Attempting to repair servo ABS unit

After my previous "Servo ABS Unit parts?" I said I would start a new thread with my attempt to repair it so here it is.

I am not an expert in any of this - just thought trying to repair my unit will only cost me some time (although I might learn something on the way) and want to try before I go down the servosectomy route. None of it might work and I might end up with a servosectomy in the end but if I don't try I won't know. With this in mind any comments or suggestions will be more than welcomed - especially if you think I'm doing something wrong or being stupid with something

As in my previous thread I removed the ABS Unit and took it apart. I found the pressure switches on the rear of the unit badly gummed up and one of the switches broke when I tried to clean it:



So the very nice Dr Farkoff sent me a couple of used ABS units:



The one on the left looked identical to my R1200GSA one and the one on the right is off a R1150 I think but although it looks different a lot of the parts are the same.

I pulled the two sent to me apart and the pressure switches looked identical on all 3 units but the cleanest ones were on the R1200 unit sent by Dr Farkoff so will use this on mine.

Whilst pulling the units apart I noticed a lot of gunge and dirt inside them all but the pressure switches on mine were definitely the grottiest looking. I then decided it would do no harm to clean my unit out thoroughly so I pulled it apart as well:

I tested what I could as follows:

Servo motors - hooked up a 12V battery to each motor in turn and all seem to run smoothly from the 2 R1200 units but the ones from the R1150 units do nothing.

ABS Solenoids - I just measured the resistance of the coil - I got 1.5 Ohms on all 6 solenoids so I am assuming they are all good:



Float switches - on the R1200 units the plastic housing on top contains two float switches for the brake fluid level so using a meter I checked that they worked which they did on both units:



Filters - there are a couple of filters at the bottom of where two of the brake pipes are connected - I removed these and cleaned out the filters (one of mine was definitely grubby):



Pipes - there are a couple of little pipes that come out when you pull the unit apart and there was some crud in both of mine so gave them a good clean out:



At this point as I kept on spotting various bit crud and syrupy looking fluid in various corners of the unit so decided to take apart completely and clean everything:



For cleaning I used isoprop and wiped everything down to hopefully leave no traces of anything in the corners. I've put the bits in a warm dry room before putting it all back together at the weekend. All the mechanical components and o-rings etc. inside all of the units all seem to be in good condition so I am hoping it is just the dirt and gunge that builds up that kills these units (and the broken pressure switch in my units case) and it might all work again soon.

Good luck . I got lucky a few times, first cleaning out the filters and the units worked again ( posted it on ukgser hoping I'd found the fix for servo/abs units), second was the pressure valves, again I got lucky on the first few. After the initial success I then had no more luck . Hope you have better luck. I've about 30 modulators kicking around in my garage so I've no shortage of parts ..

Very interesting Pal keep it coming

Yes I think I've read all Steptoes posts on the subject - that's where I got the info for cleaning out the filters from.

The stuff around my pressure switch looked to me almost as if there was some corrosion in there as well and I figured that could cause it to give inaccurate feedback to the electronics - fits with what the GS-911 said about high pressure in the front brake circuit. I also spotted what looked like a hairline crack in mine and when I started to clean it that's when it broke - I wasn't using any force and when I cleaned the pressure switches on the other units I definitely scrubbed a little harder with my toothbrush and nothing broke in them. So who knows maybe it is just the pressure switch in mine.

On the next steps I have seen the posts and "how too's" for bleeding the servo assisted brake system but I will be starting with an empty unit (no brake fluid in mine now!) so if anyone has any tips or hints for this please let me know

Didn't get as much time this weekend as I'd hoped - had to go to work

Anyway got the unit back together again today:


I wiped each component as I put it back in and put a smear of new brake fluid around each piece and used a syringe to put some new brake fluid into some of the tighter corners and spaces to hopefully give me a headstart when it comes to bleeding the whole system through.

I put it back in the bike and connected all the pipework back up:


It was a bit fidly wiggling it about to get it back in but it does eventually go.

I used a syringe to fill the unit up with new brake fluid. At this point I decided to leave everything to settle to hopefully allow some of the air bubbles to work their way out before flushing and bleeding the whole system (I was going to use this procedure: http://www.ukgser.com/technical/nick/Brake bleeding (All BMW EVO systems, '04-'07).pdf found on this site to do this) and since it seems a long and time consuming procedure I want to start this in the morning when I know for sure I have the whole day clear.

A couple of pointers during disassembly / reassembly:

The security bolts (5 pointed torx security thingies) were a bit on the soft side - managed to chew the heads on a couple of them - the R1150 unit has some 3 point things (I think they are called tri-wings) which were even worse.

