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450 - M117 Timing Chain Replacement

Started by WGB, 20 April 2007, 10:15 AM

lube

Interesting thanks Tim. Yes it's a one piece sump. I think the main problem is getting to the sump bolts, so I was thinking I could jack the engine up, undo the sump bolts, lower it again, remove the sump, then do all the rest.
No idea if this will work but I might give it a shot.

Cheers.

Gerard

I did this job  last Christmas on my 450, chain , top guides, cam sprockets and tensioner.

My method was slightly different in that I used cable ties instead of the vice grips.  Just buy a bag of 100 or 200, and using 2 cable ties to hold the chain to each sprocket, snipping one tie and adding a new one every 1/4 turn or so of the sprocket.

I turned the engine using the crankshaft nut and T-bar,  and extended socket.  I loosened the plugs (cant remember if I removed them altogether) but I didnt remove the valve lifters, so be careful when turning as the crank can "overshoot".

As a word of warning, my upper guides were very brown, and the end of one had broken off and was rattling around in there, with teeth marks on it from the sprocket :o.

Blessed there wasnt more damage.  I had meant to re-check the chain this winter, and purchase a set of offset woodruff keys to improve the timing, but alas, the car has been sold.

Gerard




TJ 450

Yikes, that has run through under the chain. Lucky there wasn't a catastrophe. :o

I've done the job on a few cars now, including MT's as mentioned. Once it is done properly, the peace of mind is very rewarding.

Tim
1976 450SEL 6.9 1432
1969 300SEL 6.3 1394
2003 ML500

lube

#33
Just thought I'd update with my progress...
I decided to do one side of the engine at a time, as follows:
Left side (with the engine in front of you) first:
Rotate engine so that master link (if present) is accessible on that side.
Mark cam + chain.
mark position of cam.
Plug gap with rag so nothing can fall down there.
Use cable ties to secure chain in tension, without obstructing access to guides.
Loosen nut on camshaft, putting wheel nut wrench handle through holes to stop cam turning.
Remove master link.
Remove cam gear (lightly tap off with hammer).
remove tensioner.
Remove tensioner rail (pin should slide out, don't worry you can't push it through!)
Remove tensioner rail.

That's where I'm at so far. Have a look at my pictures to see how I used the cable ties, and check out the state of my tensioner rail! At least the tensioner was doing it's job.



















I also used a magnet taped to a piece of tube to stop anything going anywhere near the hole just in case I fumbled!

Question: Does anyone think I should replace the slighty worn tensioner/banana rail, if so why? With the new plastic slider fitted it seems fine.

Also would anyone recommend replacing any bolts anywhere as good practice? Also what about the sprung washers on the cams?

Cheers.

WGB

Scarey what hides in these old motors and how long they actually hold together following decades of minimal maintenance.

If there is a spare unmarked rail easily accessible I would take it but I wouldn't foresee any problems using the old one with a new lining as the load is spread over a wide area.

Just be careful if you haven't removed the cam followers (fingers)   not to lose the correct camshaft to chain alignment and then try to turn the motor .

I think from memory I kept the engine with all the marks at TDC and then released the chain to change the sprockets and sliders.

The engine will safely turn with the chain jumped one sprocket but if there is a lot of carbon there may be some interference develop with a second sprocket tooth jump.

It looks like you replaced the chain first which is fine - the two jobs need to be treated as being almost separate items i.e. chain replacement vs replacement of cogs and sliders.

Thanks for the photos and hope it continues to go well.

Bill 

s class

Wow that tensioner rail is worn. 


[color=blue]'76 6.9 Euro[/color], [color=red]'78 6.9 AMG[/color], '80 280SE, [color=brown]'74 350SE[/color], [color=black]'82 500SEL euro full hydro, '83 500SEL euro full hydro [/color], '81 500SL

s class

Quote from: TJ 450 on 14 July 2011, 10:18 AM
AFAIK the 107 versions are different, in that they have a one piece cast sump assembly like the M100. The sump must be removed in order to remove the timing cover, as there is one oil pump mounting bolt that must be removed from underneath, as well as the oil pump chain.

