1991 300 TE 4Matic, great car with 200,000 miles, 4matic light on dash just lit up and it wont engage 4 wheel drive. Found hydraulic reservoir was low and added correct MBZ fluid, light flickers when engine starts then goes on full time, 4 wheel drive will not engage. Here in Sun Valley, Idaho , we have a lot of snow and I have driven over big ridges that may have rubbed the undercarriage, can't see any damage. I build Bonneville race cars and powerful engines but I don't have a clue about what to check on this car to fix the electronic computer controlled 4 wheel drive.
Can any body give me some ideas. I called the dealer's service writer and he told me to add hydraulic fluid to the coolant overflow reservoir???
Thanks to all.

* Let's hope he meant hydraulic fluid to the hydraulic fluid resservoir! How much hydraulic fluid did you have to add? Over half a liter? Can you see any signs of hydraulic fluid leakage under the hood or under the car? Check hose from reservoir to pump, body of pump itself, and under the car from the transfer case back.
* If the hydraulic system is taking more fluid but it's not leaking out anywhere, it's storing it somewhere. The most likely place is inside the transfer case, where some older-design cases leak internally. Read through another current thread on "4matic".

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ASE Master Tech
Quality Enterprises
Mercedes Svc. & Restoration
Sheridan, IN
317.769.3536

I can't find any external evidence of fluid leak, but must confess to not once checking the fluid level in the hydraulic reservoir in the past 12 years. It was app. 1/2 litre low, and after filling it, the level has remained constant for 3 days and 50 miles or so. It would appear to me that if the fluid were topped up any sensors would respond to that by returning to normal operation. If there is an internal leak, it is a very slow one. The 4matic light still stays on and 4matic won't engage. I'm assuming it is OK to drive the car as long as underhood function valve is in the "test" position? Thanks

Try this.put the 4 matic switch to run and disconnect the battery for several minutes.this will reboot the 4 matic cpu and clear any error codes.drive it around for awhile and let us know what happens

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michael cole 1980 300SD gone now but not forgotten,87tdt,90 300te 4matic 95 e320 wagon

I tried your suggestion about rebooting the cpu, still have a light on the dash and no 4 wheel drive engagement. The snow is melting fast and that will give me some time to fix this before next winter. Thanks, Ron Jolliffe

Does the 4 matic light blink out an error code when you start the car?count the flashes it may give you a hint on whats wrong

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michael cole 1980 300SD gone now but not forgotten,87tdt,90 300te 4matic 95 e320 wagon