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I had the fun experience of having a minor brake failure, I say minor because I still had a small amount of my brakes, last week. Thank goodness it was early in the morning and in town but was quite scary nonetheless. By the way if you get the low brake fluid warning, pull over immediately as you will still have brakes for a few uses before they are completely gone. When I got it stopped and opened the hood there was brake fluid all around the accumulator and the drivers side of the engine bay. I tracked it down to the oring on the brake accumulator, which I replaced 3 months ago. I was able to get a replacement oring from an auto parts store and drive it home and then promptly ordered the correct oring from Atlantic British.

Now I am trying to figure out if when I installed the accumulator if I didn't tighten it down enough, I followed the hand tight and then use an oil filter wrench to snug it down a bit more, or if the oring that was provided with the new accumulator just failed. Has this ever happened to anyone or does anyone have any suggestions to ensure this won't happen again? My plan was to let some loctite dry on the treads of the accumulator and then reinstall and use a thin wrench to tighten it down. I have never had a brake issues like this before and I have done brake jobs on all my cars so I felt comfortable with my skill level doing the job. Any opinions or feedback would be greatly appreciated because this cant happen again and I feel very lucky it was just me in the car not my wife or son and I was able to resolve the situation without incident.

Thanks,
David
 

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2002-2005 Range Rover MkIII / L322
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Scary! Yours is the first I've heard of.
 

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if you lubed the o-ring before installing accumulator then possibility of defective ring or fault in accumulator where o-ring sits. O-ring works without requirement of excessive tightening. How long did you have leaking before failure?
 

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Discussion Starter #4
I installed the accumulator in mid February and did use brake fluid to lube the oring on install. I didn't notice any leaking prior to the failure and it seems like I just woke up one morning and the oring decided to go out. My concern what steps I should take to make sure this doesn't happen again in the future. Do you think using loctite on the threads and then a wrench on the accumulator is a good idea? When I removed the failed oring it looked like someone took a razor to one side of the oring and cut it in a similar pattern as the threads, I wish I took a picture of it for future reference.
 

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1995-2002 Range Rover P38A
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laszlost said:
When I removed the failed oring it looked like someone took a razor to one side of the oring and cut it in a similar pattern as the threads, I wish I took a picture of it for future reference.

May be wrong but here goes.

Its possible that you placed the O ring on the pump instead of rolling it down all the way to the ball side of the thread of the accumalator, if you did roll it on thens its possible it rolled a few threads back down while you were turning the bomb back on
 

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Discussion Starter #6
I was exceptionally careful follow the instructions and did place the oring on the accumulator before installing it. Is there such thing as having the accumulator to tight?
 

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If you over-tighten it, you could damage the o-ring. It's not metal; it could crack or tear easier. I'd say the wrench was overkill. I just hand-tightened it on both of our Rovers, which have been fine for almost 3 years. Check the accumulator and the pump housing for sharp burs. When you install the o-ring on the accumulator, make sure to twist and turn it in a way to remove the preload and its tendency to roll off the seat.
 

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It would be very hard to even speculate as to the cause of your o-ring's demise.

One thing I know: o-rings are not just o-rings.

Check these out:
http://www.rlhudson.com/O-Ring%20Book/opening.html
http://www.marcorubber.com/materialguide.htm
http://www.epm.com/material_guide.htm
Those are just a few examples.

I just Googled: o ring failure analysis
What it came back with:
About 1,590,000 results (0.34 seconds)
Here's one of them:
http://www.rlhudson.com/O-Ring%20Book/d ... g-div.html

Some good photos might be helpful - to see if anyone notices anything unusual.

Unless it recurs, the world may never know. Out of every 5,000 little purple o rings manufactured, at least a few are bound to be flawed. The wrong o ring in the wrong place at the wrong time.
 
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