Timing chain replacement
11-10-2005, 10:08 AM
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Timing chain replacement
I own a 1991 420 SEL with 139,000 well maintained miles. I've been advised to replace the timing chain now, as I am told that they often break over 100k mi. Any experience or advice here please?
11-10-2005, 02:50 PM
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I just replaced the timing chain on my 92 500SEL.
The timing chains stretch, and the inspection is to measure side deflection (with the chain out of the car). The spec is something like 8", and mine had about 2 feet, so it was definitely due.
The other primary wear component is the rails (and possibly the tensioner). On the 500 motor, there are about 8 rails, and I imagine the 420 is similar. The wear on the rails (the plastic coating coming off) is the reason that the chain gets noisy and sloppy. In my case, the tensioner was fine (at 116k miles), but the chain was worn out, and the rails were totally shot.
You want to find a qualified mechanic (or dealership) to do this work, as it is a couple of hour job with the correct special tools, and an 8+ hour job without the special tools - and if you get it wrong there can be catastrophic engine damage (and if you get it not quite right the motor will run funny, surging and down on power...)
I paid about $700 total (for chain, all rails, and install).
My engine was like a new motor when it came out - smoother, faster, etc.
-David
92 500sel (166k miles, 8+ condition)
94 SL600 (32k miles, near mint)
The timing chains stretch, and the inspection is to measure side deflection (with the chain out of the car). The spec is something like 8", and mine had about 2 feet, so it was definitely due.
The other primary wear component is the rails (and possibly the tensioner). On the 500 motor, there are about 8 rails, and I imagine the 420 is similar. The wear on the rails (the plastic coating coming off) is the reason that the chain gets noisy and sloppy. In my case, the tensioner was fine (at 116k miles), but the chain was worn out, and the rails were totally shot.
You want to find a qualified mechanic (or dealership) to do this work, as it is a couple of hour job with the correct special tools, and an 8+ hour job without the special tools - and if you get it wrong there can be catastrophic engine damage (and if you get it not quite right the motor will run funny, surging and down on power...)
I paid about $700 total (for chain, all rails, and install).
My engine was like a new motor when it came out - smoother, faster, etc.
-David
92 500sel (166k miles, 8+ condition)
94 SL600 (32k miles, near mint)
11-10-2005, 08:19 PM
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Thanks David, That is good to know. I instructed my mechanic, who specializes in Mercedes, to repace the chain. He said he had just replaced the one on his 560SEL. With 135K miles, I feel better doing this. I sensed a bit of unevenness inthe car's performance in the last few months, which could be a sign that the chain was loose. The quote I got was in the range of $600-700. I appreciate the reply.
11-10-2005, 08:45 PM
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1987 300SDL aka the "Money Pit"
For an M116 I am kind of surprised the chain went almost 140k miles. Those engines are known for snapping the chain at the 100k mark. The M117's are more durable.
I'm not sure why though maybe the guide design?
I'm not sure why though maybe the guide design?
11-11-2005, 09:26 PM
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Originally Posted by Hattaresguy
For an M116 I am kind of surprised the chain went almost 140k miles. Those engines are known for snapping the chain at the 100k mark. The M117's are more durable.
I'm not sure why though maybe the guide design?
I'm not sure why though maybe the guide design?
