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  #1  
Old 10-16-2003, 11:45 AM
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420sel intake system

I just acquired a '86 420sel. My mechanic recommends overhauling the intake system. He wants to take it out changing all the o-rings, air tubes, and sending the intake to a machine shop to get it all the air passages clean and make sure it's straight. All at a cost of $1600.

Is this an easy job to do by oneself? The car is 125k in mileage and 18 yr old. He said that the hoses have all hardened and the o rings the same. These make the system prone to air leak. I do know that he is trying to create more work and increase his income. In his defense, he does not cut corners when he rebuilds these engine.

What do you guys think?
John
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  #2  
Old 10-16-2003, 01:27 PM
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Location: Gainesville FL
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There is another lengthy thread currently about "how troublesome were MBs" or some such...

Your technicians logic is going to quickly make that free MB one of the most troublesome cases on the internet.

If its not broke don't f with it. So much cautious maintenance projects, indicate a lack of ability to identify the problems. The intake almost never leaks between the halves (until someone reseals them). The injector seals, idle air plumbing, and swirl chamber seals can easily be done from the top and the cost is small as the labor should not be much.

If you get ten grand in the top end of that free 420 you will have used up your freedom. Treat the rest of the car that way and in a year or two you will be telling the world how expensive MBs are.

It really doesn't do much good to built builtproof engines if you redo everything at the first failure.
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Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician
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  #3  
Old 10-16-2003, 01:54 PM
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Join Date: Apr 2000
Location: Falls Church, VA
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You didn't say if there were any problems prompting this recommendation. If you are having idle problems like surging or stumbling, or a failed emissions test, then looking for vacuum leaks and replacing the injector seals and air hoses makes sense. Otherwise, count your blessings and save your money.

I say this from personal experience. I just finished re-sealing the intake manifold on my 380 on an indie's advice and about all I can say is that it was a lot of work for no benefit.
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Chuck Taylor
Falls Church VA
'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe
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  #4  
Old 10-16-2003, 04:48 PM
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Thanks for all the help

Thanks for all the advice. I am just going to do the necessary thing ie the cam on that car and the timing chain that rattle. As for the rest, it will have to wait until other problems arise.

John
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  #5  
Old 10-16-2003, 05:58 PM
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Join Date: Oct 2002
Location: Colorado Springs
Posts: 481
I replaced all my rubber on my 560 including injector seals and the air mass flow housing for @$200 and about 5hours of my time it is a simple diy.
m
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Martin Ingram
Colorado Springs
2005 320 CDI
2006.5 VW Jetta TDI
1991 560SEL (179000 Sold)
1972 280SEL 4.5 ('The Lead Sled' 320000 miles when sold.)
1972 220D (225000 when sold)
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  #6  
Old 10-17-2003, 01:38 PM
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update

Well, the mechanic fixed the camshaft and camtower on the passenger side. He checked compression on that side and all were greater than 150psi. He adjusted all the valves on both side and triple checked them. He bypassed the car fuel injection system with an external fuel injection(I am not sure what this is?) The car ran fine with good idle. When the car fuel injection was hooked back up, there is still a rough idle, but the car revs well. He still think it't the intake system and recommend replacing the injectors.

At this point should I replace all the injectors and all the o ring and service the intake?

John
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  #7  
Old 10-17-2003, 02:01 PM
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You are not getting much technical advice from this technician. If you are a hobbiest then you might take this approach.

A real technician will tell you what is wrong. New injectors might be a good shot gun on that car having sat for a while. But a good tech should have no problem proving an injector bad and deciding whether that is your problem.
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Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician
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  #8  
Old 10-17-2003, 02:40 PM
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Join Date: Jun 2001
Location: CA
Posts: 531
Pictorial

If you want an exhaustive pictorial on how to fix intake leaks, check my web site - I did this on a 380 engine, your 420 will be very similar.

Click here.
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