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1997 S420
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136 Posts
Discussion Starter #1
The water pump seal on my 420 SEL let go, have so far removed all the bolts on the water pump except one which is behind the timing wheel, looks to me that the timing wheel will have to come off, if I'm going to take that off I may as well replace the crank seal, am I correct in assuming that a special tool is required to hold the timing wheel whilst taking out the centre bolt.
 

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BenzWorld W126 & W201 Host
1988 420SE, 2002 C180 Kompressor, 200 ML320
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1,159 Posts
If the front pulley oil seal isn't leaking, don't go there.

There is no need to remove the big centre bolt.

If you feel around inside the pulley, you wil find there are actually a series of 13mm bolts around the outside of the big bolt. Remove these and the pulley will come off.
 

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First the harmonic balancer comes off the crankshaft hub with 6 13mm (if memory serves) bolts. Stick your fingers in there to feel them - may be packed with goo. They are in a nonsymetric pattern so pay attention or mark the position of the balancer. To remove the hub I would use the age-old rope trick.
 

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1997 S420
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136 Posts
Discussion Starter #4
Thanks for the prompt response, yes unfortunately the front main seal is leaking a bit, I was prepared to live with it until the water pump went west and have removed so much that it is now staring me in the face, had already removed the six bolts and removed the belt pulleys, got to admit it took me a while to work that one out, with the bolt holes not being equally spaced ( didn't notice this ) the mark on the hub of the pulley's makes sense, balance wheel still seams to block the removal of the last bolt at the very bottom of the water pump, there is a notch in the perimeter of the balance / timing wheel, is this meant to facilitate removal of the offending bolt or it for the special tool for holding the wheel whilst removing the centre bolt. Have been out and purchased a new pump & front main crank seal earlier today so all ready to go if I can get the things off, anyone any idea what the special tool looks like, searched this forum, couldn't find much in this regard, does it bolt to the wheel or is it like a large " C " spanner
 

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Moderator
1991 500SEC 55K mi. 1987 560SEC Now 153K mi. 2020
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Hello hoggy,

I attempted to post the MB CD pictures for you earlier, did so, then edited one letter in my post & the pictures went away completely!

So, here is a reposting for you, with both info & pics.

Enclosed are the MB CD images regarding the front seal. Looks to me like the seal tool screws onto the front of the crank & pulls the seal into the bore. Reference is made to add some grease during the installation.

Cheers, MBL
 

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Registered
1997 S420
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136 Posts
Discussion Starter #6
Thanks for the Info, explains a lot, seems I have been barking up the wrong tree with regards to restraining the crank whilst undoing the centre bolt, the extracts you posted indicate a special tool that goes on the flywheel / ring gear ( or at least thats how I read it ) will go rummage around under the car see if I can see where such a thing would fit. The sleeve for installing the new seal using the centre bolt will work well and ensure it goes in square, will knock one of those up, thanks again for the help.
 

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1997 S420
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136 Posts
Discussion Starter #8
Great, how does the rope trick work, sounds good but familiar with the concept.
 

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Remove a spark plug of a cylinder on the compression stroke - or remove the cam followers. Then feed in a few feet of finger diameter rope, obviously leave a couple feet hanging out of the spark plug hole! Rotate engine until the piston compresses rope against the head. Engine will lock up like a rock. When done rotate engine backward a small amount to uncompress the rope and it will come out. This is much better than futzing with some tool that if not factory designed may bend the ring gear or whatever else.
 

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1997 S420
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136 Posts
Discussion Starter #10
Job done, ended up making a tool to hold the timing / balance wheel, it worked well and have attached a sketch of it and another that I knocked up to install the front main seal. All in all it's not a job I look forward to doing again, far too much had to be removed to take off the water pump, at least it didn't break the bank.Thanks again for the input
 
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