Success (timing chain,etc) - 560SL - Thanks Everyone

[Strife]

I've just completed major work; all timing chain stuff (upper guides, tensioner, tensioner arm, chain), oil tubes, valve cover gaskets/washers, belts, hoses, water pump, and (the right MB) antifreeze. All work was done preventatively (at 87.5K on a 19-year old car). I did significant cleaning of the engine compartment also (there had been valve cover leaks for a long time). All linkages were lubricated with ATF. Other than some of the belts, I saw no evidence that the parts that I replaced had ever been replaced before. Although the water pump probably had another 10-20K available, the rest of the parts were tired; the guides were very brown and one of them was grooved; the tensioner arm in particular was very grooved, to a depth about 1/3 of the plastic thickness. Very disturbing in particular was the condition of the tensioner. Compared to my new one, it would squirt oil out with hand pressure; the spring was also noticeably weaker than that of the new unit. I posit that this failure alone probably causes most system failures; the tensioner spring alone can't react fast enough to the acceleration of the chain and gets weaker with age and use; the chain starts slapping the guides, breaking them and then eventually a piece wedges in or the chain jumps. The reason I embarked on this project was that I was starting to hear "funny noises" for a few seconds as the engine started cold.

I think that the plastic guides are Nylon. Nylon contains water, and is known to become brittle when dried out; I think over time oil replaces the water content. I cut a notch in an old guide and it is brown through and through.

I used a "chain cover" fixture made for this engine to hold the chain during the cutting/pulling process and the "screw type" pin puller. Although they are not cheap, I would recommend these professional tools to anyone who values their free time. They are useful for casual as well as professional mechanics in that they can prevent costly (in terms of both dollars and time) mistakes.

For show, I installed a pair of polished valve covers and a fan that I did over the winter. They came out nicely (I had done the air cleaner earlier); I would not recommend to anyone to polish the fan. There is a real danger of cracking it, and it seems to be made out of a metal that corrodes easily (possibly magnesium?).

Thanks to everyone for inspiring and helping me with recent or old posts - I wasn't sure that I could do this until I read these forums. Now I have a lot of extra dough - uh, to spend on my Mercedes.

[rzrob]

Liked reading your success story. I embarked on a similar, but not quite as serious project on my older 450sl. I did the water pump and fan clutch. I sort of want to attack the timing chain sometime. I'll remember your post when I eventually do.

RZ Rob

[Bondavi]

Can you tell how you replaced the timing chain? There was a writeup that I read (but cannot for the stars of me find it again) that told of using one end of the new chain on the old, and threading it along down and around.

Any tips you can give me? I'm thinking of doing mine this summer.

[ch7ckc]

Strife...you are a steely eyed MB guru.Not only do you tear into your engine and put it back together...you figured out how to get first gear start.I'm still getting up the nerve to crawl under my SL to change out the motor mounts with 3800 lbs poised over me.

Great job...keep us posted on your next project.

ch7ckc
1987 560 SL

[Strife]

Originally Posted by Bondavi

Can you tell how you replaced the timing chain? There was a writeup that I read (but cannot for the stars of me find it again) that told of using one end of the new chain on the old, and threading it along down and around.

Any tips you can give me? I'm thinking of doing mine this summer.

Well, that's the general idea...Because you have to basically take the entire accessory system off of the front of the engine anyway, I did a massive belt/water pump/hose/fluid/timing chain/tensioner/arm/guide/oil chain/valve cover extravaganza. Hopefully, I won't have to do it again for 10 years or more, given my likely miles per year. Maybe by then, I'll be too old to do it again!

I really have no excuse for not documenting it. I'm working on this right now, but I have very few pictures because the weekend I did it my wife had the camera on a school trip. In a previous life, I was a technical writer (on the theory and repair of electromechanical equipment), so I really should be able to do it. The camera is a "cheap" means to illustrate something. I once had an illustrator at my disposal and he could spend a man-month on an exploded system-level diagram on a piece of equipment. That one illustration was worth about 50 pictures! Too bad labor costs as they are combined with our disposable society have virtually eliminated this art.

As it is, I may put up some notes on some tools that I bought and used for this project on the now-available Wiki. I'm a real believer in having the right tools - not because they are "cool" and make you look professional, but because they tend to keep a casual mechanic out of trouble, whereas they allow a professional mechanic to get the job done faster (=more money).

I'm going to do the subframe and motor mounts next. If I was cautious with the engine (working with $3.00 pieces of plastic whose failure or improper installation could cause $4000 of damage), I'm even more cautious about going under a car. I generally have primary, secondary, and fail-safe systems for keeping a car in the air. I knew someone, a professional mechanic who should have known better, who wound up under a car that fell. Miraculously, he didn't break anything. But he would up in a body cast with every single bone in his torso bruised. They had him whacked out on painkillers for six months.