May want to check the ABS pump relays.

Here's a good tutorial

https://www.pelicanparts.com/techarticles/Mercedes-W124/65-BRAKES-ABS_Relay_and_Pump_Replacement/65-BRAKES-ABS_Relay_and_Pump_Replacement.htm

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Stable Mates:
1987 300TD 310K mi (Hans)
2008 Jeep Grand Cherokee OM642 165k mi (Benzrokee)