Attempting to repair servo ABS unit

As I say not holding my breath yet

Don't plan to repair any more - I am not a brake expert or mechanic of any sort. Just trying to keep my bike working as best I can - if it packs up again I will probably just do a servosectomy but just wanted to see if I could repair it before going that route.

I think the main problem with mine (broken pressure switch aside) was the amount of dirt and crap inside the unit - I think cleaning it thoroughly was the main fix and I think anyone could do that if they take their time and are careful - after all I managed it

If, however, the broken pressure switch is common then getting the parts is the problem - I couldn't have done anything about this without DrFarkoff sending me a couple of defunct units - i.e. I could not have got this far without his generosity

And yes it has been very satisfying doing it so far - just enjoying a celebratory Guiness right now

Extremely well done. Top Job

I would get that brake fluid properly cleaned off the engine.

I have ordinary ABS but one of my front steering struts was a horrible mess of corrosion and the engine top paint had totally flaked off.
I suspect brake fluid damage back in the dim & distant past.


Sent somehow.

Great job, you must be really pleased with your work.
Bloody brake fluid gets everywhere especially when you have so much bleeding to do. The pipes always fall off when you least expect it.
If only you had longer nipples...

Brilliant job well done !!

Thanks everyone - and yes longer nipples would be good

Tried it again last night and was still working and no sign of any fluid leaks, so I'm still happy

However, have decided to splash out on GS-911 as to have confidence in it all I think I need to see a succesful pressure test result It's bad enough when you get unexpected residual braking kicking in when you don't notice the warning light comes on and I don't fancy no brakes (if that's possible) without warning.

So I won't call it fixed until I get a successful test on the GS-911.

Now for the next jobs that need to be done:

DWALO! fault is coming up.
Gear position indicator talks bollocks about half the time.
Rest of bike needs a full service.
And while I'm at it I've always thought the bike would look good with matt black plastics instead of white so maybe will get the paint out

Paint tends to be permanent.
You could wrap it then rewrap when you get bored.
I fancy doing the matt black plastic parts in brushed aluminium look. They are small enough for a rank amateur to do a stunning job or mess it up entirely with no lasting harm done.


Sent somehow.

Treated myself to a GS-911 It arrived yesterday so out to have a play with it today. Once all setup and connected to the bike I looked at the ABS unit errors:

25193: Brake fluid level to low
The fault is not present now.

25074: Internal control module error - Analog value of front control pressure sensor
The fault is not present now.

24957: Internal control module error - analog value of rear control pressure sensor
The fault is not present now.

24971: Pressure in front wheel circuit to high
The fault is not present now.

So these are the historical errors before I did anything and all were not present now so a good start

I then ran the "Bleed Tests", "Sensor Drift Test" and "Brake Switch Adjustment Tests" and all passed.

The ABS Status page looked like this:



Just as an aside looking at the ABS Control Times - does that mean in the 10 and a half years I've owned the bike the ABS has never kicked in on the front wheel

I hope these pressure figures look good to anyone with more knowledge than I have but I'm assuming that because the GS-911 says they are OK then they are OK .

Anyway, I cleared all the errors and took the bike for a spin round the block (the block is a 10 mile trip on single track roads around here). I made sure I used the brakes a lot. When I got back I plugged it in to the GS-911 to see if any errors had come back and there were none. I also ran the tests again and all still passed. So now I am happy with the result of all this

So onto the next jobs listed above plus also the rear subframe has started to rust in places:



but it all seems to be at rear of rear subframe if you see what I mean (no rust from battery box forward for some reason). I think I will remove all plastic and bits off the back of the bike and try to paint the rusty bits - don't really want to remove the frame as along with removing swingarm etc. it means removing some brake lines and I don't want to do that now that the brakes are working . If anyone has any tips for paint etc. to use on rear subframe they will be greatly appreciated. Anyhow, getting off topic here so back to the ABS Servo Unit:

Thanks again to DrFarkoff for the defunct ABS units

Since I have managed this I reckon anyone could give it a go if they know a spanner from a screwdriver - just go slowly and carefully and it's easy enough to disassemble and clean the unit.

Most of the work in removing the back subframe is at the back end. You might as well take it off the bike and have it grit blasted and hot zinc metal sprayed.
I was quoted £80 to do a Fiat Panda rear axle/subframe which contains a lot more metal that the bike's back end.

To get the whole subframe out looks like splitting whole bike in half - swingarm off, stands off plus brake lines etc. etc. Might be a bit too much for my skills

It is only the top half behind the battery that is rusty so might try painting that - see what it looks like and if no good then it might be teach myself time again

I patched up the paint on mine but when I got under and looked properly it was a shocking mess.
I can't remember if I disconnected the brake pipe but bleeding the back brake is easy enough to do.
The airbox and intake rubbers come off complete with the rear subframe.
Swing arm as well but you get chance to replace the bearings. They will be worn.
Clutch slave disconnects from gearbox so no bleeding needed.

