W124 300E 4matic 1989

[alien300e]

I have a 300E 4matic running on LPG

Can anyone explain how the 4matic works as mine is now playing up i think.
At any speed the warning triangle comes on in the speedo and the whole drivetrain seems to vibrate, whilst the car seems to fight left to right. However the minute you lightly touch the brake pedal (not even applying brakes) light goes out everything smooth. Let go of brake, vibration again.
It has always had the triangle come on and has always gone out with the brake pedal. The vibration is more recent and definately getting worse.
Also has the usual ABS fault which is still intermittent but more regular now but i know this will be a wheel sensor. Are these 2 faults related?
Car has done 125K and i don't want to have to get rid of it.

 

[Blakey]

To me your problems sound totally abs related, and nothing to do with the 4matic gearbox.

 

[alien300e]

Thanks for the reply, i'm inclined to agree so i'll start off by looking into the abs first. I'll let you know.

 

[GEORGEROV]

Hi Alien, I ran a high mileage 4-matic for a few years and had the problems you mention at one time or another. The front wheel sensors are used by both abs and 4-matic systems. Wheel sensors go high resistance initially causing a pulsing of the brake pedal just when coming to a stop. The abs light wont come on when this happens. Eventually when a sensor does go open circuit then the abs light will stay on continually. As regards the 4-matic system then a lack of fluid will cause the system to lock up the differential between front and rear axles.(Diff is locked by default and fluid pressure overcomes the lock under normal running). Hydraulic pressure also controls rear axle differential , front wheel engagement and the above mentioned transaxle. Apart from these components developing leaks in the associated steel tubing, the transfer case itself WILL require replacement at some stage. The seal in the case separating the hydraulic fluid from the transmission oil breaks down and contamination of the oil causes brass release bearings for the multi clutches to wear out. A great system when its working and far superior to the Volvo cross country I had after it but a nightmare to repair on an old car with the myriad of steel pipes, valves etc.

 

[alien300e]

Thanks Georgerov, the pulsating of the brake pedal is spot on, i've had that since i bought the car but even that is now more severe. The abs light will still sometimes stay off for 20 minutes of a journey and about a month ago it was ok for almost a week, now however almost straight away nearly all of the time, do you think this is likely to be intermittent connection or do i need to replace them? Thanks again

 

[GEORGEROV]

The pulsating pedal was cured after I cleaned the reluctor rings of crud after dismantling the hubs but my 500 had the same problem with a duff sensor. So the problem I think will be one or the other of the above. You can measure the resistance of the sensors at the wiring connectors near the strut towers. (co-axial plug connectors) and these should be between 1 and 2 kohms if memory serves.