Common Mercedes Problems & Solutions (2024)

Table of Contents
Featured Problems & Solutions Fixing the Tilting Sunroof Testing Diesel Fuel Injectors for Peak Performance Ignition Tumbler / Key Wear Determining Parts Needed for Loose 126 Front Suspension Malfunctioning Non-Tilting Sunroof Solutions Finder: Body and Exterior Trim ProblemsView All Malfunctioning Non-Tilting Sunroof Badly Oxidized and Faded Aluminum Window Trim Fixing the Tilting Sunroof Brake ProblemsView All How to Diagnose Common Brake Troubles Replacing Worn or Damaged Brake Mechanical Parts Flushing Old Fluid and/or Excessive Air Out of Your Brake System Climate Control ProblemsView All Intermittent Cabin Heat - Second Generation Climate Control Intermittent or No Cabin Heat - First Generation Climate Control Heater Blower Motor Won't Run Driveline and rear end ProblemsView All Drive Line Flex Disk Deterioration and Catastrophic Failure Avoiding 201 and 124 Chassis Flex Disk Trouble Diagnosing and Repairing Common 114 115 107 116 123 and 126 Rear End Problems Electrical ProblemsView All Diesel Engine Glow Plug Timer Relay Failure - Options for Repair Troubleshooting an Electrical Problem O.E. Aluminum Fuse Failure Engine ProblemsView All Finding the Best Diesel Performance Upgrade 1984 to 1995 601 602 603 Diesel Performance Enhancement Increasing Turbocharger Performance on Diesel Engines Fuel Delivery ProblemsView All Testing Diesel Fuel Injectors for Peak Performance Fuel Restriction at the Internal Fuel Tank Filter Screen Diesel Engine Fuel Leaks Interior ProblemsView All Inside Door Related Problems Ignition Tumbler / Key Wear Broken Down or Sagging Front Seat Bottom Lights ProblemsView All Preventing Rust from Forming Inside Your Headlights What to Do with Rusty or Faded Tail Light and Fog Light Reflectors How Can I Easily Restore My Euro Headlights? Rust / Corrosion ProblemsView All Miracle Rust Repair for Your Old Mercedes Rocker Panel and Floor Permanent Rust Repair without Welding Welding in New Sheet Metal When Repairing Rust Out Suspension ProblemsView All Determining Parts Needed to Fix Loose 123 Chassis Front Suspension Determining Parts Needed for Loose 126 Front Suspension Diagnosing Loose Front End Steering Transmission ProblemsView All Diagnosing, Adjusting and Fine Tuning Mercedes Automatic Transmissions Automatic Transmission Erratic Shifts Transmission Oil Leaks Vacuum ProblemsView All Determining Correct 1980 to 1985 Diesel Vacuum System Hose and Line Routing 126 Chassis Sedan Vacuum Door Lock Failure 123 Chassis Vacuum Door Lock Failure SVO / Biodiesel ProblemsView All Installing a Mercedessource Diesel to Vegetable Oil Fuel Conversion Converting an Older Mercedes Diesel to Run on Vegetable Oil (SVO) Using the Mercedessource STC Kit? Running your Diesel Engine on Straight Vegetable Oil

Featured Problems & Solutions

  • Common Mercedes Problems & Solutions (1)

  • Common Mercedes Problems & Solutions (2)

  • Common Mercedes Problems & Solutions (3)

  • Common Mercedes Problems & Solutions (4)

  • Common Mercedes Problems & Solutions (5)

  • Body and Exterior Trim Problem:

    Fixing the Tilting Sunroof

    A true challenge - but you can do it with the right knowledge.

    Fixing the many problems that plague these aging tilting sunroofs can be frustrating and time consuming. As you can see from his expression in the picture, even Kent can find it challenging at times. When these sunroof mechanisms are operating properly it is a pleasure to open, close and tilt the roof. When not working properly it can be a real pain.

    Read More >

  • Fuel Delivery Problem:

    Testing Diesel Fuel Injectors for Peak Performance

    You will need a bench mount pressure release tester to do this yourself.

    Testing mechanical diesel fuel injectors isnot difficult if you have the right tools and knowledge. When you do it yourself you KNOW the job will get done right and you can save big $$$. Kent has seen so many injectors damaged by "professionals" he is convinced if you want your injectors to be set correctly and without damage then do it yourself. No one cares as much as you do.

