ABS Failure (wear out after 9 years)

[glenncof]

1991 Range Rover (Classic) with 135K miles

This was tricky since it involved two components with inter-related failure.

First, the relay controlling the ABS pump stuck “on”. Since this ABS circuit is not controlled by the ignition switch the pump runs and runs. (Wife called and said there was animal under hood.) It is located under driver seat with a 30A fuse for the circuit. Replaced it and thought I was done.

Second, the ABS Accumulator had gone bad. My manual says to replace it every 5 years (I ignored this as I didn’t know what was.) and my RR had 9 years on it.

The Accumulator is a high pressure steel ball with a nitrogen filled bladder. The ABS pump builds pressure in the bladder which provides the power assist to the master cylinder. Feels like ‘almost like’ no brakes when system fails.

The nitrogen in the Bladder leaks out over time so it can’t hold much pressure. This will cause fast cycling of the relay (this accelerated the relay failure above) and eventually the pump stayed intermittently “on” since it can not build sufficient pressure to trip the shut-off pressure sensor. Seems worse in cold weather. Pump gets very noisy (dry running?) and hot.

At the time I was using a British repair shop. They burnt out 3 new ABS pumps (finding metal particles) and tried replacing the master cylinder/bleeding whole system. Finally they gave up so I had them put in the old pump and did my homework to fix it myself.

Caution: This Bladder is very high pressure brake fluid when pumped. Pressure can be relived by pumping brake peddle. I remember it required a bleeding operation before connecting it, with bleed hose just turn on ignition for very short time. It was gradual, not high volume.

Normal operation; Turn on ignition and a werrring can be heard under hood. Red “Brake” light on dash is illuminated (just like when parking brake is set). Once the pressure reaches the set point on sensor; pump goes off and light goes out.

If brake pedal is repeatedly pushed you can here the pump start again and shut off.

MY ABS light doesn't work (always on since 63K) so no help here.

I see www.AtlanticBritish.com sells ABS Accumulator for $249. My records show $262 which would have included shipping.

I have added 34K miles without a problem.

[nicyo]

Hi there, have similar problem with ABS & ETC lights continuously on, was wondering if anybody else had this problem and how to remedy this as it failed on the fitness inspection.

[OkieRover]

What the hell happened this weekend?
Mine came on too. I was just about to post about it.

So the repair is to replace this accumulator?

[OkieRover]

As JagGuy explained to me last night. When you turn on your truck the pump runs for a bit. Then when you press on the petal if the pump starts back up again on the first or second press your accumulator is toast.
So another great invention gone to pasture. He also said most brake systems have a back up if a part fails....you guessed it....this one doesn't have any back up.

[troverman]

If your ABS & ETC lights are on (what model Rover?) than the problem is most likely either a junk or misaligned ABS sensor. I kept getting this "ABS Fault" and "Traction Failure" message on my 4.0. It turned out some wiring had broke between the rear sensor and the computer. I took the pass rear sensor out of the axle and pulled the whole harness down to repair. Put it all back in, good sometimes, other times you get the same message. The reason is, once you pull the sensor out of the boot, you have to replace the rubber boot for proper realignment.

[OkieRover]

I was hoping it was something easy. I'll check it. Thanks.