The top plastic part and pressure switches on my R1200 unit seemed to be partially sealed with some sort of instant gasket as well as a rubber seal. The R1200 unit from Dr Farkoff seemed to just use a rubber seal. This is strange because I've had my GS since new and I know nobody has ever had the ABS unit apart - does this mean some units have been opened and resealed before leaving the factory . Anyway, I decided not to use any instant gasket stuff putting it back together - I used the best looking rubber seals from the 3 units - I'll find out soon enough if nothing leaks when in use.

To get the parts out that the pipes are connected too I couldn't get a 15mm spanner in to them (at least until I had taken the plastic top with the level floats in them off) - so I modified a 15mm socket by cutting of 4 of the six flats off:


When removing the solenoids I found a slight twisting and pulling action with fingers only was the best way to get them out. If they come out with o-ring attached (some did and some didn't) there is a metal ring below. If this metal ring is lifted out there is a small spring / valve that pops out of an small oil channel at right angles to the ring - awkward to get back in but also worth noting as it's a narrow channel and probably worth a clean out.

For more pictures that I took whilst pulling the units apart follow this link: https://postimg.org/gallery/30mpeyo0a/

Hunda67 said:

Didn't get as much time this weekend as I'd hoped - had to go to work

Anyway got the unit back together again today:


I wiped each component as I put it back in and put a smear of new brake fluid around each piece and used a syringe to put some new brake fluid into some of the tighter corners and spaces to hopefully give me a headstart when it comes to bleeding the whole system through.

I put it back in the bike and connected all the pipework back up:


It was a bit fidly wiggling it about to get it back in but it does eventually go.

I used a syringe to fill the unit up with new brake fluid. At this point I decided to leave everything to settle to hopefully allow some of the air bubbles to work their way out before flushing and bleeding the whole system (I was going to use this procedure: http://www.ukgser.com/technical/nick/Brake bleeding (All BMW EVO systems, '04-'07).pdf found on this site to do this) and since it seems a long and time consuming procedure I want to start this in the morning when I know for sure I have the whole day clear.

A couple of pointers during disassembly / reassembly:

The security bolts (5 pointed torx security thingies) were a bit on the soft side - managed to chew the heads on a couple of them - the R1150 unit has some 3 point things (I think they are called tri-wings) which were even worse.

The top plastic part and pressure switches on my R1200 unit seemed to be partially sealed with some sort of instant gasket as well as a rubber seal. The R1200 unit from Dr Farkoff seemed to just use a rubber seal. This is strange because I've had my GS since new and I know nobody has ever had the ABS unit apart - does this mean some units have been opened and resealed before leaving the factory . Anyway, I decided not to use any instant gasket stuff putting it back together - I used the best looking rubber seals from the 3 units - I'll find out soon enough if nothing leaks when in use.

To get the parts out that the pipes are connected too I couldn't get a 15mm spanner in to them (at least until I had taken the plastic top with the level floats in them off) - so I modified a 15mm socket by cutting of 4 of the six flats off:


When removing the solenoids I found a slight twisting and pulling action with fingers only was the best way to get them out. If they come out with o-ring attached (some did and some didn't) there is a metal ring below. If this metal ring is lifted out there is a small spring / valve that pops out of an small oil channel at right angles to the ring - awkward to get back in but also worth noting as it's a narrow channel and probably worth a clean out.

For more pictures that I took whilst pulling the units apart follow this link: https://postimg.org/gallery/30mpeyo0a/

Click to expand...

Good stuff

To anyone reading this - whatever you do DONT use anything like cotton buds for cleaning into tight corners. They WILL leave fibres behind that will mess up all your good work. Talk to a clock or watch repairer and use whatever suggest for the awkward bits.

Bendy toy said:

To anyone reading this - whatever you do DONT use anything like cotton buds for cleaning into tight corners. They WILL leave fibres behind that will mess up all your good work. Talk to a clock or watch repairer and use whatever suggest for the awkward bits.

Click to expand...

Good advice this. Have a look on ebay for foam tipped cleaning swabs.

Actualy that is a good point - I had some cotton buds I used at the start but saw small fibres being left behind so decided not to poke them into any narrow channels.

I found the best way was a soft toothbrush with lots of isoprop to wash the bits out - my theory with the isoprop is it will evaporate away quite nicely especially if left for a few days. I probably used the best part of a litre of the stuff.

I guess an ultrasonic cleaning tank would have to be large & therefore costly.


Sent somehow.

I think an ultrasonic cleaning tank would have been the ideal solution - unfortunately don't know anyone with one though.

I have a little US tank ok for carb parts but no way would a brake servo fit in.


Sent somehow.

Decided to make a start this afternoon as I got home early today with the brake bleeding etc. I haven't bled in brakes in many years (and anything I did in the past certainly didn't have servos and ABS) so any intervention here from anyone is fine

As mentioned above I am following this procedure: http://www.ukgser.com/technical/nick...704-%2707).pdf

I made the filler funnel with a cheap plastic funnel and some self amalgamating tape:



The tape is soft enough to screw the funnel into the ABS unit fillers without any fluid leak.

