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Today at Atelier Kaz - Private NSX Enthusiast, ex-Honda R&D engineer with F1, Indy/CART background

ABS Solenoid (Classic 1st and 2nd generation) 01

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[ Apr/2020: Still in the process of updating. ]

Hope followings will assist some of you when dealing with the classic ABS that has leaky/stuck solenoid issues.

1. The Basic

You can find the system diagram, construction and operation info through the workshop manual.
Please take a look before going any further.

Click image for larger version. 

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The design of the classic ABS changed several times during the production but the major one happened during 91 - 92.
For the ease of explanation, the original one would be named as 1st generation (1st gen.) followed by the 2nd gen. in 91 - 92.
For Type-R and 97+ brake system, the ABS setting (piston spring + software) was changed but again for the ease of explanation, they will be categorised as 2nd gen.

The easiest way to distinguish them is the shape of the reservoir.

When looked from the top, the 1st gen. has square shape.
The 2nd gen. one has protrude section.

Some comparison photo here;

With 2nd gen., Honda modified the package design of the solenoid in order to improve the reliability issues experienced with the 1st. gen..
It changed the design so that two solenoids were packaged as a set.
Still, unfortunately, it's not free from issues and even the 2nd gen. one can experience both the leaky as well as stuck closed solenoid issue as seen on the 1st gen. one.
It just has better chance of surviving longer without these issues but eventually, it will end up with the same issue if not serviced properly.

2. Pre-Caution

Please note that the advice such as 'exercise ABS regularly', 'apply brake on the gravel or wet surface multiple times' or similar could result in extra issue.

You will find the photo of solenoid later but at the inlet entrance and exit, there is a meshed filter at both sides.
This is because

[ Mention the issue of activating ABS pump immediately after triggering the ABS solenoid, aerated fluid overflowing from the top of the reservoir, etc. ]
[ Mention the air getting into the piston side of the modulator and can't be bled using the danoland method. ]

In this blog, it is based on the 1st gen. but the basic concept applies to the 2nd gen. as well so this will help understanding the aspect of 2nd gen..

The famous ABS flushing method at danoland website;

Will touch on this later but please note that the method in the above link can only flush the solenoid side of the system.
It won't do anything at the piston side.

Warren's detailed rebuild doc ver.6;

Although the o-rings for the piston side is NLA, the ones for the solenoid are still available and can be sourced from your local Honda/Acura dealers.
For majority of the owners, servicing just the piston side could be enough to fix one's issue.

Also, high pressure fluid is dealt with inside the cup section of the piston.
The external o-ring around the piston body is more of dust seal without encountering the high pressure fluid from the accumulator.
Therefore, at your own risk, you may be able to re-use them.
Or, just measure the size and place order on some of the o-ring companies on the web.
There will be a minimum order number such as 50 or so but it's available.

You must select EPDM or equivalent that can handle the chemical aspect of brake fluid.

Will touch on this later but please note that replacing the o-ring WILL NOT fix the leaky solenoid issue if it was caused by the contaminated inlet valve seat area or by the weakened/failed valve return mechanism.
You will see the diagram explaining this later.

Replacing the o-ring is only effective if the leakage happened through the o-ring as described in the diagram later.

[ put parts no. for the o-ring here.]

[ May want touching on the ABS pump failure, error code #1, punctured accumulator here or at the next post. ]

[ Touch on ABS pump test, accumulator test in conjunction with the pressure switch status, before start disassembling. ]

Updated 13-04-2020 at 12:06 PM by Kaz-kzukNA1

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