    Read More >

  • Interior Problem:

    Ignition Tumbler / Key Wear

    There are ways to reduce it - and we have ways to fix it!

    WARNING: As time passes we are seeing more and more ignition lock failures on 123 and early 126, 201 and 124 chassis models. If the tumblers in the lock fail you can find yourself stranded and it can be expensive to get the car towed and the lock replaced. If you change it before it fails it can be inexpensive and relatively easy to replace.

    Read More >

  • Suspension Problem:

    Determining Parts Needed for Loose 126 Front Suspension

    Know what to look for and understand the parts you will need

    Applicable to all 126 sedans and coupes from 1981 to 1991. This includes the 380SE 380SEL 380SEC 300SD 500SEL 500SEC 300SDL 420SEL 560SEL 300SE 300SEL and 350SD.Front and rear suspension overhaul is almost always left until one has fixed everything else on the car. We know that most owners can live with some looseness in the suspension, especially when you consider the age of the 126 chassis.

    Read More >

  • Body and Exterior Trim Problem:

    Malfunctioning Non-Tilting Sunroof

    Nothing like a good smooth working power or manually operated non tilting sunroof (up to 1985)!

    Fix your non-tilting sunroof yourself! We have the manuals and repair kits available to get that faulty sunroof working like new again. Problems can range from burned out motors, stripped gears, damaged cables, missing or damaged slides, poor lubrication, to faulty adjustment.

    Read More >

If you have a problem with yourolder Mercedes and are trying to figure what is causing it or how to fix it, you have come to the right place.

Common Mercedes Problems & Solutions (16)

Let Kent explain how his solutions finder works: "Just select the location of the problem you are experiencing, the chassis designation of your car and a few key words and click Search. If I have written a description of the problem or one related to it, it will show up on the results page. The causes of the problem will be explained and all possible solutions we offer to diagnose and fix it will be listed. Read More

You can learn a lot about your Mercedes by just browsing through all the problem descriptions I have written related to your model. My new solutions finder replaces our old benz aid forum and tech help page. Even if you have never work on your car before it is never too late to start. With the right knowledge, tools and parts you can do it.

If you can not find your problem listed for your chassis then it has not yet been written. I am working on and adding new problem descriptions weekly. I will be adding more content on the W140, W202, W210, and W220 chassis later this year.If you have a problem that has not been addressed, send it to me as a COMMENT through our contact page describing your particular problem. I will not be able to answer these requests directly, but I will add it to my list of problems to work on....the list is not getting smaller. :-)

There is nothing quite like the feeling you get when you can find and fix a mechanical problem yourself,
Kent Bergsma

Close ^

Solutions Finder:

Common Mercedes Problems & Solutions (17)

Body and Exterior Trim ProblemsView All

Body and Exterior Trim

Malfunctioning Non-Tilting Sunroof

Nothing like a good smooth working power or manually operated non tilting sunroof (up to 1985)!

Body and Exterior Trim

Badly Oxidized and Faded Aluminum Window Trim

It can be restored but it takes a special power tool and hard work

Body and Exterior Trim

Fixing the Tilting Sunroof

A true challenge - but you can do it with the right knowledge.

Brake ProblemsView All

Brake

Replacing Worn or Damaged Brake Mechanical Parts

Fixing brakes is not difficult and can save you hundreds

Brake

Flushing Old Fluid and/or Excessive Air Out of Your Brake System

Efficient and affordable pressure bleeding, system flush and fluid capture is here for all.

Climate Control ProblemsView All

Climate Control

Intermittent Cabin Heat - Second Generation Climate Control

Applies to late 123 and 107 chassis and all 126 chassis 1981 to 1991

Climate Control

Intermittent or No Cabin Heat - First Generation Climate Control

No heat or heat all the time are common problems with 1977 to 1980 models with automatic controls

Climate Control

Heater Blower Motor Won't Run

A common problem on all models. Options for repairing it yourself and saving big $$$.

Driveline and rear end ProblemsView All

Driveline and rear end

Drive Line Flex Disk Deterioration and Catastrophic Failure

Start with inspection and replace at first signs of wear to prevent expensive damage to transmission

Driveline and rear end

Avoiding 201 and 124 Chassis Flex Disk Trouble

Watch for signs of impending failure

Driveline and rear end

Diagnosing and Repairing Common 114 115 107 116 123 and 126 Rear End Problems

The Differentials are very rugged. It is the associated parts that usually fail due to age and high mileage

Electrical ProblemsView All

Electrical

Diesel Engine Glow Plug Timer Relay Failure - Options for Repair

Here is an option to replace the pre-glow factory unit with a reliable manual controlled relay

Electrical

Troubleshooting an Electrical Problem

Unknown battery drain, electrical shorts, blown fuses - these can be difficult to isolate!

