hi there im new to this forum group, and i have a 1990 300 te 4matic and all is somewhat smooth , with her .
Ive browsed most sites and almost all of my symptoms that i have found about my car they are pretty well even across the board for my estate wagon,ha . german qaulity ,

i have found no question like the one i have posted in a few other forums and i have yet to be responded to , so here it is;

i have read in my manual that there is a "test valve" in the engine compartment , which, activates/deactivates the hydraulic funtion of the transfer case , also disabling the load level system hydraulics,
in my query i pose this , in hopes that i can prolong the transfer case 's lifespan(it seems to funtion although i have to bleed residual air in the valve body, to correrct the 4 matic lght) is any one in this forum aware of this valve and any possible damage that may ensue,from prolonged driving in this test mode?
i will have many ohter posts like this one i have a vague idea and i am looking for second opinions sorry for the size of this post

As far as I can remember, the valve you mentioned should only be used only for stationary tests and/or emergency runs. Otherwise, you will certainly damage the 4matic gear under regular driving with the test valve activated.

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A. Rosich
CL 500, 1998
S 500 L, 1998
E 320 T, 1995 [Sadly sold ]

i have discussed this issue with my mb tech here and with what knowledge he does have for this year of vehicle he thinks that no damage can be done as the valve is to allow hydraulic pressure from power steering pump to be applied to the visous coupling in the transfer case. the gear inside the transfer case has its own fluid and is a sealed unit , so his theory is that all it will disable is the pressure activation ,and the load levellling feature of the suspension.

you opinion is the first reply to any postings i have made on this subject and i will hopefully get responses , in accordance to this subject that will be as helpful, any post will be helpfull as long as they are on this subject and informed

may i ask where you got your info ?

since the valve will disable function of the rear suspension i dont recommend leaving it in the test position for long.the rear springs were designed to work in conjunction with the hydraulic shocks for load levelling and ride control.

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

As im not in any way shape or form an educated person about such issues , i post these queries to hopefully shed light on my ideas and situations.

that said; it is my understanding that the only time when the load leveling system is required ie in use is when you vehicle load has been increased thus lowering you ride height, a lever on rear axle open passages to rear SHOCK and thus adjusating ride heght to normmal range Automatically , some cars i believe have a manual adjustment beside the headlight switch.

Through reading the owners manual and my discussion with various tech i have come to the pre posted conclusion and i am hoping to clarify hopefully for all those who have owned , do own , and want to own a 4 matic.

again i will state this is in hopes of prolonging transfer case lifespan on an old vehicle, suspension characteristics of this vehicle are still acceptable and ride is still nice with valve on , yet i am still hoping i can get someone who would have connections to hopefully track down the truth , will be buying a mb manual soon .

if your primary concern is prolonging the transfer case try this.with the engine running turn the switch to test.then after a few moments back to run.this will generate a fault code in the 4 matic computer effectively shutting down the 4 matic operation.you can confirm this with the 4matic light in the instrument console being lit.when you wish to resume 4 matic operation simply disconnect the battery for a few minutes.this will reset the 4 matic computer

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

thats pretty clever...

thanks.ive truly enjoyed the process of discovery that comes with ownership of this truly misunderstood vehicle

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

The only experience I have contact here in the tropics has been with an 300 E 4matic the previous owner of the local M.B. dealer brought for himself.

From the day one the car started giving all kinds of problems with the 4matic system. After one year the car was returned to Germany. I remember that the techs at the dealer talked about this test valve and heard the comment that it should only be used for tests and maintenance. The owner wanted to disconnect the system, but it was not as simple.

The other option recommended by Michael Cole seems more adequate, although I remember also comments about the planetary gears suffering from premature failure if the 4matic system on W124s was used disconnected or with a reported failure by the computer.

Now, having owned several M.B. wagons I can tell you it is not advisable nor safe to drive with the rear self levelling hydraulic system disconnected.

Yes, the rear self levelling suspension does regulate the height of your rear axle upon the current load on the vehicle. Although, it doesn't mean the system only works when the car is loaded. The system works permanently and is what provides cushioning and control for regular driving. If you turn off the system, you could still drive the wagon, but it will become extremely hard at the rear providing a very umconfortable ride. Also, it will generate premature ageing on all suspension components.

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A. Rosich
CL 500, 1998
S 500 L, 1998
E 320 T, 1995 [Sadly sold ]

In my travells i have come across the hydraulic schematics of this car and unfortunately i cannot post it yet , if any one has more info on this car , i am about to purchase the 124 cd rom , i am hoping it is very specific on this model , if it is not i will be in the hunt for true info on this car , i have found that these cars have many "model specific" parts, and of course that is added to the cost of parts ,

This test valve post is one that i hope we can resolve about damage to the suspension, transfer case.

i can apply test valve and light comes on and then i can turn off and light will come off , i have also changed all the fluid on this car except front diff , and trasnfer case indeed is a sealed gear box and a sealed hydraulic clutch,(viscous coupling), if any of the 2 fluid mix , Ie internal leak means rebuild on tc ($3000) . indicator is you check fluid at fill of transfer case and if fluid comes out (excess of 2to 3 tbs) is a true indication.

my tech here an ajax inform me that dextron 3 is fine on tc , zhm fluid for hydraulics and 80 90 hypoid is good for front/ rear diff. i have mentioned a few item on this post previously , i am still looking to answer if damage will be done to transfer case , hydraulic suspension aside the rwd mode is also i believe a locked hydraulic system , which i believe means what pressure is in the system stays in the system . as proof there is always fluid in the shock and as the they are in line with accumulators which are gas filled, that is where you get the "ride" and feel .
I am getting this information from a few mercedes mechanics in the area , of course that is through looking at the diagram and through working on this system , i am most likely incorrect is some of these statements, but i will never find out unless i make these statements , and someone knows better.

thanks for the info.

p.s. 3 of the gentlemen i talked to have thier own shops and one is the shop foreman at mb durham,

if your xfer case is leaking i recommend a switch to mobil1 atf thru out the whole hydraulic system.myself and others have done this with no apparent downside.besides the mercedes fluid is outrageous pricewise

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

if your 4matic light refuses to stay on drive the car a short distance.then flip the lever back

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

i am in the process of changing all the fluid , and i am down to the front diff , went to dealer to get pan gasket as there is no drain , and they couldnt find the part i was looking for they ordered me the oil pan gasket,
I go pickup the parts and i TOLD them it was wrong and ! guy walked away from me ( the guy who ordered the part and i had to talk to another guy , wtf , ) i go home with wrong part in hand and verify( wrong!!!!part?)
they couldnt even find the front diff cover , they do show me that the front diff is incorporated into the block, and is actually part of the "oil pan" just a little FYI for 4 matic owners out there .

did i read that right ???

atf , i had previuosly put power steering fluid and i was tolf of possible internal seal damage , but this is certainly new news to me?

any one else hear of this???

atf is a hydraulic fluid.in fact the spec sheets for atf will tell you that.

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