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ABS Issues- help!


barno68

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Let's start with some history... OCT 2005 I noticed that my front brakes were spongy and that the level was low, so I filled the MC. A week later the brakes totally failed (yep, nada...). So much for residual pressure for emergencies. So I took my '02 RT in to the shop. After three weeks they told me it would need a new ABS modulator to the tune of $2200. I talked to the mechanic about this as there was no visable leakage and the servos were running fine and he basically told me that they could not find anything else wrong so the ABS modulator must be the problem. Did not really give me a warm $2200 fuzzy feeling.

 

I decided to take the bike home and try to rebuild the module, but found that the brakes worked fine so I asked the service manager what was up. He said they pumped up finally but would bleed down soon. Sounded like a control circuit seal issue to me, so I gingerly road it home. The bike sat in the garage for three weeks and the brakes were fine. I rode it with no other issue than a lowering fuild level for the next 18 months. When I tore the bike down to tune it I saw that the module had been leaking so bought a used one to replace it.

 

Here is where I am at: front servo worked intermitantly (enough to bleed the system), but will not come on now. back servo starts when brake depressed, but continues to run after releasing brake. Only stops after bike turned off. Neither are getting power assist to the wheels, but manual pressure works at wheels. BTW this is the situation after swapping out controllers (using my old one) as the one that came with the modulator would fire the servos as soon as the key was turned on.

 

If it helps, I changed the oil, air filter, plugs, rebuilt the forks, changed the poly v-belt and swapped the front tire during this evolution. I also washed the bike once tore down pretty thoroughly to get the brake fuild cleaned off.

 

Any suggestions on what to try? I have already had this thing in and out three times, so am a tad frustrated... Thanks.

 

Brent

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If it helps, I changed the oil, air filter, plugs, rebuilt the forks, changed the poly v-belt and swapped the front tire during this evolution. I also washed the bike once tore down pretty thoroughly to get the brake fuild cleaned off.

 

Yeah, but did you replace the fairing screws with stainless steel ones?

 

Just kidding. grin.gif

 

Seriously, where was the ABS unit leaking? And, which circuit was leaking down (front control, rear wheel, etc)?

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Well, there was a couple of the go fast stainless screws missing wink.gif

 

I could not locate where it was leaking on the unit, but it was the front control circuit that was losing fluid. There were no pools of fluid, just dirt and dampness on the unit.

 

Brent

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We need some clarification...

 

This is a fully linked RT so I don't follow you when you describe one servo coming on at one time and the other not coming on at a different time/action.

 

There is only one servo motor on this bike. Either squeezing the front lever or pushing the rear pedal activates it. And it does so through micro switches at the pedal and lever. If you are not hearing the servo actuate when one or the other is squeezed/pressed, you need to go looking at the electrical activation circuit first before swapping modulators and what have you.

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Let's start with some history... OCT 2005 I noticed that my front brakes were spongy and that the level was low, so I filled the MC. A week later the brakes totally failed (yep, nada...). So much for residual pressure for emergencies. So I took my '02 RT in to the shop. After three weeks they told me it would need a new ABS modulator to the tune of $2200. I talked to the mechanic about this as there was no visable leakage and the servos were running fine and he basically told me that they could not find anything else wrong so the ABS modulator must be the problem. Did not really give me a warm $2200 fuzzy feeling.

 

I decided to take the bike home and try to rebuild the module, but found that the brakes worked fine so I asked the service manager what was up. He said they pumped up finally but would bleed down soon. Sounded like a control circuit seal issue to me, so I gingerly road it home. The bike sat in the garage for three weeks and the brakes were fine. I rode it with no other issue than a lowering fuild level for the next 18 months. When I tore the bike down to tune it I saw that the module had been leaking so bought a used one to replace it.

 

Here is where I am at: front servo worked intermitantly (enough to bleed the system), but will not come on now. back servo starts when brake depressed, but continues to run after releasing brake. Only stops after bike turned off. Neither are getting power assist to the wheels, but manual pressure works at wheels. BTW this is the situation after swapping out controllers (using my old one) as the one that came with the modulator would fire the servos as soon as the key was turned on.

 

If it helps, I changed the oil, air filter, plugs, rebuilt the forks, changed the poly v-belt and swapped the front tire during this evolution. I also washed the bike once tore down pretty thoroughly to get the brake fuild cleaned off.

 

Any suggestions on what to try? I have already had this thing in and out three times, so am a tad frustrated... Thanks.

 

Brent

 

Brent, as Ken said “we need more info here”.. Something doesn’t sound right with the servo running all the time..