Well done on that result

patience truly has won the day

Very welcome to old units I'd been meaning to strip them down and try and find the error source

But work and fixing bikes and house renovation seems to be sucking up any spare i have

DrFarkoff:

On the R1200 unit you sent I believe it was probably nothing more than the amount of crud inside it. I replaced my broken pressure switch assembly with the same switch assemply from this unit - most of the crud in mine was in the area of this switch assembly (including some corrosion on the inside ) whereas mode of the crud in yours was around ABS solenoids area.

On the R1150 unit you sent I believe the servo motors are both defective - I couldn't get them to run at all. However, some of the removable narrow oil pipes were the cleanest of the lot (corrossion on both the R1200 units) so I used them in my unit. Also one of the filters (underneath where brake pipe is connected) was also the cleanest of all the units so I used this along with the cleanest looking filter from my unit.

I'm convinced it's the crud and internal corrosion that causes all the problems - I would even go as far as saying it's the corrosion around my broken pressure switch that whilst maybe not breaking it certainly weakened the little circuit board on the switch. Shocked at how much corrosion could get into a supposedly sealed unit

As I say worth a try for anyone that wants to try and fix theirs - I have bits left over if anyone suspects any broken bits in their own and wants those bits for cost of postage.

Once again DrFarkoff - many thanks you are a top guy

Bendy Toy:

Thanks for your advice. I'll take a closer look at my rear sub frame and maybe start a different thread for help and advice on that if I decide to remove it completely - but spring is here and I might want to use the bike again for a bit before splitting it in half

Well played that man.

Hunda67, I've read your post with interest. Well done for persevering and getting fixed

Your last comments about internal corrosion are interesting. I wonder if the the corrosion is a consequence of the brake fluid not being replaced frequently enough (it is infamously hygroscopic) and not changing the fluid frequently is given as a reason for the units failing. The two would make a good cause and effect illustration...

Well done. Not a task for the feint hearted!

I am just about to embark on the same journey.. I hope my results will be as successful as yours... some background info on the BMBikes site..
http://www.bmbikes.org.uk/Forum/viewtopic.php?f=85&t=24844

farmerboy said:

Well done. Not a task for the feint hearted!

I am just about to embark on the same journey.. I hope my results will be as successful as yours... some background info on the BMBikes site..
http://www.bmbikes.org.uk/Forum/viewtopic.php?f=85&t=24844

Click to expand...

You may well be right but that unit has so many corners, nooks & crannies you could change the fluid every week and make no difference.

Well my brake fluid was supposedly last changed 4 years ago - told it was done by someone servicing the bike for me. I have to assume it was done but no way of being certain - this is part of the reason I will do everything I can by myself from now on (if you look on this site and many others there are lots of people with good advice and lots of people with good how-to instructions). My bike hasn't been BMW dealer serviced since 2009.

Now in those last 4 years the bike has had very limited use for various reasons and I am wondering if just standing there doing nothing allows for any crud to settle and maybe corrosion to start as nothing is moving in the circuits. I don't know it's just a theory. It is certainly my intention to do a yearly brake fluid change from now on in the hope that things stay working.

Farmerboy: read your link with interest - you certainly seem to be where I was with mine and your bike as done a lot more miles than mine. I figure you have nothing to lose (servosectomy was always my backup plan if I coudn't get it working) except a bit of time and effort. I did buy the right security bits (http://www.ebay.co.uk/itm/Silverhil...Set-10-Bits-/332157775941?hash=item4d56257045) to undo all the security bolts in the unit although I think others have managed to get them out by cutting slots in the heads etc. Will be interesting to know if you have a successful outcome as well - I hope you do

Thanks, I have been working on it today and seem to have cured the problem.... I simply removed and replaced the large electrical connector on the abs /servo unit and that "appears" to have resolved the issue. Weird.... ?

I still proceeded to bleed the system and so far everything is working as it should but I am concerned that I have not conclusively identified the problem...

some further info at the bottom of this page...
http://www.bmbikes.org.uk/Forum/viewtopic.php?f=85&t=24844&start=25

For the later 2007 onwards ABS unit repairs:

http://www.ecutesting.com/catalogue/product/bmw_r1200_abs_pump__ecumodule_combined_amc108473.html

Might also be able to do the earlier servo electronics ?

Glad you got it sorted farmerboy. For sure the electrics plug not connected correctly will cause problems. And I'm sure putting lots of fluid through will not have done the insides any harm at all.

I tried various places to have mine overhauled but the only one that said they could do something was https://rhelectronics.de/ in Germany at 900 Euro + shipping costs. They also said they could not guarantee to be able to fix it but would charge something for trying.