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Old 11-01-2001, 10:44 AM
Posts: n/a
Question Just bought a 86 420 SEL, what to expect?

I just purchased an 86 420 SEL with about 139K on the clock. I've looked through this forum and I know that this beast gets about 17-21 MPH. It also appears that this thing has a timing chain problem too. Other than those factors, I'm still in the dark about this machine. This is my first MZB, and I'm crossing over from the "rival" do to the need to have something more practical (than a two door 318 sports coup).

The car looks to be in stellar shape. I like to do a lot of my own work, is this car easy for changing spark plugs and little nicky nacky things? Your response is appreciated.

Mateo - 86 420 SEL
- 98 Land Rover Discover (for the wife).

ps we live in snow country.

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Old 11-01-2001, 11:20 AM
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Join Date: Nov 1999
Location: Germany
Posts: 63
Believe you will enjoy your 420SEL. I have 240k on mine and still going strong. Expect to need a valve job at 200k plus a catalytic converter. If you start to use a lot of oil, go ahead and get the valve job - will run like a new car.

With as many miles as yours has, suspect timing chain has already been replaced, but no guarantees - can't hurt to check.

Only other problem with W126 is a/c problems - the Achilles' Heal of M-B. If you're going to have a big dollar expense some day, odds are it will be a/c system. Good news is once problems are isolated (monovalve, aux water pump, pushbutton unit), system will work again quite well. Others report power window and sunroof problems, but so far I haven't had any.

Believe 420 SEL is one of the star performers of the W126 class - decent mileage and great acceleration, without rear suspension problems of 560 SEL/SEC. Also believe W126 is one of best looking M-B...classic lines.

Joe B.
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Old 11-01-2001, 01:20 PM
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I think Joe covered it. Make sure you change all the fluids and filters esp. the trans.
I wonder if it's the orig. radiator? The units w/o the reinforced steel neck break over-time.
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Old 11-01-2001, 03:05 PM
Registered User
Join Date: Feb 2001
Location: BC, Canada
Posts: 378
The timing chain plastic guide rails must be checked. Search the archives here. What happens is a piece will break off and jam in the cam gear. This stalls the chain or makes it skip. Either way, it is a disaster. Less than $10 in parts to fix. When mine were replaced, they were the color of brown glass and even more brittle. The new ones are bone white. The valves can hit the pistons and break off. The cylinder walls are hardened aluminum which work great but can't survive being scratched with valve heads.
Spark plugs are a little hard to get at on the left side. You have aluminum heads which are have delicate spark plug threads. Someone here said that you should work on plugs when the engine is stone cold.
How is the steering? I have had a bunch of work done on the front and still have some wandering. Good tires that are properly balanced are key.
1967 250SL
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Old 11-01-2001, 03:46 PM
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Join Date: Aug 1999
Location: Cincinnati, Ohio
Posts: 1,937
....And since you live in snow country, GET SNOW TIRES!

Most of the foibles of the 420 have been covered already, the timing chain being of utmost importance. If a chain, rails and tensioner haven't been done already, do it right away!

Enjoy your new car!

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