. Should slipping a cog on the crank happen - the sprocket which drives the electrical distributer can also go out of time. In that THAT unhappy event, you almost have to remove the timing cover which means either pulling the engine or some people drop the cross member and front end. Whichever is easier will depend on your shop equipment.

Keep in mind when lining all the marks up that the crank turns twice for every revolution of the cams, and eight times before the marks on the distributer sprocket will repeat. That little gem of hard earned information cost me more than two days work and it is not in the manuals.
 

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1990' 560SEL
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Discussion Starter #13
I replaced the rails today. The only hard part was to pull those pins. I made marks on each cam gears. I then removed left gear, did the job, put gear back and then the right side. When I tried to put the right gear back I found the timing mark moved clockwise like 5 degrees. Before installing the chain and gear, I used a vise-grip on the center of the right cam and tried to turn the cam counter clockwise to line the timing mark, but the cam would turn itself again clockwise and bounced back to the off-timing position. Could anyone tell me how to line the timing mark on the right cam? Do I need to turn it clockwise almost a whole turn to line them up or I can just pull it back counter clockwise? When do the ajusting, do I need put the gear and chain on or I leave the cam alone without the gear and chain? Why is the cam not willing to stay on the pre-set timing position? Is it because the tensioner was removed and it had not enough tension?
 

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1965 220S, 1999 Volvo V70 (wagon), 2006 Ford Crown Vic Police Interceptor, 72 350SL 4 Speed
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allerton said:
I replaced the rails today. The only hard part was to pull those pins. I made marks on each cam gears. I then removed left gear, did the job, put gear back and then the right side. When I tried to put the right gear back I found the timing mark moved clockwise like 5 degrees. Before installing the chain and gear, I used a vise-grip on the center of the right cam and tried to turn the cam counter clockwise to line the timing mark, but the cam would turn itself again clockwise and bounced back to the off-timing position.
allerton said:
Could anyone tell me how to line the timing mark on the right cam?
I ran into the same problem. I attached the sprocket and with the chain really slack, in my case, I was able to slip the chain over the sprocket to align it.

allerton said:
Do I need to turn it clockwise almost a whole turn to line them up or I can just pull it back counter clockwise?
You can just move the cam with sprocket attached. You will not be aboe to rotate the cam too much because the valves will bump into the pistons. No damage will occur though.

allerton said:
When do the ajusting, do I need put the gear and chain on or I leave the cam alone without the gear and chain?
You can also use a helper. You might have to remove the oiler tube as it might interfere.

allerton said:
Why is the cam not willing to stay on the pre-set timing position?
The cam is being moved by spring pressure on the cam followers.

allerton said:
Is it because the tensioner was removed and it had not enough tension?
Yes. Use that to your advantage. Also, check the cam timing marks for proper alignment. I advise a helper to move the engine while you adjust the chain and sprockets. Can you get your wife to help or your kids?

I did it, you can too.
 

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1990' 560SEL
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Discussion Starter #15
wbain said:
Yes. Use that to your advantage. Also, check the cam timing marks for proper alignment. I advise a helper to move the engine while you adjust the chain and sprockets. Can you get your wife to help or your kids?

I did it, you can too.
Thanks. Today, I asked my wife hold the cam back to the right position and I put the tensioner half on. Then the right cam just sit there without any timing off. I rotate the engine two turns, everybody seems fine. The crank tick mark is point 8 degrees. Hopefully it will come back to 0 after replacing the chain.
 

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1991 420sel
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Sorry--was away from my computer all weekend. The pix show a stretched chain and retarded valve timing. If you had slipped a tooth on the cam sprocket, the cam timing would be way off. (Divide the number of cam sprocket teeth into 720 to see how many crankshaft degrees one cam tooth represents.) It is often the case that a cam sprocket doesnt want to go back on because the springs have moved it slightly one way or the other. Just move it back a few degrees with a pipe wrench and have someone hold it there while you slip the sprocket back on. I take the right side rockers out to do a chain job, so this only happens to me on the left side. Do not try to rotate the cam even 10 degrees with the rockers in, as you risk jamming the valves agains the pistons. The chain you show is the aftermarket Iwis chain with the circlips. This is fine, so long as you do not lose one of the clips, and you have to put them on to wind in the new chain, and then take them off and put them back on to clip the new chain together. That is lots of manipulation with oily hands. Stuff rags into the engine openings and use a magnet next to the clip when installing/removing it so if it gets loose you dont lose it. The MB chain (at least last year) comes with a one-piece fish-head clip that is easier to use. The circlips work fine, they are just hard to use. Charlie
 

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1990' 560SEL
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Discussion Starter #17
Thanks to everybody. My job finally done. I just fired it, it sounded perfect. I'll change oil tomorrow.

BTW Charlie, my old chain was also made from IWIS. It looks like the original chain because it has neither fish clip nor circlip.

I did not change the tensioner because it is still strong. I could hardly compress the pin by my hands. I did install a new gasket there though.
 

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1991 420sel
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Yes--OE chain is Iwis, aftermarket chains should be Iwis, MB replacement chains are also Iwis, but with a different connecting link. If your tensioner is original at 183Kmi, I would plan on changing it soon. The spring isnt the problem, as that is just to get a little tension at start-up. The tensioner mainly works on oil pressure,and if the tensioner doesnt hold pressure, then it doesnt work hard enough and very bad things happen. If you can, get the MB one. The aftermarket ones reportedy dont work as well and dont last as long. Sometimes you see them on ebay at a good price. Congratulations on doing a fun and necessary M117 job!! Charlie
 

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1965 220S, 1999 Volvo V70 (wagon), 2006 Ford Crown Vic Police Interceptor, 72 350SL 4 Speed
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Mine was the original chain as well. I had to grind the links off. I'm not worried about the little circlips because they are there for location only and keep the link from coming off.
 

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1990' 560SEL
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Discussion Starter #20 (Edited)
wbain said:
Mine was the original chain as well. I had to grind the links off. I'm not worried about the little circlips because they are there for location only and keep the link from coming off.
I agree with you. No report on broken circlips. The only bad thing is that they are too small and easy to fall down from your fingers. I placed rag and magnetic thing down there in case...:D

BTW, I like your pictures, especially the one showing the home-made tool to drive the pin out.
 
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