Dear ShopForum, I have a challenging problem to solve. I recently purchased a 1990 300TE 4matic wagon. The yellow triangle was on all the time and it turns out that the tandem pumpe seals were gone and also the transfer case was full of Hydrolic fluids and power steering pump fluids (seals gone there also) I had the pumpe and the transfer case replaced (parts by MB rebuilds inc. Canada) and the problem is still there. The mechanic has checked and cleaned all the relevent sensors, checked the hydrolic actuator in the rear of the vehicle (all work and clean). This would not be so bad except that the front differntial remain locked so tight turns are not good. Plus I do not believe the system is designed to run in 4X4 full time. The 4matic ECU gives a code 1 so we do not suspect a bad ECU. These mechanics have a good reputation and seem to be doing the right things, but we are all stuck now at what to do next. Any suggestions would be appreciated. Regards, Chesterloosee

You might want to consider replacing the control valve assembly at the rear of the vehicle. It is responsible for feedback to the
4-matic ECU (pressure sensing) as well as controlling the drums inside the transfer case and the ASD (locking diff). The nitrogen cell that is attached to it may also be ruptured.

That was the most expensive 4-wheel drive system ever engineered on the planet.

I wonder if your valve assembly is the same unit as the Hydroclic actuator I was mentioning? Perhaps I am using the worng terminology. The unit was taken off and tested with a new one. No change. We are testing the pressure out of the tandem pumpe to make sure the rebuild worked.

I agree with your comment on the cost of the 4matics...

The garage cannot spend anymore money on R&D for this. So, they disconected the relay to the valve actuator in the rear. This diables the 4matic but not the auto leveling. They suspect either a bad ABS computer or a bad 4 matic computer. Neither show fault codes. I wonder if these computers can be found used?

hi ive got a 90 4matic te.my transfer case is still good so i feel very lucky.i usually shut it down during the spring summer fall by switching the test lever to "test" for a moment with the engine running and then back to "normal".this generates a fault code in the 4matic "brain and stops the hydraulic valve from actuating the transfer case.at the same time it allows the self levelling to continue working.as long as you dont disconnect the battery and reset the 4matic "brain it will continue to operate in this fault mode.i assume the tech has drained the xfer case and replaced the atf.if the front diff is locked it may indicate a mechanical fault within the case caused by the combo of hydraulic/atf.just driving with new fluid may clean up the xfer case internals and then again you may be faced with replacement.its alway good preventative maintenance to check the hydraulic fluid level on these cars everytime the hood is open.as well change xfer case atf every 12k miles.there is a very good discussion group called 4maniacs offering lots of moral support.

As ytou can see form the above, the transfer case was replaced and it still will not disengage from 4matic mode. We figure is is a faulty ABS or 4matic ECU.

Thanks for showing interest.

Are the lines to the tranfer case crossed? I am not certain if you can do that at the case but you might want to double check the inlets and outlets at the control valve assembly. Yes, that is the one in the rear with the nitrogen cell affixed to it. Two switches and one sensor are also attached to that valve assembly.

If you need some more info..........let me know.

I spent some time with that system.................your reman case could also be the problem but lets focus on the basics.

Checked the lines. All going in the right direction and all have good hydrolic pressure.

Have you attempted to check the control signals at the valve assembly? I would back-probe the switches to see if they are getting a signal to be "on." If so please let me know what circuit numbers and I will see what I can come up with.

The diff is programmed to be locked up to 12mph or so, this signal should be present on takeoff than disappear at or near this speed.

Not to second guess the diagnosis but are they certain the front axle is in operation and causing this complaint?

Yes, the diff is locked at all times unless I touch the brakes. Then it disengages. They have stopped work on it, and I am not mechanical enough to perform the check by my self. The ECU for the 4matic shows a code of 1. That was it. The valve assembly unit was replace temporarily with a new one (borrowed) and nothing changes in the behavior of the 4matic.

Try a new brake lamp switch. If I recall correctly it is a dual type switch, a normally closed and a normally open circuit.


One other note, the diff should not be locked after 12mph(approx) and that may be why you are experiencing this lurching or locking up feeling in turns.

I'll dig out my notes and get back to you.

Just an odd thought, is your speedometer working?

yes it is.

This is the best info i have found on the 4matic function.

http://www.frejvall.com/4matic



Pelle

300E 4M -89 5speed

Thanks, already been in touch with Per.