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  #1  
Old 08-07-2004, 12:30 PM
Uk Merc Man's Avatar
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2.5 16v Timing Chain Nightmare!

please help....

armed with the info from this page: http://mb190.tripod.com/tech/timing.html I attempted to renew my timing chain and tensioner on my 2.5 16v today.

I removed the alternator and drive belt. i removed the old tensioner unit and the valve cover. i removed one link from left hand side of exhaust cam as viewed from the front, I connected the new chain to this and started to turn the engine clockwise via the crank nut, whilst holding the 2 pieces of chain tight.

this is where it went wrong.....

instead of gliding smoothly round, feeding the new chain in and keeping the cams in perfect unison, the chain slipped over the exhaust cam (the one on the left as viewed from the front) whist still turning the cam on the right of the engine (as viewed from the front)

what has now happened is I cant turn the engine over any more, I assume because the cams got turned at different rates/amounts I have something making contact somewhere internal???

It was turning over real easy ( i took the plugs out to help me) but now it feels as if I am up aganst something fairly hard, I dont want to try to run it any more in case I bend something.

so, what do I do? the new chain is approx 1/3rd of the way round, and I cant turn the engine over in its present state to either retrieve it or feed the rest iof the new chain in.

The only thing I can think of is to remove the cams to allow all the valves to close?

Any help greatly appreciated.

and to think I was planning on driving to work monday morning.....

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  #2  
Old 08-07-2004, 12:55 PM
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I'm not a pro, but couldn't you remove the rocker arms allowing the valves to close?

Are there timing marks on each cam you could use to line up the balancer with afterwards to get the cams on the correct cam gear?

I had my 4.5 engine apart, with the head and cam off. I wasn't too worried about having the timing chain out of the way. I just lined up the marks afterwards, turned it by hand several times to make sure nothing was hitting and it has been fine since.
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  #3  
Old 08-07-2004, 12:58 PM
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Quote:
Originally posted by joshhol
I'm not a pro, but couldn't you remove the rocker arms allowing the valves to close?

Are there timing marks on each cam you could use to line up the balancer with afterwards to get the cams on the correct cam gear?

I had my 4.5 engine apart, with the head and cam off. I wasn't too worried about having the timing chain out of the way. I just lined up the marks afterwards, turned it by hand several times to make sure nothing was hitting and it has been fine since.
i dont think it has rocker arms...
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  #4  
Old 08-07-2004, 01:10 PM
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I'm not familiar with that engine.

What does the cam ride against pushing the valves down then?
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  #5  
Old 08-07-2004, 01:19 PM
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Quote:
Originally posted by joshhol
I'm not familiar with that engine.

What does the cam ride against pushing the valves down then?
shim/bucket assembleys i believe....any ideas?
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  #6  
Old 08-07-2004, 01:25 PM
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Sorry man, I'm really not the one to give you advice here although I wish I could. I'm more familiar with ancient Benz technology.

Did you search the archives on this site?

Here are some thoughts though. I leave it up to you to take them with a grain of salt as I am not a technician by any means.

How many teeth did you jump on the exhaust cam? Could you bunch up the chain enough to slip the cam back a tooth or two in the other direction? Enough to compensate for whatever you missed. Are there timing marks on the cam towers to get you back in synch after all this tinkering has been done. You don't want to loose cam timing with no reference.

It sounds like the valves are hitting the pistons, so use care when trying to turn the engine. And don't try to turn it backwards.
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  #7  
Old 08-07-2004, 02:19 PM
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Steve,

first of all: don't panic! 8)

Quote:
instead of gliding smoothly round,
As far as I know, this thing never ever glides smoothly, at least not when we changed the (sigle row) chain of the 2.3-16 some weeks ago.

Instead of gliding the hole thing snaps (hope you understand my poor English).

Quote:
the chain slipped over the exhaust cam (the one on the left as viewed from the front) whist still turning the cam on the right of the engine (as viewed from the front)
You should really get another pair of helping hands for the rest of your adventure.
If I got it right, the chain was in contact with the intake cam but jumped one tooth (maybe two) on the exhaust cam.

To correct this you have to turn the exhaust cam clockwise to get the chain wheel one tooth ahaed. Take an open 25mm wrench to turn the cam direktly behind the chain wheel.

But: maybe the chain from the intake side fell into the chain cover and is blocking at the wheel down inside? Try to pull the (new) chain backwards out of the chain cover. Do not turn the engine counterclockwise...

If this doesn't work because something blocks the hole thing (valve sitting on the piston) try to turn the exhaust cam counterclockwise to get the system loose again.

You should manage to turn the engine and the cams even if one cam or both cams are not absolutely adjusted. After feeding the new chain completely into the engine and pressing the new link into the chain you have to align the cams.

To do that, take the distributor cap away, turn the engine until UDC of cylinder no. one.
There is a little hole in each chain wheel. Both holes must face each other for correct alignment, looking something like "O- -O" if you look from the front of the engine (the "-" indicates the position of the hole).

If one wheel is not aligned, just lift the chain (tensioner still out) and turn the cam until it fits.

good luck,
bis denn,
Christian

1989 300TE
1984 2.3-16
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  #8  
Old 08-07-2004, 02:55 PM
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right, i tried playing with the cams/crank to realign them so I can continue to feed the chain in but I cant move them now, I assume this is because something is touching down below. I think it skipped more than 1 or 2 teeth.....

