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1990 500SL, 1990 V12 XJ-S, 1996 DB7 I6,
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7 Posts
Discussion Starter #1
My 1990 500SL 100,000 miles, had a coolant leak, so we decided to lift both heads and replace the gaskets. No unpleasant surprises thankfully. The leak was a dead gasket. Everything else showed little wear. The usual plastic/rubber bits broke or were replaced.

Then we noticed the cam timing was not what we expected, with each cam a little more retarded than the previous one along the timing chain. We quickly realised the chain was very tired, and frankly we were really lucky there hadn't been a very expensive woopsie. Chain, tensioner and top guides have now been replaced. All cogs were OK.

There was no chain noise or any other warning like I have experienced with other worn chain engines. There doesn't seem to be a schedule to replace the chain. I believe I have been very lucky to have caught this chain before a very expensive failure.

I can't even think of a way to detect this chain wear. Maybe measuring the position of the chain tensioner ... Maybe a stethoscope could have picked it up.

Food for thought ...

Dave
1990 500SL
1996 DB7
 

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1995 MB 600SL, !982 G-Wagen 280GE, BMW 1150RT
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84 Posts
Dean

You remember I have a 600SL and a Swedish friend who is regarded in our MBCSA club as knowing a lot asked me as to the kilometers on my car and when i replied that it is only 110 00 he immediately asked me if the timing chain has been changed as on the v12 this chain breaks without notice on 98 000 to 105 000 km. He even suggested that I don't drive my car to the mechanic, but have it loaded on a truck because this timing chain "will break" very soon. What are your thoughts, is this a double chain ? How long should it last ?
 

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Outstanding Contributor - Always Remembered, RIP
Zotye Auto 1.5T T600 2016
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90k
 

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1995 MB 600SL, !982 G-Wagen 280GE, BMW 1150RT
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84 Posts
Eric

Surely a double chain on a high performance V12 Mercedes should last longer than a rubber timing belt on a VW Golf ?

In changing this chain what is opened on the engine and what else should be changed or replaced ?

Rudi
 

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Outstanding Contributor - Always Remembered, RIP
Zotye Auto 1.5T T600 2016
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Eric

Surely a double chain on a high performance V12 Mercedes should last longer than a rubber timing belt on a VW Golf ?

In changing this chain what is opened on the engine and what else should be changed or replaced ?

Rudi
A Belt only comes into contact with the ribbed pulley and tensioner. But the chain is in contact with the guides full time and therefore is exposed to greater wear than a belt.

Normally it is a case of open the crankcase and change the chain/guides/tensioner. Much will depend on how well the car has been serviced and which type of oils have been used.

I have often found that a car has had major repairs and the old tensioner has been put back in, not a good idea. On newer engines like the 273 the old tensioner has been so designed that it travels to full length when removed and therefore a new one MUST be used, to me this is only a good thing.
 

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1995 MB 600SL, !982 G-Wagen 280GE, BMW 1150RT
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84 Posts
Thanks for the explanation Eric.

Is this a normal maintenance item on the maintenance schedule of these m120 engines ?

Can this be done without removing the engine ?

Should the cylinder head gaskets also be replaced as a matter of maintenance ?
 

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Outstanding Contributor - Always Remembered, RIP
Zotye Auto 1.5T T600 2016
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Not sure about schedule maintenance but I am going from experience with both the 119 and 120 engines and it can be done in situ but very difficult so much better with engine out.
 

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A streteched out of spec timing chain at 100k on a 119 motor would be unprecedented. Maybe if the oil was never changed. Far more likely that it was bad diagnosis or previous tampering.
 

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'93 600SL , 2009 C350
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184 Posts
Rudy I would be digging into that a bit more ... I have a 600 and have read nothing about doing the chains on these ... and most have a couple hundred thousand kms on them. But I am going to go looking for that string ... LOL
 

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'93 600SL , 2009 C350
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184 Posts
PS - I have 125,000 on mine. Have you done your wire harness?? If not, forget about the distrib and rotor .. it's probably electrical breakdowns elsewhere in the system. :eek:
 

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Outstanding Contributor
1997 SL600 Brilliant Silver Sport with grey/dark metal interior, 234K miles
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I have 173K miles on my '97 SL600 and it STILL sounds like a sewing machine at idle (no vibration, no noise).
 