Electrical

O.E. Aluminum Fuse Failure

One of the most common problems we see on older Mercedes.

Engine ProblemsView All

Engine

Finding the Best Diesel Performance Upgrade

Injectors do not last forever. Changing over to Monark nozzles can boost performance!

Engine

1984 to 1995 601 602 603 Diesel Performance Enhancement

Quick list of things you can consider to increase performance and mileage

Engine

Increasing Turbocharger Performance on Diesel Engines

Don't just ignore your turbo charger or major problems can occur!

Fuel Delivery ProblemsView All

Fuel Delivery

Testing Diesel Fuel Injectors for Peak Performance

You will need a bench mount pressure release tester to do this yourself.

Fuel Delivery

Fuel Restriction at the Internal Fuel Tank Filter Screen

A plugged filter inside your fuel tank can lead to hard starting and power loss

Fuel Delivery

Diesel Engine Fuel Leaks

The sources of fuel leaks and procedures needed to repair them are many

Interior ProblemsView All

Interior

Inside Door Related Problems

Failure to do preventative maintenance could lead to some very expensive repairs

Interior

Ignition Tumbler / Key Wear

There are ways to reduce it - and we have ways to fix it!

Interior

Broken Down or Sagging Front Seat Bottom

D.I.Y. reinforcement kit available for 116, 123 and 126 chassis front seats

Lights ProblemsView All

Lights

Preventing Rust from Forming Inside Your Headlights

Sometimes the fix can be real simple and real cheap.

Lights

What to Do with Rusty or Faded Tail Light and Fog Light Reflectors

Tail lights we are talking all models from 1960s to Mid 1990's - Fog lights only on those with removable lenses.

Lights

How Can I Easily Restore My Euro Headlights?

You'll wonder "why didn't I do this earlier"?

Rust / Corrosion ProblemsView All

Rust / Corrosion

Miracle Rust Repair for Your Old Mercedes

Yes there is! Miracle Paint and fiberglass cloth can work miracles.

Rust / Corrosion

Rocker Panel and Floor Permanent Rust Repair without Welding

You can do it yourself without the hassle and bad side affects of welding!

Rust / Corrosion

Welding in New Sheet Metal When Repairing Rust Out

Not always the best solution as you will see here.

Suspension ProblemsView All

Suspension

Determining Parts Needed to Fix Loose 123 Chassis Front Suspension

Parts breakdown will help you find what you need fast

Suspension

Determining Parts Needed for Loose 126 Front Suspension

Know what to look for and understand the parts you will need

Suspension

Diagnosing Loose Front End Steering

Inspect the tie rod ends first for wear

Transmission ProblemsView All

Transmission

Diagnosing, Adjusting and Fine Tuning Mercedes Automatic Transmissions

You CAN do this yourself if you have the right information and equipment!

Transmission

Automatic Transmission Erratic Shifts

Proper diagnosis is priority one - then repair! DIY testing and repair kits available.

Transmission

Transmission Oil Leaks

Some leaks are not difficult to fix. Others require removal of the transmission

Vacuum ProblemsView All

Vacuum

Determining Correct 1980 to 1985 Diesel Vacuum System Hose and Line Routing

When troubleshooting your vacuum system you must know where the hoses and lines go

Vacuum

126 Chassis Sedan Vacuum Door Lock Failure

Different from the 116 / 123 chassis and more difficult to troubleshoot

Vacuum

123 Chassis Vacuum Door Lock Failure

A very common problem that requires precise troubleshooting

SVO / Biodiesel ProblemsView All

SVO / Biodiesel

Installing a Mercedessource Diesel to Vegetable Oil Fuel Conversion

We offer an easy to install kit or you can build one from our components

SVO / Biodiesel

Converting an Older Mercedes Diesel to Run on Vegetable Oil (SVO) Using the Mercedessource STC Kit?

Questions and answers to help you decide if this is right for your diesel

SVO / Biodiesel

Running your Diesel Engine on Straight Vegetable Oil

The pros, cons, effort, and expense of running your Mercedes Diesel on waste vegetable oil

Common Mercedes Problems & Solutions (2024)
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