It seems stuck where it is....

If I take the cams out (which isn't a bad thing because not only will it hopefully solve this problem but I can do my valve clearance as well) how do i reset everything?

Do you line up the crank with the timing marks on the case (where the hell are these anyway!) then align the cams as you said above then reconnect the chain?

whats the torque spec for the cam bolts?

thanks again!

steve
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  #9  
Old 08-07-2004, 03:18 PM
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steve,

so if nothing helps, you should take out the cams...

Aligning is simple, you need the distributor finger at cylinder no. one, you need the crankshaft with piston no. one at the top end and you need the cams aligned as described above.

If you look to the pulley on the crankshaft, there are marks on it (20, 10, 0, 10, 20 and on) and there is a pin on the chain cover indicating the angle. You have to position your head where the pipe of the air cleaner used to be, looking from two 'o clock to the center...

Turn the engine until the distributor finger roughly points to where the cable to spark no. one is and slowly turn on until the pin at the chain cover points to 0 or OT. Set the cams and that's it.

Torque for the cam bolts is 21Nm, tighten them step by step over the cam bearings because you will open some valves.

I'm here tonight (working on my speedometer) if you have further questions.

BTW what happend to 190revolution? Hacked again? Do you know any alternatives?

bis denn,
Christian

1989 300TE
1984 2.3-16
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  #10  
Old 08-07-2004, 04:47 PM
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right, an update...cams are out!

I removed the inlet cam first, no problems. On the exhaust cam I had to remove the SLS pump at the end, other than that, no problems.

The engine now turns over freely!

The chain is half in, half out, its dark now so it'll have to wait till the morning.

Just so its clear for the morning, I have to now:

Complete threading new chain through. Set crank to TDC, rotor pointing at notch in distributor. Install cams so the 2 dots face each other. install top guide rail. connect ends of chain together. install tension.

to clarify:

engine bay at moment:


cams and stuff


dots line up like this?


is this the notch I line up?


TDC for the crank is down there somewhere? what about the mark in the case to line up with, where is that?


thanks for your help
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  #11  
Old 08-07-2004, 05:32 PM
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Steve,

Quote:
The chain is half in, half out, its dark now so it'll have to wait till the morning.
So you'll complete it tomorrow!

Quote:
Complete threading new chain through. Set crank to TDC, rotor pointing at notch in distributor. Install cams so the 2 dots face each other. install top guide rail. connect ends of chain together. install tension.
so far: nearly perfect.

It's not the notch the rotor should point to, its the small line in the lower left of the ring (where the notch is in). Are you with me?

Just put the cap back on and look for the position of the no. one spark lead. The rotor should point in that direction.

Quote:
dots line up like this?
exactly!

Quote:
TDC for the crank is down there somewhere? what about the mark in the case to line up with, where is that?
I can't see the pin on the chain case
should be behind that cable for the magnetic coupling...

read you tomorrow!
bis denn,
Christian

1989 300TE
1984 2.3-16
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  #12  
Old 08-07-2004, 06:48 PM
Brian16V
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Aren't there plastic timing chain gude(s) down in there somewhere? Could it be the chain is getting hung up on those? I think you ought to look at an illustration to view the actual timing chain path. Not much help, but it's another thing to think about. You're also right in not trying to "force" anything.

Brian
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  #13  
Old 08-08-2004, 07:10 AM
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right, sunday morning update.....

have completely fed the new chain in and disconnected it from the old one.

I then turned the engine over till the O/T mark on the crank lined up with the pin on the crankcase (found the pin at last... ) like this:


At the same time the O/T mark is aligned, the rotor arm is pointing here - although its not pointing directly at it its pretty close? Is that ok?: (i also found the correct notch-cheers chris!)


Also, when I put the distributor cap back on the rotor arm lines up (roughly) with lead number 1

Does this all look ok for far?

I now reinstall the cams (dots aligned) and connect the chain yes? Then top guide rail then tensioner?

Phew, this is tough going......

thanks everone.
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  #14  
Old 08-08-2004, 08:36 AM
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Steve,

Quote:
I then turned the engine over till the O/T mark on the crank lined up with the pin on the crankcase (found the pin at last... ) like this:
You got it. That's the pin.

Quote:
At the same time the O/T mark is aligned, the rotor arm is pointing here - although its not pointing directly at it its pretty close? Is that ok?: (i also found the correct notch-cheers chris!)
That looks ok.

Quote:
I now reinstall the cams (dots aligned) and connect the chain yes? Then top guide rail then tensioner?
So far everything is fine.

When everything is together again (except for the sparcs) and before you start the engine - turn it twice by hand at the crank to make shure everything is smooth and nothing blocks. You never know.

Take care with the tensioner, push the inner part (bolt) out (towards the engine) and set it in from the outside again. Otherwise you will block the chain with too much tension... New alloy rings for the tensioner are a good idea.

all the best,
bis denn,
Christian

1989 300TE
1984 2.3-16
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  #15  
Old 08-08-2004, 10:15 AM
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right, phew....

cams are both in and torqued down.

chain is connected with new link

install top guide rail and tensioner next. then properly connect new link and turn over by hand to make sure all ok?

dots aligned ok?


new link look about right - its not peened yet just in case I needed to adjust it any more? The chain is pretty tight between the 2 cam sprockets, I hope it gives enough to install the rail.....any thoughts?


thanks; nearly there

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