Applies to the following chassis: 111, 108, 109, 107, 116, and 126. Includes 3.5, 4.5, 350, 380, 450, 500, 420, and 560 V8 engines from 1970 to 1991.
When Mercedes introduced their small 3.5 liter V8 in 1970 it was hailed as a technological breakthrough in automotive engine design. That same basic design was produced for over 20 years right up to the early 1990s.
The engine itself has proven to be very robust and if maintained properly will run strong for well over 300,000 miles. Time has proven though that these engines do have an Achilles heel and if not attended to with preventative action failure can lead to catastrophic results.
The weakness I see with these engines lies in the valve train. That includes the camshafts, rocker arms, valves, and the chain mechanism that drives them. As these engines age (time not mileage) I am seeing more and more valve-related problems showing up in my shop. In the past three months, I have had to repair two different V8s that suffered catastrophic engine failure due to the failure of some cheap plastic parts in the valve train. One of the cars only had 75,000 original miles on it. When I say a cheap part I mean under $10.00! In both cases, the pistons came up to hit and bend the valves. Repairs in each case required very expensive engine tear down and reassembly.
If it seems I am trying to scare you, yes I am. For instance, if a timing chain failure occurs at high engine speeds the engine can be completely ruined. I saw one 420SEL that had the camshaft and the cam towers blown right through the aluminum valve cover. I decided to write this manual for the V8 owner, first to alert him or her to the potential problems and then to explain in detail the steps that should be taken to protect their engine for a long and healthy life. If after reading this manual you do not feel confident completing the repairs yourself, you will at least be armed with the information to take it to your favorite Mercedes mechanic and discuss with him your need for preventative maintenance in this regard.
TABLE OF CONTENTS:
- Chapter One: Replacing camshaft oiler tube clips
- Chapter Two: Replacing timing chain upper guide rails
- Chapter Three: Replacing timing chain and tensioner
- Appendix: Bonus: Adjusting valves on early V8s
This manual is 31 pages in length and has over 100 pictures to guide you through all the above repair procedures. It is bound with a smudge-resistant plastic cover. This may be some of the best preventative medicine you can get for your V8.
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