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1995 MB 600SL, !982 G-Wagen 280GE, BMW 1150RT
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84 Posts
Well, you guys are giving me the best Christmas feeling.

I have changed the wiring harness and one throttle body (ETA) and hoped that that was the only shortcoming of this great car. When I was told about a timing chain change at 100 000 Kms I seriously considered getting rid of it, but now it seems many happy kilos await me.
 

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'96 SL500, Triple Black
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1,650 Posts
Well, you guys are giving me the best Christmas feeling.

I have changed the wiring harness and one throttle body (ETA) and hoped that that was the only shortcoming of this great car. When I was told about a timing chain change at 100 000 Kms I seriously considered getting rid of it, but now it seems many happy kilos await me.
I have never heard of a timing chain being a common issue with the R129. Some of the R107's, yes. Too many of these with many miles with no problems.
 

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Departed 1998 SL500 (and the Pano is in Bogota)
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11,121 Posts
The R107 had the single chain stretching problem, but MB solved it by switching to double chain. So the R129 benefited from that lesson.
 

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2012 E350 CGI Avant Garde Sport
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I'm going to wade delicately into this one and if you don't agree, well you're entitled to your opinion.

I owned MB diesels for years and with a diesel timing chain replacement at 100K was a maintance issue due to performance not breakage. I then bought a 380 SL that had a brand new engine due to timing chain breakage.

I bought a W140 S500 (okay it's really a 500 SEL...picky picky) that had 140K on it. I imediately took the car to my mechanic and told him to tidy up some maintance issues as well as change the chain, tensioner and guides. After he finshed laughing he asked me if I was sure about the chain and guides and I said yes. He said you know that it will be around $1200? I said yes. When it was ready I paid the bill and drove away. About 6 months later when I was in for an oil change he told me he had his S500 (a year newer than mine) sitting in the shop because the chain had broken and that the parts (including the chain...hehehe) were going to be around 2 grand and the engine would have to be completely torn down.

Now, I'm not even going to get into the issue of the durability of the chain, however, the guides are made out of plastic that becomes brittle with age. If they break they can become jammed in the chain and BAM! Massive engine repair!

Now you can do whatever you choose, but I have the chain replaced on both of my Mercedes at 100K. To me it's just preventative maintance.
 

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One of the BW Old Guard/R129, W204 Moderator
1997 SL500- 40th Anniversary
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7,166 Posts
The R107 had the single chain stretching problem, but MB solved it by switching to double chain. So the R129 benefited from that lesson.
Only on 1981-1983 USA import 380SLs. ROTW had dual chains on the 380, like every other 107 before and after.
 

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2012 E350 CGI Avant Garde Sport
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It was also the 1981-83 380 SE, SEL, SEC and the SL


FWIW my 380 SL with the broken chain was a 1984 model. All timing chains can and will break
 

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1990 500SL, 1990 V12 XJ-S, 1996 DB7 I6,
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7 Posts
Discussion Starter #20
Well I'm kind of relieved more people are confirming chains can be at end of life at 160,000km or less. I was beginning to think my car had a dubious history. When I started this thread I was intending to give readers a heads up that their chain should be checked. I certainly will change the chain at +100,000km mark. (If I still have it).

My chain was dangerously close to faulre (@160,000km), There was no audible noise whatsoever. My only suggestion would be to attempt to measure the tensioner position or use a stethoscope. Genuine new chain, tensioner & 2 plastic top guides came to US$425 (carpartsdiscount.com) The chain can be replaced with the engine & heads in place. A tool to "splice" the new chain onto old chain & then join ends is required.

Now my car is back on the road. The improved cam positioning has given me a measurable (through the foot) increase in low rpm torque and higher rpm power. Even the transmission seems to be happier, changing down almost as soon as I give the car some extra juice. I used to stir the transmission manually to find the right gear.

I'm a happy owner again
 
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