Lizard928

Jon,

I will know in the morning (need to bleed the system), as to if it all works as planned.

As well to further update this though.
I pulled off the two bolts off the bottom. Inside of them is an aluminum plunger, a spring and then the nut.
From my inspection of the system this appears to be an accumulator of sorts. The ABS engages, and what it bleeds off goes into these ports pushing the piston down compressing the spring. Brakes/ABS released and the spring pushes the fluid back up and into the system/reservoir.
The side that was leaking (front), the piston was moving properly but the o-ring seal was buggered up from junk build up from a lack of use/fresh fluid in the system. It had turned into almost like dried cat urine.
The side that was not leaking I decided to inspect as well. The piston was stuck in the maximum pressure location from more of this junk build up.
However this seal was OK. However I would not trust standard o-rings in an ABS/brake fluid system. The stock o-rings were still very soft and pliable, and it was very obvious it was the build up of junk in the otherwise perfect bores that caused a wear to the seal.
I got the other piston free and have just put it back together for now. However it is obvious that the solenoid is leaking too or this would not have leaked until the ABS was engaged.

However this shows to me that if on this car the ABS system was engaged, it would have literally shot fluid out the bottom of the ABS pump causing a massive loss in fluid.
The other accumulator in the ABS pump would have simply built up pressure. This would have then balanced pressure between the two halves, rendering that half of the ABS pump useless.

I am actually considering pulling the ABS pump out of my car and cleaning these cavities and reassembling once clean to ensure that the system is in proper working order.

I also remember Nicole (Hooked on cars), has had a never ending problem with her car that she has too much pedal travel. Multiple master cylinders have been tried as well as numerous other things.
It might be worth it for her to swap in a new/good used ABS pump assembly as if the solenoid seal is shot it will cause her to have to be pushing down these accumulators first, and lessening the effectiveness of her ABS.

Nicole

Interesting theory! Since the bias valve has been replaced, the car seems to brake much better - perhaps better than before. However, the pedal travel still seems a bit long, and the pressure point a bit softer than what I "think" it was before.

But then again, the car sat for 9 months while we were trying to figure this out... I might not remember exactly what it was like.

I have been wondering, if the new brake lines might be soft, and if some metal mesh lines would be worth a try.

jon928se

Just thought I'ld post these for reference - only one solenoid valve is shown but there are three - FR FL and Rear all controlled independantly. To the best of my knowledge there's only one reservoir (g)

Pressure building phase - wheels not skidding ABS not activated



Pressure Holding Phase - ABS activated holding brake fluid pressure at the wheel



Pressure dropping phase - ABS activated reducing pressure at the wheel



Operation is very simple.

The solenoid valve (c) has 2 positions
Ppressure holding phase is activated by a voltage of ????? (at a guess around 6 or 7 volts) - but it generates a current of 1.9- 2.3A in the solenoid

Pressure reducing phase presumably activated by battery voltage - 12v generating a current of 4.8-6.0A.

The pump motor (M and h) runs all the time the ABS system is activated.

jon928se

A leak at the solenoid valve (c) piston seals would result in no external leakage but would allow fluid to transfer into the accumulator (g) - with more pedal pressure the spring would compress giving the symptoms I've had and Nicole had - ie a long pedal that feels soft - but when you push hard and far enough and fill the accumulator you would then get normal braking.

Colin - can you clarify which seals you found that were leaking/buggered from passing over the dried cats pee?

Lizard928

Jon,

First picture is of the accumulator piston assembly with retaining bolt.
Second picture is the cavity in the pump which the accumulator slides in and out on.
The piston shown is the one that was stuck in the retaining bolt, in the pressurized position.
On the piston is an o-ring. This o-ring is the one that was buggered on the other one.

While the pump may have 3 solenoids as you say. I can only see two on the system, and two accumulators.

Sorry about the crap picture quality, these were taken on my iPhone.

Lizard928

However to clarify further Jon,
I believe in Nicole, and your case, that the seal on the plunger activated by the solenoid is what is damaged.

I will plan for further disassembly and see if I can get a source for seals that will withstand brake fluid.

Lizard928

An update on this.

The 87 pump with 90 circuit on it functions properly. ABS engages properly. No pedal sink.
ABS light remains off indicating that system is working properly.

But I am having an odd symptom.
With car off and brakes bled pedal is rock solid with VERY little movement. I have confirmed brake master freeplay as well as bled the master.
However the moment the booster gets vacuum. The pedal sinks substantially before building the needed pressure to stop.
System is fully bled and shows no sign of air.

Nicole

Same here.

Lizard928

What is interesting is that the ABS pump used here had a perfect pedal on the car that it came off of, and it has not been out of the closed system for very long.

I will be attempting a power bleed tomorrow.