On the 116, you can get away with just removing the pressed lower sump pan to access the bolt if I remember correctly.

Jacking up the engine should work, as I believe "s class" did this successfully with one of his M100s.

I concur with Bill, you might as well replace everything while you're in there (the oil pump should be fine though). It's a good opportunity to clean up the front of the engine and fix any oil leaks that may be present too.

Tim

Yes, I did remove the entire sump pan off one of my 6.9's with the enigne in situ.  But it was difficult.  I had to lig the enigne basically as high as I could with the engine crane, and remove the aircon compressor, brackets etc. 


[color=blue]'76 6.9 Euro[/color], [color=red]'78 6.9 AMG[/color], '80 280SE, [color=brown]'74 350SE[/color], [color=black]'82 500SEL euro full hydro, '83 500SEL euro full hydro [/color], '81 500SL

lube

#37
Thanks Guys,

I suppose I could fill the gap in the banana rail with JB weld two part epoxy and then smooth it off (seeing as it's ally I'd get a good bond), but I can't see that it's make any difference. If it ever gets that worn again then obviously the gap will cause more wear on the part in contact with the chain rollers.

It's not shown in the picture but I've marked the alignment of the cam relative to the engine and the chain relative to the cam sprocket, so I'm hoping that should be sufficient.

Once it's all back together I assume that a) checking the engine turns smoothly by hand, and  b) making sure the timing marks all line up at TDC will ensure that I haven't skipped any teeth?

In fact I'm going to do the chain last, so my order of work is: left side, right side, then chain.

Thanks for the info on the oil pan. When I'm all finished, before fitting the chain and putting the ancillaries back I may jack the thing up and take a look underneath, see if the lower guides are worth a shot.

Cheers.

lube

OK made some progress today, got the LHS all done no problem. Replaced all guide rails.

Unfortunately when undoing the chain master link on the RHS I forgot to undo the tensioner, and it seems that it pulled the chain around a couple of teeth. Now the two cams and the crank (obviously) are all still in the same position (marked on all) when the chain came off. I'm assuming the relative position of the central sprocket behind the water pump doesn't matter, therefore I was planning on simply pulling the chain around the LH cam gear in order to take up the slack, so in the end the master link will be two teeth clockwise from where it started (making sure the cams and the crank don't move).

Does this sound ok?

My other question is about the tensioner itself. People suggest filling this with oil prior to installation. I filled it (patiently!) through the small hole until there were no more air bubbles. Is this the right way to fill it?

Cheers.

WGB

#39
Yes - removing the tensioner is one of the earlier processes in the system and if the tension is removed from the chain it is not necessary to split the chain before working on removing sprockets and sliders.

The splitting of the chain can be left until the chain is actually replaced.

Another issue will be getting the correct timing when you have the new chain in place

If you have the timing marks all lined up there is a notch on the distributor body at which the rotor is supposed to point so that it is roughly correct for initial set up.

You will have to lift the edge of the internal plastic shield to see it as is shown in this picture.



Here is the notch on a 6.9 distributor which should be the same as a 117.

Bill

P.S - I have changed the pictorial and added a comment about removing the tensioner first.

lube

#40
Thanks Bill,

So you're saying I should have kept the chain together - that would have been easier! I know I should have removed the tensioner, I had just put it back on whilst rotating the engine to get the master link to the RHS. Oh well.

So in my current situation as long as the two cams are aligned with the crank I have nothing to worry about right? The distributor is off, I will re-align it when I put it back later. For now I just want to get the old chain done up and check that the engine is correctly aligned before I go for the chain replacement.

Thanks a lot for all your helpful advice.

