190e Timing Chain Pre-Tensioner + guide rail

[JamieD]

notied the comments about the timing chain pre-tensioner in a thread below. I'm in the middle of taking a 190e 2.0 to bits, and the chain pre-tensioner has come out as 1 unit... I was expecting it to come out as several components...

Is this normal, and is there an easy way to separate the parts to re-set them before I put it all back together again?

also - would any one know a good trick to getting out the pins that hold the upper chain guide rail in place? have tried various sized bolts in there but nothing will get a good enough grip...

 

[flagstaff]

it doesn't matter that the timing chain tensioner comes out as one piece; what is important is that you put it back together correctly. make sure that you install the timing chain body first, and then fit the tensioner plunger afterwards. it will often require a sharp tap to get the ratchet to engage. after that, tighten to the correct torque. whatever you do, DON'T install and tighten the whole assembly together, as you may well snap or stretch the timing chain. have a look at this site - it's for the later m104 6cyl motor, but the section about the timing chain tensioner is the same for both:

http://www.mercedesshop.com/Wikka/M104HeadGasket

as regards the pins holding the guide rail, the best tool is a slide hammer. this basically allows you to insert a bolt into the pin, and then use a weight impacting against a stop to extract it. slide hammers are relatively inexpensive (about GBP 20), and although you may only ever need it for this job it could save you a lot of heartache. if you don't want to buy a slide hammer, then you need to work out the principle behind the pins' installation (interference fit) to get them out. it can be done with an M8 bolt and a bunch of washers, but imo it's much easier just to get a slide hammer.

 

[flyingtech55]

6mm thread on chain guide pins. I bought hardened steel bolts and used nuts washers and 3/8 square drive socket as a spacer.

Tip:- Clean out the dirt from the middle of the pins using aerosol cleaner then cotton buds etc. to ensure that the the bolt can be screwed fully home. You don't want to strip them.

Also remember to remove the 13mm bolt front right-hand side of engine (looking in from front) that isn't mentioned in the Haynes manual if you are lifting head.

HTH

Tim

 

[JamieD]

thanks for the tips - I'm trying to get the head off at the mo but the bolts aren't playing fair... is it a standard torx 55? it looks like there are double the amount of spliney bits... is this a merc special tool?

 

[flyingtech55]

Its a M12 spline drive not Torx. The head comes off with both manifolds still fitted.

Set engine to TDC timing marks.
Remove bolts securing down pipes to exhaust manifold.
Remove rocker cover, radiator, shroud, serpentine belt etc.
Slacken and remove ten (10) spline drive bolts from head.
Slacken and remove one (1) 13mm bolt from right hand top corner of head.
Remove pins from chain guide.
Slacken and remove bolt from end of camshaft.
Remove sprocket from camshaft.
Slacken and remove three (3) 6mm cap head bolts and washers from timing chest.
Lift head.

The head bolts are pretty tight. I used a Snap-On M12 spline drive 1/2" square drive bit with a four inch extension and a 24" breaker bar. Bolts 'cracked' fairly easily.

The bolts are re-torqued in three stages. 55nm (IIRC) all round then 90 degrees then 90 degrees.

HTH

Tim

 

[JamieD]

thanks for the info - glad I stopped when I noticed the weird shape... already snapped 1 3/8 extension rod on the job so far... not to mention loosing the timing chain down a dark hole...