I think the 190 will be 3 channel ABS. This means that separate lines go to three areas, left and right front and both rear.

If that is the case the ABS is not the reason why one caliper won't bleed. If I am wrong and the system is 4 channel it will have 4 lines out. One to each wheel and if this is the case there is a good chance you do have an ABS actuator problem.

I have had three in twenty years but the last two were in the last year. Two have been BMWs and one was an Audi. Same type Bosch ABS as MB has.

During activation of ABS the line is blocked in one stage and hooked to the pump in the other activated stage. Anywhere in those two positions fluid will not pass to the caliper. The situation can be confirmed by activating the solenoids and listening for them to work. In the ones we have had three could be heard and the one not flowing couldn't.

We originally jumped the solenoids to see if we could unstick them. Didn't happen but it did show tyhe problem when we found we could hear the good circuits applying and the bad one, not.

We fixed all of them with used actuators as they are about bulletproof. Just so I would be prepared for my first MB I bought one like on your car for $50 on ebay the other day. They are over 2 grand new. I have never paid more than $300 for the used ones though. Junkyards have no use for them, there is no market.

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Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician