[allensp38]

I have a 2000 Range Rover and last week the brakes went out. I've been doing a lot of research on the subject and from what I've read and been told, I have a faulty accumulator. Typically, when the accumulator goes bad it's because the nitrogen charge drops out of spec. causing the ABS pump to run too long and too often, but the brakes still work. In my case, the ABS pump runs for about 5 seconds when I turn the ignition switch on but the brakes have no power assist so basically, no brakes. There are probably two types of accumulator failures, one being low pressure on the nitrogen side and the other being a ruptured diaphragm. In the case of a ruptured diaphragm, I believe the system will build pressure until the pressure switch shuts the pump off like it's suppose to, but because an accumulator with a ruptured diaphragm is like no accumulator at all (assuming it's completely full of brake fluid), there is no compressible space in the system to build pressure. What little residual pressure that is there from running the pump 5 seconds is depleted immediately when you touch the brake pedal resulting in no brakes.

If anyone has any information or knows the symptoms of an accumulator with a ruptured diaphragm please comment. Like most of us here, I want to understand why the system is behaving like it is and not throw parts at it blindly.

Allen

 

[FSO]

Hi is very ezy to check if accumulator is ok.First depressurise the break system.
Them unscrew the accumulator.Make sure to put rug under the accumulator.If the bladder is split the accimulator will be full of break fluid .If the bladder is a ok but the press is low. To check this, when you take the accumulator off push small cable tie in the hole on the bottom of accumulator if it go more them 1 inch accumulator is no good.

 

[allensp38]

Thanks for the suggestion. I'm out of town at the moment but I'll check it out this weekend.

 

[diff]

I've not had a ruptured accumulator but a member here has posted the exact same results as yours. ie pump would run for 5 sec. and again after one press on the brakes due to no resevoir of pressurized fluid. If yours did rupture then you likely have fluid which contains the released nitrogen gas. If so a brake bleed following proper procedure would be in order to optimize brake effect. I have found air at the lowest of the three bleed screws on the master. I put a rag below and opened slightly and bubbles with a bit of fluid came out. Then I closed it. I have done this a few times and must do the full bleed as well. Others have mentioned that air can remain trapped in the system so it may take more than one attempt to minimize [eliminate] air. It has been noted that when accumulator is changed a bleed may not be necessary. A touch of fluid can be placed where accumulator screws in and in orifice of accum. ball as well before screwing into position. Lots to read about this issue on this site.

 

[allensp38]

All the sysptoms pointed to a faulty accumulator so I replaced it and my brakes came back to life. I removed the old accumulator and inserted a cable tie into the hole on the bottom (as suggested by FSO) and it went in more than 1". I also inserted the cable tie into the new accumulator and it also went in more than 1". I cut the accumulator open and the diaphragm appears to be a rubber membrane with a dome like configuration attached to the side of the metal sphere. If you look at the photo, you can see where the diaphragm has been torn away from the inside of the sphere.

 

[thesloan]

To replace the brake accumulator, can I just essentially unscrew the old one and screw in the new one?

Some people have said here, the system needs to be depressurized, but then also read that doesn't have to be done. Also read brakes need to be bleed too?

 

[RRToadHall]

Have you read the procedure in RAVE as suggested in the other thread you are bumping? To depressurize step on the pedal 30 some odd times. Clean the old one, unscrew it, make sure the threads are clean and screw in the new one. If you have issues bleed the system although it is rarely if ever required. If you have to bleed, follow the directions in RAVE.

 

[thesloan]

No...haven't read that yet. But OK...thanks for the how to tips.

 

[RRToadHall]

RAVE should ALWAYS be your first reference. SEARCH should be your second reference.