I also made some spacers out of flat 3mm aluminium bar as suggested in the procedure:



So first part of the procedure is to bleed the wheel circuits i.e. from the ABS unit to the calipers. First problem encountered was I just could not get the spacers in with the brake pads - I pushed the pistons as far back as they could go and it was just not going to happen. Maybe it is because my brake pads are less than 1000 miles old - I am assuming the spacers are there so fluid is not overfilled when new brake pads are fitted further down the line - if this all works out I intend to replace the brake fluid on a yearly basis and my pads are good enough till at least then with the mileage I have done recently

Anyway decided to proceed without fitting the spacers and the procedure seemed to work fine - servo motors were pumping new fluid from funnel and out of each caliper in turn - I flushed through until air bubbles stopped coming and then kept going to ensure thorough flush through with new fluid.

At this point my brake leavers are still very floppy but I'm guessing this is because control circuits will have lots of air in them still and that will sort itself out after bleeding and flushing through the control circuits but that part is for the weekend now.

Have just left the bike for now with the battery on charge (use of servo motors alot this afternoon) and will see if anyone comments on anything I have done so far..........

Sounds all good so far think it's good to let fluid stand overnight it's surprising how much air works it's way out.

I'd probably have flushed from the ABS unit side of the pipework (ABS Unit not fitted) to the callipers until I had clean fresh fluid I'd then have refitted the ABS unit and done the control circuit with the ignition off first and then backflushed the calliper to the ABS Units with a clean syringe fluid and hose Let it sit 24 hours and then check the results and prepare to bleed the circuits

If your way works? Then, thats fine, Whatever works is the motto

Thanks guys.

DrFarkoff - I never thought of that but it does actually sound like a good idea.

The whole thing is a learning curve for me and who knows if it works in the end

In most cases it's best to tie the brake lever back/down and leave overnight. This allows fine bubbles to escape. Always set the handlebar so there is a continuous up-slope from hose through master cylinder to reservoir. At the rear brake, just wedge the lever down.

Next step now:

Decided to do the control circuit bleeding yesterday. Started with the front brakes by following the procedure and all seemed to go fine. I used a syringe to remove the old brake fluid from the handlebar resevoir and replaced with new fluid. It was easy enough to do by myself - right hand doing brake lever and left hand operating bleed nipples on ABS unit (bleeding wheel circuits was also doable by myself as it seems you are using the servo motors to pump the fluid through so I could reach brake lever with one hand whilst kneeling by caliper to operate the bleed nipple). It took ages before the air stopped coming through but I guess that's because the whole system was basically starting empty - I also found with the 4 short nipples on the ABS unit it was easy to knock the tube away from the nipple with the spanner:



The trick was to make sure the tube is nicely routed before starting - I just used some cable ties to hold in place. However, I did manage to knock the tube off at one point and the spilt fluid runs down the rear side of the ABS unit in appeared below in the bash plate and on the centre stand Anyway completed the bleeding of the control circuits, closed everything up and wheeled the bike outside for a quick wash to remove the spilt brake fluid. Was dry and windy so let the wind dry out the water from all the awkward crevises.

Once the bike was dry I put it back in the shed and decided to follow the advice above to let any remaining air work it's way out of the system overnight.

Today I repeated the entire bleeding procedure (wheel and control circuits) - a few small air bubbles came from the control circuits still but I kept going until I was certain there were none - I've used a total of 1.5l of new brake fluid - but I figure brake fluid is cheap and I'm now certain I have no air and completely new brake fluid throughout the system.

At this point brake levers felt good. With ignition on the correct startup procedure with the buzz from the ABS unit and the "brake failure" warning light coming on and flashing slowly - before all this started the "brake failure" warning light flashed fast at least 50% of the time when turning on the ignition so that's the first good sign. Second good sign was before all this started I would apply front brake and sometimes servo would just keep whining away when lever released - this is also not happening now.

So feeling hopeful I sat the fuel tank and seat back in place and took the bike for a tentative spin up the road. First thing noted was that "brake failure" warning light went out within 10 feet of the bike starting to move - in the last few years when the system was working this had taken up to 100 yards plus. Run up and down the road half a dozen times and all was working normally. Switched off ignition a few times and everything normal with the warning light always going out within 10 feet of moving

Next thing I'll do is give everything a check over to make sure no leaks from the system anywhere and try to get hold of a GS-911 for Brake Pressure Hold test - I don't know if this is essential to do but I think it's probably very wise after having the whole thing to bits.

Happy with the results so far but I won't hold my breath yet

Nice one ...

Are you going to start repairing any more?


Mart

Well done that man!
Satisfying isn't it?
Never do understand the rip it all out because I don't understand it mentally.