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1991 350SDL 2004 G500
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528 Posts
Discussion Starter #1
Going to give you guys the full back round on this one, otherwise skip to the bottom.


I've come to realize that all of the problems with my car lately (Two broken belts last year, belt shock, power steering...) seem to all be related to one or two previous repair jobs from my mechanic.

The first was when the belt pulled a whole in the front engine cover, it was repaired but a small leak of oil still remains because the gasket was not done correctly.

The second was the harmonic balancer (I will never forget the noise that it made.....) The job was done, but within a day the noise came back because the pin fell out...I brought it back right away and its been fine ever since.

I noted in a previous thread that my power steering wasn't working properly when I turned the wheel too far. The fluid was a little low, but topping it off did nothing, so a little more investigation (And a sudden noise that started up) pointed to the crankshaft pulley. My old mechanic was good but some of the monkeys that worked for him certainly messed things up, unfortunately he's moved on and I'll be doing this job myself.

So in the end the question is what will I need to do in order to fix the crankshaft pulley?
 

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1991 350SDL 2004 G500
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528 Posts
Discussion Starter #2
Took half of the front end apart but we figured it out, the key for the crankshaft pulley broke in half. Obviously my mechanic did something wrong. Any ideas how the key broke the way it did and how I can prevent it before I put the new one in tomorrow?
 

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1987 420SEL
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1,133 Posts
I reckon some pictures would help a bit, but I personally have no idea how something like that could happen unless there was some sort of huge resistance against the pulley.

I know that on a lawn mower there is a key that breaks to let the fly wheel keep spinning if one were to hit a large rock or something solid that would make the crank stop abruptly. I'm not really sure how this would pertain to your situation though...
 

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1991 350SDL 2004 G500
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528 Posts
Discussion Starter #6
All of the other pulleys are turning freely (we cleaned them while we were there) Does anyone know if the harmonic balancer is the same on the 350SDL as it is on the 300SDL/300D? Is it possible that they bought the wrong balancer for the engine?

(This is a 350SDL with an engine from the a 1987 300D)
 

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CH4S Admin , Outstanding Contributor
1985 500SEC, 1991 190E 2.6.
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40,145 Posts
I am not familiar with diesel cars, but an online search for the harmonic balancer and comparison of the part numbers should clear up the question.
Cheers
 

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1991 350SDL 2004 G500
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528 Posts
Discussion Starter #8
I checked earlier and I found that (thankfully) the harmonic balancers are the same. What in the world is causing the key to split in half? (All of the aux. fine and turning freely)
 

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2005 SLK350, 91 300SL with Pano Top, 04 S500, 2015 Tesla Model S
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2,084 Posts
The key could easily break in half if the bolt holding the pulley to the crankshaft is not torqued down properly. In other words, only a slight looseness would break it due to the engine torque.
 

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1991 350SDL 2004 G500
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528 Posts
Discussion Starter #10 (Edited)
I've read around and I keep getting conflicting numbers on the proper torque but the consensus is "around 200 foot pounds" can anyone verify?


And this just in (which is scary) We dropped the key and while fishing for it in the oil pan with a magnet we pulled out a number of small ball bearings....
 

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1991 350SDL 2004 G500
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Discussion Starter #11
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