Very common for air pocket in the VERY back section of reservoir. Try OVERFILLING the reservoir & allow time for it to fill that section of reservoir. This happens to even very good dealership techs. The line closest to the booster is for the front. NEVER push old fluid back into system on ABS cars! Always open bleeder w/pushing pistons back into caliper. When you bleed system do you get good fluid flow??

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MERCEDES Benz Master Guild Technician (6 TIMES)
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