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1995-2002 Range Rover P38A
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Hi, I´ve recently bought a P38 Range Rover and the latest issue (of many already!) that I have experienced is somehow related to the braking system.
Both ABS and emergency brake lights come on at every first push of the brake pedal meanwhile I can hear the pump running.

Looking at this page
http://www.rangerovers.net/repairdetails/braketc/abs.html
I guess that the problem lays either on the accumulator or... somewhere else!

I followed the instruction for the diagnosys and the pump did cycle on repeatedly during the 5-minute wait, now what is "unclear" to me is the "some sort of internal leakage (probably a seal, or check-valve)".
I would change the accumulator but I feel that may not cure the issue.
Which "seal" or "check-valve" should I check?
Should I better change the accumulator and its electric pump or the whole ABS/master cylinder box?
 

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1995-2002 Range Rover P38A
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Change the accumulator and start from there.
Other problems would probably be related.
Throwing entire assemblies at the problem will just cost a lot of unnecessary $$$
 

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1995-2002 Range Rover P38A
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Hi

There is a brake light switch connected at the brake pedal. This brake switch has a NO and NC contact both connected to the ECU. When the ECU detects that the signal of one of the switches changes and from the other not, the warning light comes on.
You can check if this problem is causing the trouble with your car with the help of a simple multimeter. The ecu resets when you cycle the ignition for some time but eventually it will log a hard fault which needs to be reset with diagnostic equipment.


As for the accumulator, this is just a rubber bag filled with nitrogen at a preset pressure of around 80 bar. When the pump build up pressure the rubber bag is squeezed smaller and the nitrogen compressed further. This process continues until the pump is stopped by the pressure switch. At that moment the nitrogen bag has become very small and it functions as a buffer. When brake fluid is moving elsewhere through leaks or usage, the nitorgen expands and keeps the pressure of the system to lower much slower then it would if there is no accumulator. This causes less starting and stopping of the brake pump and longer runs of the brake pump to recharge the system agains the accumulator pressure. If the accumulator is faulty the brake pump runs with small burst and can burn out as a result of too many starts and stops.

Best regards

Jos
 

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Do you hear the pump kick on almost every time the brakes are depressed? Mine has been doing that off and on. The brakes feel strong, but I hear that pump quite often. I read that the accumulator stores enough energy for ~30 brake applications, so I'd have imagined that pump would only come on once in a great while?

If it's kicking back on within the 5 min window wouldn't that imply a leak somewhere in the brake system rather than a bad accumulator?
 

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1995-2002 Range Rover P38A
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I have also heard 30 applications, without the pump coming on......
Could not be physically possible as the accumulator could only have about 25% by volume of compressed fluid.
I would buy into 5 presses however.
Can someone who has recently put in a brand new accumulator chime in with an observed brake pedal count?

In any event, coming on with every press as the OP said, is an indication of a soggy accumulator.
 

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1995-2002 Range Rover P38A
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Or not soggy depending on how you look at it. The 30 applications is the amount of fluid that can be stored in event of a pump failure so is the volume of fluid that can be kept under pressure, not the amount that can be used before the pump cuts in. That is a maximum amount too and assumes that all brake callipers, discs and pads are in perfect order. Wear or the slightest bit of run out on discs will cause the calliper pistons to withdraw further so a greater volume of fluid will be needed to apply the brakes too.
 

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OK, so for a "Normal everyday, average " Rig, how many presses till the pump runs?
I was aware it was not 30 till pump run, I was just attempting to quantify the situation as there are
some out there who think that it is 30 presses till the pump runs, or it is a bad bulb.
Hate to see folks buy parts that are not needed.......One press to run, however, is probably an accumulator.....
Oh, by soggy, I mean the area usually full of N2 is now mostly brake fluid, thus soggy....
 

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But the N2 is the squishy bit, the fluid doesn't compress so won't be soggy, but we are splitting hairs. On mine, with a new accumulator, the pump will run after about 5 presses of the pedal. At that point the stored pressure drops enough to cause the pressure switch to turn the pump on to top it up. The more fluid needed to apply the brakes and the less presses will be needed so if there is the slightest hint of any air in the system, more fluid will be needed to compress the air too so the pump will cut in sooner. Unlike a normal system, a bit of air doesn't cause the pedal to go soft, it causes a slight delay in the brakes being applied as the first flow of fluid is compressing the air in the system before it starts to move the pistons.
 