Cheers,

Lube

WGB

I would put your master link back together again on your old chain - make sure the two cam and the crankshaft timing marks all line up with the tensioner blade and new liner in place but do not put the tensioner itself back yet.

Gently pull the engine through a complete cycle couple of times to make sure there is no interference (assuming your cam followers are in place) and then replace the chain - again pulling it through a couple of revolutions to make sure there is no interference.

At this point everything will appear to line up and then put the tensioner back in - filled with oil (May need some longer than normal starting bolts to pull it in and then replace with the standard bolts).
Usually the tension will change the chain position a little and what initially lined up will end up with 2 or three degrees of apparent chain stretch caused by wear in the cranshaft sprocket.

I would again pull the motor through a couple of revolutions with the chain tensioned and check you are happy and then put on the dissie and all the ancillaries.

Bill

lube

#42
Hi Guys,
Just another update, and  your opinions solicited please:
Got new chain on fine, as well as the tensioner on. The engine turns as smoothly as before, BUT...

As it is now, when the LHS cam is at the TDC mark the flywheel measures about 6-7 degrees past TDC. Before I started the job I measured about 8 degrees past TDC at the crank with the LHS cam marks aligned (I never looked at the RH cam marks). Now everything is back together and the tensioner installed the RH cam marks are not exactly aligned, but just over 1mm off (see pictures below). You can see I marked on the RH cam where the mark would be if I was one tooth off, and I think I'm ok. If anyone's interested 1 tooth would put you 4.3mm from the cam mark.

1 and a bit mm on the cams is around 3 degrees which means about 6 degrees at the crank, so this makes sense. It seems that the crank and the RH cam are aligned as thy should be, but that the LH cam is slightly retarded. Could it be that the new chain and tensioner is putting it under extra tension thus causing it to be slightly retarded?

I did also notice that there is much less slack in the chain between the two cams with the new chain installed.

Does this sound ok? 7 degrees off TDC with a new chain seems a lot to me. I suppose it must be wear in the crankshaft sprocket. Is it worth installing a woodruff key on the RH cam?

Thoughts? Below are the photos...

Edit: I just noticed that my current situation with new parts is almost identical to the photos at the top of this thread. Bill,did did the new parts cure the cam misalignment? Also, I should state that all my LH, RH references are looking from in front of the engine.

Cheers,

Lube

LH Cam: Marks aligned.


Crank: ~7 degrees off.


RH Cam: 1mm off.

lube

OK another update:
I removed the tensioner and lined up the RH cam mark and read about 3 degrees before TDC on the flywheel. I then pulled the LH cam back slightly so that it lined up with its mark, then did up the tensioner. Doing this caused the LH cam to be pulled back very slightly.
So I think it's just a case of the new tensioner slightly over tensioning the chain, causing the LH cam to pull back slightly from the LH cam mark. I'm sure after a few thousand miles it will be slightly looser and the marks will be in perfect alignment. I can't think of any other explanation as to why the cams should be misaligned with brand new sprockets and a brand new chain! Essentially this means there is about 1mm (or 5 degrees at the flywheel) of movement depending on the tension exerted by the tensioner and the amount of tension in the chain between the cams, meaning that it's probably best to get the alignment from the RH (opposite side to tensioner) cam marks.
Below are the photos I took of the final alignment.  I think it's slightly better than before. One thing I also noticed is that there is a hell of a lot more force on the tensioner rail with the new tensioner compared to the old one.
Hope this helps someone.
Cheers.

LH Cam in perfect alignment:


2 degrees off at the flywheel:


Slightly retarded at the RH cam:

WGB

Are you sure you have LH and RH correct - they should be as seen from the driver's seat.

Timing is taken from the RH cam and the crankshaft - LH cam mark never seems to line up exactly.

I would only test the timing after applying the tensioner pressure and after having pulled the motor through a couple of complete revolutions - as the chain needs  to seat itself on teh cogs correctly.

Bill