My 1990 - 300 TE 4MATIC recently started running low on power steering fluid. When I filled it up, it just overflows into and out of the 4Matic/ALS reservoir and then the power steering reservoir becomes low again. The system doesn't seem to have any leaks other than above mentioned reservoir overflow. 4Matic dummy light was on for awhile before problem appeared but went out when I added MB hydraulic fluid. I purchased a factory service manual but can't find any reference or solution to the problem.