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LEGACY VENDOR
1995-2002 Range Rover P38A
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I get 2-3 presses out of mine. Accumulator was replaced with a brand new one approx 3 years ago.

However, I am sure I have an issue in my modulator block (I have a second hand one to fit at some point when I finally get around to having it off the road for long enough to do!) as I can bleed the master cylinder part of the modulator block and then get a nice firm, solid feeling of brakes - however give it a few weeks (which I have so far) and I end up getting a spongy feeling brake pedal. It still stops, and can stop pretty quickly when it needs to!

However the pedal does still feel spongy until the brakes are bled again - which is why I believe that I've got a slight internal leak in the modulator. If I apply light pressure to the brake pedal for a couple of seconds then I get the solid feeling back as I then continue to press harder for full braking action.

Not sure if that helps with a diagnosis - but that's my experience with braking... and I'm pretty sure my accumulator is still OK - it's done this since I bought it, both before and after replacing the accumulator.

Marty
 

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Thanks, guys.
I was just wanting to get more input on this as there is confusion and I did not want someone to buy a new accumulator if it is working as it should.
I also get 3-4 presses out of both of mine before the pump cycles.

To beat the dead horse further......If the N2 chamber is compromised by a bad diaphragm, the brake fluid will be on the N2
side of the accumulator as well as it's proper side, thus the Accumulator is "soggy" :dance: (So there!)
 

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1995-2002 Range Rover P38A
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To beat the dead horse further......If the N2 chamber is compromised by a bad diaphragm, the brake fluid will be on the N2
side of the accumulator as well as it's proper side, thus the Accumulator is "soggy" :dance: (So there!)
and to beat it even further...... Years ago I used to run big Citroens, I had 5 assorted DS's and a couple of CX's (I've never been into 'simple' cars!) and they all used a virtually identical accumulator to provide the springing for the suspension (accumulator sphere on the end of a thing looking like an old style bicycle tyre pump). The problem with them was never that the diaphragm split but the N2 would leak out over a period so you ended up with solid suspension. A specialist near me built a rig for refilling the N2 and was kept very busy doing it as Citroen would only sell a replacement sphere. Only very rarely would he find one with a damaged diaphragm and that was usually one where the car had been run for years with no N2 left. I suspect the accumulators on ours are much the same in as much as the N2 finds a way out over a period. If the diaphragm splits then the N2 has to go somewhere and would end up filling the braking system with a compressible gas so you'd need to keep bleeding it, not something I've ever seen mentioned. Which makes me think they fail when the N2 has managed to find it's way out so there is nothing to accumulate the pressure.

So it's no longer soggy, it's solid.....
 

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OK FINE!, but a "Solid Liquid"
Thus, kinda soggy by definition..........
So, on these accumulators, you have a seam where the 2 halves are put together, and a small nub on top, presumably where it is filled?
I have often wondered as well as to the destination of the missing N2.
I believe the rubber diaphragm becomes a bit porous as any rubber will over time. These things are run hot and hard in there....
I believe as the N2 escapes over years rather than a catastrophic event, and as it is injected into the system near the reservoir, that it bleeds off to atmosphere with the returned fluid after braking. This would be a very small volume of gas relative to the amount of brake fluid being pushed back and forth and since the fluid does not actually travel through the system, just back and forth, it would hang around the high point of the reservoir.
That's my theory, and I'm a stickin' with it!:thumb:
 

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Well, soggy vs. solid aside, now I'm paranoid and am going to have to go drive around in circles listening to the abs pump!

Just changed a caliper and went through the mind numbingly long bleed process. I'd hate to have to go through that again...
 

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Well, here is the cool thing!:
The accumulator is the simplest fix on a P-38!
Get the replacement, with engine, and key off, pump the brakes about 20 times, unscrew the old one, screw on the new one, and you are done! No bleeding required.
Driving in circles listening to the pump should be a fond memory........If it is the accumulator (Which is very likely)
 

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Good to know! I'll keep listening to the pump and figure if it needs attention or not. I figure if it lets me hit the brakes a few times before coming on, I'm in the clear. :)
 
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