 

I see you have an 02 RT? Any chance it is a police bike? OR, any chance you installed a police ABS unit if your bike isn’t a “P” bike?

 

Not really enough info here to help you much but I guess the preliminary info I would give you is to CHECK BOTH FRONT & REAR BRAKE SWITCHES to make darn sure they are not sticking & operating correctly.. Check right at the ABS unit to also eliminate a shorted wire between the brake switches & ABS unit..

 

Twisty

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This is an old argument for me; not all 2002 R1150RT's had fully integrated brakes. The early year models had partials and mine was one of the first produced for that model year (APR 2001). That is why the parts list shows two part numbers, one is for full and one partial.

 

There are two motors one the bottom of the unit, maybe they act as one servo, but there are two. Also, activating the front and rears together will step up the servo noise. So, can't really answer about them, but sure sounds like two of them grin.gif

 

I am leaning toward the electrical side myself, but do not know where to start. How do I trouble shoot the brake switches? Is it a straight ohm test (open/shut)? Which leads are they (at the ABS unit). I tested all the input to the controller when I had it off and all but the last one were either hot powered or grounds. I had assumed the last one was the ignition source. I did not check the leads going to the wheel circuit reseviors.

 

Thanks for the help in this. It would be nice to be able to ride again cool.gif

 

Brent

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This is an old argument for me; not all 2002 R1150RT's had fully integrated brakes. The early year models had partials and mine was one of the first produced for that model year (APR 2001). That is why the parts list shows two part numbers, one is for full and one partial.

 

There are two motors one the bottom of the unit, maybe they act as one servo, but there are two. Also, activating the front and rears together will step up the servo noise. So, can't really answer about them, but sure sounds like two of them grin.gif

 

I am leaning toward the electrical side myself, but do not know where to start. How do I trouble shoot the brake switches? Is it a straight ohm test (open/shut)? Which leads are they (at the ABS unit). I tested all the input to the controller when I had it off and all but the last one were either hot powered or grounds. I had assumed the last one was the ignition source. I did not check the leads going to the wheel circuit reseviors.

 

Thanks for the help in this. It would be nice to be able to ride again cool.gif

 

Brent

 

Brent, I don't know what to tell you.. Here is a scan (excuse the rather poor quality) of the standard NON (P) 1150RT ABS brake schematic.. This should be for most non police 1150RT’s but with you saying you have something different I don't know if it will work or not..

RTABSbrakes.jpg

 

Twisty

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No issue with either wheel ciruit, or the rear control side.

 

I would start with the front control circuit. Until you figure out where the fluid is leaking, I wouldn't pay any attention to the rest of the system. Find the leak, and you will likely find the problem.

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The leak was from the old ABS unit, it has been replaced; clean as can be now. The only thing I am using off of the old unit is the controller.

 

Brent

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Twisty,

 

Thanks for the diagram, too bad it does not give the pin numbers. I am having a heck of a time tracing the wires so can not really check the switches yet. The stumbling point right now is finding a pin of the right diameter to put in the ABS plug so I can perform continuity checks. The only thing that has fit so far is a staple and it is a tad small to make contact.

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Twisty,

 

Thanks for the diagram, too bad it does not give the pin numbers. I am having a heck of a time tracing the wires so can not really check the switches yet. The stumbling point right now is finding a pin of the right diameter to put in the ABS plug so I can perform continuity checks. The only thing that has fit so far is a staple and it is a tad small to make contact.

 

Brent, be very careful testing those ABS terminals.. If you force ANYTHING in those female terminals you will open them up & then you will have a whole new set of problems down the road.. Those pin type terminals are a very precise fit & tension so be careful..

 

I have a very good selection of Bosch terminals so if you can give me the EXACT O.D. of the male terminals I probably have some,, problem is you are a long ways away so the snail mail time will be long..

 

Twisty

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Twisty,

 

Thanks, that is a very kind offer. I think I may be trying too had to say a buck (a few thousand in this case) and might have a captibility issue. The new unit is a partial iABS off of a '03 R1000S and I had heard that the only real difference was the controllers. That may still be true, but this does not seem to be working. I tell you this, they look identical and the wiring inside the controllers is alike. Who knows...

 

I think I will pull this new unit out, tear down my old one to see if I can find the bad seal. I can always scavenge parts off the other one.

 

The thing that really chaps me is that neither unit have the right part numbers for the bike they came off of and when the numbers that are stamped on them are run they come up as invalid. The ABS system is my only big complaint about the RTs and by what I have read it seems to be a fairly common failure that is not repairable except by replacement. Hopefully the newer models have a better system.

Enough of my ranting...

 

Brent

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