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Discussion Starter #1
About 2 months ago my ABS pump would run after shutting off the car. So the firstr thing I did was try to replace the relay. That did not make a difference and the ABS pump quit working. So I drove the vehicle for a while with no ABS. One day the brakes completely failed. Pedal to the floor no pressure, etc. The fluid is still present, so it was not air in the system, just a lack of pressure. Now I am trying to get my head around a good testing procedure to determine exactly what should be replaced.

So my first question to anyone with brake experience is:

If you are running the brakes without ABS, is the Accumulator still part of the system? If so, is it possible that that is what failed when the brakes went completely out? Obviously I would like to avoid having to replace the booster, so I am wondering if this problem is still isolated to the ABS and Accumulator?

Any help would be appreciated.

2001 4.6 HSE
 

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I've just gone through a similar experience in completely losing brake hydraulic assist. Culprit was the abs pump not pumping (the one right next to the EAS box, with Wabco stamped on it and with fancy green anodized connector). In my case, going through all the electrical connections restored function-No parts required.

But, first, it sounds odd that your abs pump was turning itself on after you turn off ignition. I don't think it's supposed to do that, so I would diagnose this situation first. If a new relay didn't fix it, possibly the fusebox itself is the culprit.

Anyway, when you lose the assist, most likely, it's the abs pump malfunctioning.
 

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if your brake pump has been running when it should not have been,there is the possibility that the pump motor has been burnt out.Check to see if it is running just after you start the engine.If it is not then there is the place to start,to find out why it isnt running.
 

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Discussion Starter #4
I am going to run some tests on the ABS pump to determine if it is electrical or if the pump burned out.

Does anyone know definitively if the Accumulator is part of the system if you are driving the vehicle without the ABS pump? Since it is attached to the ABS pump it makes me wonder. Maybe the brakes completely failed on account of the accumulator rupturing and all the pressure disappearing?

Ultimately I would like to rule out the Booster if possible.
 

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When the hydraulic pump runs it builds pressure in the system via the accumulator. The energy is stored because the accumulator bladder is compressed and allows a volume of brake fluid to be retained for assisted braking. When working on the brake system one first pushes 30 to 40 times on the brake pedal {all things are off} to eliminate the brake fluid from being under pressure. A member on this forum who had a ruptured accumulator would hear his pump run for only a few seconds at a time since there is no gas behind the accumulator bladder to compress and hence provide a reserve of pressurized fluid. The nitrogen {I believe} gas behind the accumulator bladder will now be interspersed in the brake fluid thruout the vehicle. This would also create a spongy pedal since all this gas would have to be compressed before brake fluid could actually push on the caliper pistons, and hence require a full bleed after repair to get this gas out of the system. If you are sure the pump ran with vehicle off I would agree with above responses that something is wrong with that type of operation. Just to be sure that it was not the air compressor running since I believe it can run for up to a minute on opening and closing the door {I can't remember if the key has to be in 1st position for this to occur] If you drove the vehicle with no pump for a period did you experience the need to increase pedal pressure with subsequent stops. I would assume that some dash lites would have stayed on during this period. You might want to discuss this problem with HSE on this site. I have never read any info that a faulty master cylinder would prevent the pump from running but HSE might be able to enlighten us on that point. Keep us posted.
 

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Discussion Starter #6
My first sign of a problem was when I shut the vehicle off and the ABS pump stayed on. I just happened to be in the garage so i noticed it. To turn it off I wiggled the relay, black #17. A couple of other times I noticed the ABS stay on, but I caught it right away and jiggled the relay. Then the ABS went completely out and there was nothing I could do. All 3 dash lights came on and stayed on. I tried to replace the relay with a brand new one, and that did not get the pump to go on. I found the vehicle still had braking, but I would have to give the brakes a pump or two to stop. So I drove the vehicle like this without any problem for about a month. All of a sudden the brakes went completely out. No ability to pump them to increase pressure, just a sudden loss of pedal and pressure. Fluid reservoir unchanged and full. So here I am trying to figure out how to approach the repair. If the accumulator continued to operate after the ABS pump quit working and provided the braking pressure, then maybe the failure of the accumulator finally caused the failure. This is what I am trying to determine now.
 

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Not sure if this is gonna answer your question regarding the function of the abs accumulator, but I've attached couple files from the workshop manual of Alfa Romeo 75/Milano that I think uses a similar ABS system.
 

