The flushing procedure for the 91 M103 calls for 2 flushes with deoiler and 3 flushes with citric acid. I believe you can use diluted dishwashing soap as a deoiler. Citric acid is supposed to be used in a 100g/l solution. If you email me directly, I'll check the manual to be absolutely sure.
Flush with the engine thermstat out and the ACC set to defrost. Run the engine to 80C then allow it to cool to 50C before draining. Run straight water as a rinse between flushes.
86 300SDL (due soon)
81 300SD (for sale cheap)