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| bimmerc Veteran Date registered: Jun 2009 Location: Alta, Norway Vehicle(s): 1992 300GE swb Portals, 85 300GD STT Cab swb Posts: 102  | ABS - changing hydraulic unit My 1992 300GE needs a new ABS hydraulic unit as all 4 solenoid valves are stuck. The ABS has not been working the last 6 years according to the last two previous owners. I have tried forcing them to open by knocking on them and applying 12V directly to the solenoid but to no avail. Now I have found a used module on eBay. My concern is if there are specific procedures to follow when replacing unit with regard to getting the air out of the system. The ABS system, as I understand it, is separated from the regular brake system until you switch it ON (simplified). That means the circuit is not triggered while you fill brake fluid and get air out of the main system. My plan is to apply pressure to the brake pedal and trigger the four solenoid valves one by one manually by applying 12 volts directly to the solenoids. This will let fluid into the valves? Or should I assume that there is fluid in the valves given it is a used unit? I will remove plugs and relays from the ABS unit while doing this to isolate the solenoid valves from the circuit. Battery and ABS ecu will also be disconnected. Am I on the right track or missing out on something?  I am an electronics engineer and have played with a working ABS hydraulic unit from a w124 sedan (3 channel vs w463 4 channel). And of course watching endless YouTube videos to get an understanding of how it works. BUT I have not tested my knowledge on anyone who knows the system. I only think I know! And that, I know, is dangerous.  | |
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| nadd Expert Date registered: Apr 2006 Location: UAE, Dubai Vehicle(s): G500 2016 LHD, numerous Chevys Posts: 1285  | ||
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| bimmerc Veteran Date registered: Jun 2009 Location: Alta, Norway Vehicle(s): 1992 300GE swb Portals, 85 300GD STT Cab swb Posts: 102 | RE: ABS - changing hydraulic unit My 1992 has a 4 channel system. the 3 channel system was introduced in 1993 on the 463. Sorry for not making the obvious clear, mate! I forgot to say that I will apply 12 volts to the pump when I activate the solenoid valves.  | |
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| bimmerc Veteran Date registered: Jun 2009 Location: Alta, Norway Vehicle(s): 1992 300GE swb Portals, 85 300GD STT Cab swb Posts: 102 | ABS - Hydraulic valves testing While waiting for the replacement unit I have played with the one not working. The valves are badly stuck and even applying 24+ volts to the solenoids could not persuade valves to move. As far as procedure for bleeding the system after replacing unit I get different suggestions. And that is exactly what it is: Suggestions. I know that the worst thing that can happen is that I do not get the ABS back but the brakes will work perfectly after bleeding the system the normal way. So unless anyone comes up with something different I will just replace the unit after first checking that solenoids and valves are working and take the next steps from there. The only thing I cannot test properly is the ECU (Electronic Control Unit) but I have been assured that I receive a working unit with the Hydraulic module. Both comes from same car. Wish me luck! | |
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| nadd Expert Date registered: Apr 2006 Location: UAE, Dubai Vehicle(s): G500 2016 LHD, numerous Chevys Posts: 1285 | RE: ABS - changing hydraulic unit Here's my first attempt at attaching instructions for bleeding from WIS. I believe 4 channel ABS is more advanced than 3 channel, so why would MB go backwards with time! Edited by nadd 8/29/2014 12:57 PM Attachments ----------------  2014-8 Bleed brake system.pdf (542KB - 9 downloads) 2014-8 Carrying out bleeding operation.pdf (355KB - 8 downloads) 2014-8 Remove Install ABSunit.pdf (537KB - 8 downloads) | |
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| AlanMcR Expert Date registered: Apr 2006 Location: US, CA, Los Altos Vehicle(s): G300DT E300DT 230SL Posts: 3500  | ||
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| bimmerc Veteran Date registered: Jun 2009 Location: Alta, Norway Vehicle(s): 1992 300GE swb Portals, 85 300GD STT Cab swb Posts: 102 | ||
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| Gilamonster Veteran Date registered: Sep 2013 Location: New Mexico Vehicle(s): G #1 (mix of a 460, 461 & 463), #2 is a 2000 G500 Posts: 151 | ||
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| bimmerc Veteran Date registered: Jun 2009 Location: Alta, Norway Vehicle(s): 1992 300GE swb Portals, 85 300GD STT Cab swb Posts: 102 | ||
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| louwdj Veteran Date registered: Feb 2007 Location: Johannesburg South Africa Vehicle(s): 89 W460 230GE 5 door; 82 W123 230e; 99 W210 E240 Posts: 139 | ||
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