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"You wiggled the relay and caught it"
That means you were at the source of the problem.
"You replaced the relay and now it doesn't run at all"
That means the relay is not the problem.

The only thing left at the point of wriggling is the connections at fuse box itself.

I would say that the relay socket and/or connections are now shot and you have an open circuit there.
A common problem in these trucks.

Unbolt the box and check out underneath. also check with meter for continuity from pins above to wiring loom before buying a new one.

P.S. disconnect battery first.

Cheers
 

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Keijo said:
"You wiggled the relay and caught it"
That means you were at the source of the problem.
"You replaced the relay and now it doesn't run at all"
That means the relay is not the problem.

The only thing left at the point of wriggling is the connections at fuse box itself.

I would say that the relay socket and/or connections are now shot and you have an open circuit there.
A common problem in these trucks.

Unbolt the box and check out underneath. also check with meter for continuity from pins above to wiring loom before buying a new one.

P.S. disconnect battery first.
I agree,but the pump may be gone as well. These pumps have a short duty cycle, if they run continually for spirts of 30 minutes plus. This can finish them off.
Regards Russell.
Cheers
 

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Discussion Starter #10
Still wondering if the Accumulator is part of the braking system in the absence of the ABS pump? Can ayone confirm this? If I resolve the electrical and find out the ABS pump is good, maybe when the brakes failed it was the accumulator?
 

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Read the NO BRAKES, HELP response by Jos. He has identified a potential problem in that the pump may be starved for brake fluid if the line feeding the pump does not allow fluid to flow from the resevoir to the pump. There has been an earlier post that mentioned this issue. When you read the above post for pump assisted brake fluid it details the purpose of the accumulator which is to store a resevoir of energy for assisted braking. There are no electrical connections connected directly to the accumulator or booster but the overal pressure in the system dictates what happens. Therefore if no pressure the pump should run until the pressure builds and electrically shuts off the pump. So if you have no braking it really should mean that the pump would run. It seems unlikely that you would have enough pressure in the system to shut the pump off yet have no brakes. Somehow you will have to figure out if you have voltage to the pump motor. I don't personally know which wires would be the proper ones to test but hopefully there is an electrical diagram which would help you find this. There is a pump rebuilder in California I believe and this has been mentioned in other posts. If I remember correctly the pressure switch for the pump is not available as a separate part. Rebuilt pump c/w accumulator is 500 and change. Someone from England mentioned getting one for a fair bit less. If you removed the accumulator and the pump ran [but not because you removed it]it would shoot fluid out of that port under pressure so that would not be the thing to do. If you do remove the pump to test it on the bench I would be very careful that no pressure is in the system and the high pressure line to the booster should be loosened very carefully to protect yourself. I have not read specific details on removing the pump but again our HSE member should be able to confirm the appropriate procedure or, hopefully someone can direct you to the appropriate procedure in the shop manual if it is there. My response is based mostly on the point that I am very interested in understanding this system and have done some thinking about it. As many on this site, I have changed the accumulator but have not had the deeper issues that you are obviously facing. [yet]
 

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I just read HSE posts on pges 26 and later. Please review pertinent info by HSE. It will clarify what you need to try and how. Thanks Russell.
 

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diff said:
I just read HSE posts on pges 26 and later. Please review pertinent info by HSE. It will clarify what you need to try and how. Thanks Russell.
No worries, pleasure.
 

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Ok, as diff pointed out the accumultor is there to store energy. Around 30 pedal applications of reasonable stop pressure. It does form part of the pressure circuit and helps with braking performance under normal engine running circumstances. It's also a failsafe backup should the vehicle have a complete electrical melt down, meaning the vehicle will still have around 30 pedal applications to stop the vehicle with zero electrical or engine power. I have in the past completely disconnected both abs pump and modulator to test the hydraulics in the brake system. The brakes are stil reasonable in this condition.
As diff said also, I would check that you have pressured fluid at the modulator. Loosen the banjo fitting and point the flexable pipe at the ground, have someone turn on the ignition to start the pump. You should have good pressure here.
I'm also concerned about the pump not shutting off after the car is turned off. This should never happen. The relay, like you is the first item I would have changed, then if this didn't cure the problem I would give serious thought to the fuse box. Make sure that you check the fuse in the BECM. I had one that had a dirty contact that played havac with the electronics. I was getting strange messages and faults.
Have you had a diagnostic hook up yet??? This wouldn't hurt just to help with the problem.
Regards Russell.
 

