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Old 05-17-2001, 09:23 AM   #1 (permalink)
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Date registered: Dec 1998
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420 SEL Timing Chain???????

I've read, in various forums, horror stories of 420's suddenly breaking a timing chain and causing varying amounts of damage to the engine.<br>
However my mechanic says I will here it at start up and the car will give plenty of warning if I am paying attention. He even poo pooed the idea of changing it as preventative maint. Any thoughts?<br>
<br>
Thanks again
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Old 05-18-2001, 01:36 AM   #2 (permalink)
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Re: 420 SEL Timing Chain???????

Change it, and the guides, around 100k miles. You do not advise the age or mileage of the car. The 420's tend to fail the guides, which causes the chain to jump time.
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Old 05-19-2001, 03:26 PM   #3 (permalink)
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Re: 420 SEL Timing Chain???????

I HAVE AN 87 420 SEL AND HAD THE CHAIN RAIL FAILURE ;THE PLASTIC RAILS GET BRITTLE AND THE CHAIN STRETCHES OVER TIME AND WHEN YOU START THE ENGINE THE STRETCHED CHAIN SLAPS THE RAILS AND THEY BREAK THUS NO TENSION ON THE CHAIN AND IT SLIPS OR PIECES OF THE RAIL GETS CAUGHT IN THE WAY USUALLY A PISTON WILL HIT AND BEND A VALVE OR TWO AND NOW YOUR OUT $4500 TO$6500 FOR REPAIRS BUT YOU WILL HEAR A PINGING SOUND FOR A FEW SECONDS AFTER STARTING WHEN IT'S ABOUT TO GO ,IT'S A SOUND I'LL NEVER FOGET I BOUGHT THE CAR WITH 114,000 MILES IT HAPPENED AT I22,000 MILES I WILL CHANGE THE CHAIN TENSIONER AND RAILS AT 200,000 MILES IT'S MUCH CHEAPER BE WARE!!!!!
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Old 05-21-2001, 06:53 AM   #4 (permalink)
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Re: Re: 420 SEL Timing Chain???????

Thank you for the replies. I have a more specific question, is it a pinging sound or more of a slapping sound? On start up this morning I lifted the hood while my wife turned the key, I heard what sounded like 10 or so slaps that immeadiately dissapeared (1-2 seconds)
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Old 05-21-2001, 07:26 AM   #5 (permalink)
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Re: Re: Re: 420 SEL Timing Chain???????

YES ;SLAPPING ,PINGING ,OR ANY SOUND YOU DON'T RECOGNISE AS A FAN BELT SQUEEK GET IT TO A TECH RIGHT AWAY OR YOU WILL BE OUT $4000 TO $6000
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Old 05-22-2001, 06:04 AM   #6 (permalink)
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Re: Re: Re: Re: 420 SEL Timing Chain???????

Re timing chain (important preventive measure to avoid total engine destruction), see links below. I had the chain, tensioner and top rails (the problem ones) replaced for $170 parts and $350 labor.<br> <br> http://www.mbca.org/MBCA_parts_wear_out.htm<br> <br> http://www.mbca.org/discussion/threadA.cfm?threadid=4033&state=General_Discussion &mysearch=lock<br> <br> http://www.*****************/shopforum/showthread.php3?threadid=6777<br> <br> http://www.*****************/shopforum/showthread.php3?threadid=16348<br> <br> http://www.*****************/shopforum/showthread.php3?threadid=10025<br> <br> http://www.*****************/shopforum/showthread.php3?threadid=9225<br> <br> http://www.*****************/shopforum/showthread.php3?threadid=7983<br> <br> http://www.*****************/shopforum/showthread.php3?threadid=7653<br> <br> http://www.*****************/shopforum/showthread.php3?threadid=6446<br> <br> http://www.*****************/shopforum/showthread.php3?threadid=7548<br>
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Old 05-24-2001, 04:48 AM   #7 (permalink)
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Re: Re: Re: Re: Re: 420 SEL Timing Chain???????

c43amg7,<br> <br> Thank you for going above and beyond by posting all of those valuable links. Now here is the twist; When I bought the car from the dealer there were maint. records in the trunk so I called the previous owner who said he changed it at 120k.<br> <br> thanks again,<br> <br> M
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Old 07-29-2001, 06:00 PM   #8 (permalink)
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Re: Re: Re: Re: Re: Re: 420 SEL Timing Chain???????

1987 420SEL also blew the timing chain at about 128k - but not at idle this time, I was doing about 40MPH. Car never ran as well after the rebuild, either. I would recommend changing the chain at every 80-100k. <br> <br> Does anyone know if this problem is as common in the 560 engine?
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Old 01-07-2003, 11:19 AM   #9 (permalink)
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Date registered: Jan 2003
Vehicle: 1986 560 SEL
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Timing chain


if you get the timing chain upgraded from the single-link to double-link you shouldn't ever have a problem. The single link system was standard before '85, the double was standard thereafter , for just the reasons that you all have described. Wether your car has started acting oddly or not, take it in to your mechanic (or a dealer if possible) and have them refit your car with the double-link timing chain. It's not cheap (I think it costs about $1000) but it's worth it.
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Old 01-07-2003, 12:21 PM   #10 (permalink)
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Date registered: Oct 2002
Vehicle: W126 420SEL, W123CE
Location: silicon valley
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Timing chain

420sel '86.
Guide broke at 146K miles; chain was OK.

After trading to an accidented '87 engine (66K, cost was $3,900 parts and labor) the car isn't as smooth as before: jumps before changing gears.
They say that it can be fixed by adjusting the bands of the transmission; but after many adjustments, it's still the same.

I completely lost interest in the car and am currently driving my wife's Cherokee...

Thanks for the advise: I will look into double-link chain when the car reaches 240K...if I still have it.

cheers,
charles
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