Is there a recommended procedure to flush old fluid out of the ABS Modulator?
I can see doing a first flush, then some gravel braking to activate the module, and then reflush, but is there a way to do it all in one session?
Flushing the ABS modulator?
- Thread starter MidLife
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Is there a recommended procedure to flush old fluid out of the ABS Modulator?
I can see doing a first flush, then some gravel braking to activate the module, and then reflush, but is there a way to do it all in one session?
Is there any need to do this? The service manual makes no mention of needing to flush the ABS module.
It’s not a car, following the correct bleeding/flushing procedure will do it.
OP
OP
That's what I was wondering about.
What happens over time to the fluid trapped in the ABS module, that stays there as long as the ABS is not triggered?
Maybe it is isolated enough to prevent degradation?
Some newer bikes have a procedure to electronically cycle the ABS module with the bike standing while flushing. So, it seems there are manufacturers who do think that dislodging and flushing any trapped ABS fluid could be beneficial?
A poor man's approach for the ST could be to activate the ABS (on gravel for instance) just before a flush, which would have the ABS trapped fluid only one flush behind the current one.
I'm far from knowledgable about such things but my understanding of ABS pumps was that they relieve and restore line pressure without actually flowing any fluid. Based on the diagram in the ST1100 manual, the wetted side of the ABS piston is fully exposed to normal fluid flow when bleeding the brakes so will get flushed out.
OP
OP
Good to know!
Last trip at the shop they were doing a flush job on a BMW 1000 RR and were hooking up a gizmo to it for ABS activation while doing so, which got me curious.
My first ST had no ABS, so never worried about it.
My car mechanic also says some of the cars he works on call for ABS activation for flushing and some don't, and, as you said, the manual would specify it if required.
Thanks!
ST1100Y
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I'm with @Igofar in this, I just use lots of fluids...
When I got the '07 NT700VA for my GF in 2019, it had 36,000km/22,500miles on, and it should have had a complete service record...
Brake checkup was among the first things I did...
So I hooked up my trusty, air-powered vacuum device and started flushing in the sequence given in the OEM service manual...
yellowish... yellowish... darker yellowish... suddenly lumps like squashed bananas appear in the clear silicone hose...
so I kept drawing & refilling... maintaining a steady flow... and I kept going till finally all waxy flakes had vanished...
and then repeat from the top with another bottle, just be sure...
At the end it required 4 new, freshly opened 12oz bottles super DOT4 to get rid of all the goo... and a 5th for my piece of mind...
Seems whoever previously worked on it, never cared to truly flush the system... all the crap must have stuck/accumulated inside the modulator... $$$!
And the NT's ABS/CBS has a rather simple plumbing compared to what's on an ST1300...
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Again, it’s not a car, nor a modern BMW motorcycle, that requires it to be flushed a certain way, with only their equipment.
The system Honda uses is different, and there is no need to try and activate the ABS when flushing or bleeding the system.
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This is the diagram from the ST1100 service manual showing the "new" ABS system in the TCS model; remarkably simple in construction.
OP
OP
Nothing I could find like that on that in the 1300 manual.
There is more doc on the 1100.....maybe because it was more prone to failure?
ABS 1 - Modulator Assembly Tutorial ( ST1100 ) *
ABS 1 - Modulator Assembly Tutorial ( ST1100 ) *
www.st-riders.net
This schematic makes me wonder how the chambers are bled, as it is not clear how fluid could be entrained out of them while flushing. But from what @ST1100Y is describing, somehow, it happens!
That diagram is the "old" ABS, the new one is the diagram I showed. Since that was on the 1100, I think it is reasonable to assume the new version is on later bikes like the 1300 as well. Honda service manuals helpfully have a "technical features" chapter at the back which they populate with any novel tech on that model. ABS was old-hat by the time of the 1300 so the manual instead talks about the balancer shafts IIRC.
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