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Discussion Starter #15
I think that a couple of things are possible here. Since I had a problem with the relay not shutting off the ABS pump after the ignition was turned off and jiggling the relay turned off the pump in this situation, I think I will have to look at the possibility that there is no solid connection to the pump from the relay, and this is why the pump is not working. After I experienced the pump not starting under ignition with the relay in I just assumed I burned the pump. So I took the relay out, so as not to have it burn out as I just paid $60 for it, and it seemed that it was running hot when I left it in. So I think I need to get power to the pump to see if it is actually working or not. And I will need to check that fusebox to see if the realy is actually supplying juice to the pump.

Secondly, after the pump stopped working and I removed the relay, I drove the vehicle without ABS successfully for a period of time. I think it is safe to assume that the Accumulator was part of the manual system based on the drawings supplied. So to have a sudden failure of the brakes couod mean that the accumulator finally failed. It is most likely the original as I have owned the truck since it had 45K on it and there is 115K right now. I believe I saw in another post a procedure for testing the accumulator off the vehicle, poking a needle into it or something like that.

So it is quite possible that the ABS pump is actually good, but the accumulator is failed and the realy circuit is faulty at the fusebox. This is the premise I am going to go on.

Thanks everyone for all your feedback so far. It is very helpful.
 

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Just my little addition here, brake fluid reservoirs are becomming a issue where pipe to abs pump is connected is a fine screen filter within container which does block up after years of neglect in such sense where brake fluid is not being replaced every 2 years.

This container is available loose either through agents at a massive dent to your pocket or from Britpart and a resonable price (Same Wabco brand)

The black relay if old should also be replaced as a precuation, the older ones contact within like to fuse together and the pump runs on, fuse boxes are a issue here too in this area, dont get them wet.
 

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1959mvp said:
I think that a couple of things are possible here. Since I had a problem with the relay not shutting off the ABS pump after the ignition was turned off and jiggling the relay turned off the pump in this situation, I think I will have to look at the possibility that there is no solid connection to the pump from the relay, and this is why the pump is not working. After I experienced the pump not starting under ignition with the relay in I just assumed I burned the pump. So I took the relay out, so as not to have it burn out as I just paid $60 for it, and it seemed that it was running hot when I left it in. So I think I need to get power to the pump to see if it is actually working or not. And I will need to check that fusebox to see if the realy is actually supplying juice to the pump.

Secondly, after the pump stopped working and I removed the relay, I drove the vehicle without ABS successfully for a period of time. I think it is safe to assume that the Accumulator was part of the manual system based on the drawings supplied. So to have a sudden failure of the brakes couod mean that the accumulator finally failed. It is most likely the original as I have owned the truck since it had 45K on it and there is 115K right now. I believe I saw in another post a procedure for testing the accumulator off the vehicle, poking a needle into it or something like that.

So it is quite possible that the ABS pump is actually good, but the accumulator is failed and the realy circuit is faulty at the fusebox. This is the premise I am going to go on.

Thanks everyone for all your feedback so far. It is very helpful.
ok, try feeding power straight to the pump via the main white connector on the pump. By memory there is a red and black wire, black being earth. Regards Russell.
 

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On my above post I wrote that there are no electrical connections to the [what I call the master cylinder] That is wrong! I looked at it last nite and there is a connection to it, so strike that sentence. :oops:
 

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diff said:
On my above post I wrote that there are no electrical connections to the [what I call the master cylinder] That is wrong! I looked at it last nite and there is a connection to it, so strike that sentence. :oops:
Correct, there is a power /earth plug as well as the multi pin plug which is the comand for solenoid response to the modulator.
Regards Russell.
 

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I am having an issue with my 2000 Rover. He isn't breaking properly. We bled the breakes today, including the ones under the hood. Unfortunately, it wasn't the problem. I tried (engine off) pressing on the break until I had resistance and then turned it on. The break went down for a moment. The relays and fuses are all good. My front breaks bled very good but the back ones didn't bleed fluid and no air either. I hope this isn't a problem with the booster. My front breaks work but rears do not. Maybe the proportioning valve is the culprit? Any advice would be greatly appreciated
 
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