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Old 04-19-2022, 10:44 AM   #1
JKLedbetter
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Default ALB Pump problem

The ALB pump on the '89 started running continuously, until the ALB computer would shut it off and illuminate the ALB light on the dash.

The fluid level in the ALB reservoir looks normal, which would seem to rule out an external leak.

The two most likely possibilities I could think of were that the pump mechanism has failed (not the electric motor that drives it), or the solenoids in the modulator are letting fluid leak through.

Using my homemade tester I briefly activated one of the solenoids in the modulator and the fluid in the reservoir began to foam. I think this indicates that there was still some pressure in the accumulator, which rules out leaking solenoids, but I don't understand how air got into the system to cause foam.

I then ran the pump motor for several seconds, but the fluid in the reservoir did not drop, nor did the pump sound like it was building pressure.

I relieved the rest of the pressure with the T-wrench, though there wasn't much, not even enough to push fluid all the way up to the T-wrench reservoir.

I am leaning toward the pump being bad, but I don't understand the foam.

Can any of you help me understand the foam?

Do any of you have a pump to sell?

-Kennon
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Old 04-26-2022, 10:56 AM   #2
paulo57509
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It's been a long time since I did anything to the ALB system in my coupe so the memory has faded. The following is a Honda Tech-2-Tech document I downloaded 5-6 years ago from a now defunct website. Might have been a link from an NSX forum (??) Because of super small upload data limits here, I'll just cut and paste portions from said document. Since the ALB light is on, have you checked the ALB controller for codes?

IMO, if there's foam in the reservoir, the system is sucking air from a leak. There are a lot of places in the system where the leak can occur. I've always believed that a runaway pump is due to internal leaks in the Modulator.

Hopefully, the following will help. It's the most common ALB issue.

The ABS ECU will usually store a code #1 if system pressure is the problem. Code #1 indicates pump is going over it’s run time, and is somewhat common in a lot of the Honda and Acura models. The most common problems are leaks, either internally in the modulator solenoids or externally in the hoses and "O" rings.

We have come up with some additional steps to determine whether you need to follow the troubleshooting tree in the service manual for code #1. This test is only good for the systems with the separate modulator/reservoir assembly.

- If the car is equipped with a service check connector; connect it to read the code from the check engine light. If it is not equipped with a service check connector locate the ABS ECU to read the code from it's single LED.

- Turn on the key, the code should start to flash after 10 seconds or so. If code 1 is present continue with this
procedure.

- Code #1 is usually caused by leaks, or material lodged in the ABS system solenoids, which causes stored high accumulator pressure to leak off. Lack of periodically using the ABS system can cause the solenoids to become stuck open with contamination, which will allow the pressure in the accumulator to be lost and the modulator reservoir to overflow. This can be corrected most of the time by exercising the system or making it operate 6-10 times on a loose gravel road or soft shoulder. Remember that all three solenoids must be operated for this to be effective. (both front wheel sensors and at least 1 rear sensing wheel lock) Also remember the reservoir must be full before performing this procedure.

- If the ABS pump runs for more than 2 minutes (45 or even 20 seconds on some models) the system will turn off, ABS light will come on & code #1 will be indicated from the ABS ECU. Stop the car turn off the key, and then restart. This will reset the indicator light. The code will stored in the ECU. Quickly accelerate and then lock the brakes to make the system operate 3-4 times before the pump goes over it's maximum run time. Make sure you have plenty of open area (and no traffic or other obstacles) on an icy or gravel road and you don't need to go too fast to make it work. You will also need to bleed the ABS system 3-4 times to thoroughly flush the system to finish the job. Remember that the ABS fluid is separate from the regular brake system fluid but, still needs flushing every 30k mi.

- If the pump still goes over it's run time, bleed the accumulator to see if it has any fluid at all. If no fluid comes from accumulator, locate the pump relay (usually in the under hood fuse box). Connect a momentary contact (or starter switch) to pump relay terminals to operate the pump manually.

- Remove the fluid from the modulator reservoir. (photo #2) Operate the pump momentarily and see if fluid is coming back into the reservoir from the solenoid ports located in the modulator reservoir. This will indicate the solenoids are stuck open and a new modulator is needed.

(do not run the pump excessively or you could over pressurize the system. The system has a high pressure check valve to relieve high pressure, but the pressure switch operation could be affected).

On most models you can remove the reservoir to get a better view of the tops of the solenoids.

- If no fluid comes from the solenoids and the pump runs, but will still not pressurize the accumulator the pump is bad.

- If the pump does not run, troubleshoot the pump electrical.

- If you discover metal particles in the bottom of the ABS reservoir while checking fluid, indicates major pump problems. Metal contamination may not flush completely out of the solenoids. The pump will need to be replaced first to find out if the modulator can be flushed. Make sure you clean out the ABS reservoir of any metallic particles before replacing the pump and flushing the system. If the modulator solenoids continue to leak, the modulator assembly must be replaced. This procedure can get very expensive very quickly. Make sure your customer knows what he/she is getting into first.
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Last edited by paulo57509; 04-26-2022 at 11:02 AM.
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