Hello there!!
I have a 1988 Mercedes 300D 4matic and a three years ago the 4Matic stoped working. If a apply more throtle pressure then i should the triangle started blinking (That indicates that 4Matic is working in 4Matic models) but the 4Matic didn´t Work!!
So at the time i thougt that it has better to stop the car because i could damage the transfer case and drivetrain. So the car sat about 2 years in my garage. Now i want to fix it, the engine with some new oil and battery it will work ( i am a Do it youself guy )
Now a Guy asked me 15000 euros ( about 20000 dollars ) to fix the car and replace all sensors. I wanted to him beacuse i thougt that he was ripping me off
I nedd your help, i think that the transfer case is ok but i dont Know how to do, I didint fix the car 2 year ago because i was abroad, and now i am back and want to fix it. That car is a dream its nautical blue mettalic and it has full extras i belive, i just wanna that benz in to the sunset

 

Hi Rui. That is the problem with the 4Matic. When it starts to go wrong, it means a lot of job to fix it. The sensors can be involved, but their electronic too. The fail is sometimes very hard to determine exactly.
Here are the first things to check.
- check all the fuses (better replace them all by new ones and clean their emplacement).
- check all the relays and especially the overload relay,
- check you battery as many failures start with a defective battery,
- check all the fluids and replace them: engine, gearbox, power steering, brakes, transfer box.
- put the car on a lift by the lifting pads and check the wheels one after the other: move them around to see if they turn correctly and if they are moving independently.

You may also try this:
- cut the engine, turn the key off,
- disconnect all harnesses plugs that are behind the battery


(on the picture you have the 3 main plugs to withdraw and the silver with blue fuse overload relay that can cause some problems)
- wait for five minutes
- reconnect all the plugs.
- the restart your engine.
Normally, the light on the dashboard should switch off.

You can also try this other method:
- turn off the car and contact,
- disconnect the 2 wires of the battery,
- take the battery off the car,
- wait 15 minutes,
- connect the 2 battery wires together for 1 minute,
- take them apart,
- replace the battery,
- replace the 2 wires as they should (+ and -)
- start the car.

If none of these methods work, you better see a MB specialist or even go to a MB dealer to ask them an evaluation.
4Matic system can be a nightmare if it is not fixed properly, generating unpredictable failures one after the other, and even if you are a great DIY, you may not have the right tools to fix the problem.

From the bottom of my heart GOOD LUCK Rui and HAPPY NEW YEAR!

 

A thousand thanks, i am very happy for your reply and i am going to try it. I wish you a happy new year full of Love, health, Money and that you can be able to meet all objectives.
Also do you know the price of the sensors??
Kind regards and good luck.

 

No Rui, I do not know the price, but as far as I can remember there were 3 sensors sender units, with a price for the 2 front sender units at (around) $80 each and the rear sender unit , depending if you have ASR or not, at $200 and more than $300 (but I am not 100% certain it is the same for 4matic)

As our W124 can show a lot of differences in parts references, the best would be to bring your VIN to a MB dealer/garage and ask them the price of those sensors/senders. The price does vary (sometimes a LOT!!!) between European countries. I know that I should purchase some parts in Belgium rather than in France to make a 60% economy on them. On the contrary, some parts are cheaper in France...
Good luck with the restoration of your 4matic!