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Joined: Feb 07 2020
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Soft pedal when car left for a few days. Fine after about 20 secs of running.

Cow moo noise almost every time I press the brake pedal (always done this to be fair)

Am I looking at the accumulator?

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Joined: Feb 11 2018
Posts: 407

The red dash light should go off after about 8 seconds when first starting.

If you hear the pump coming on every press of the pedal you have a problem. Probably accumulator.

When was system last serviced, I.e. new fluid, pads etc. More so when bled last. Air in system will also cause issues.

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Joined: Aug 05 2019
Posts: 128

Soft pedal after a few days is pretty normal. Pump should run for about 40 seconds on initial start up and then cut out. It should then run for maybe a second or two every 3 or 4 brake applications.

If it runs for only a few seconds on initial start up and runs for a brief period on every brake application, it is a sign that the accumulator is shot. It is a service part and pretty cheap really. The accumulator was fitted to a number of different cars, so you may find one that is listed for something else and a little cheaper if you search by the Wabco number.

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Joined: Mar 22 2016
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40 seconds on start up sounds like your brakes need bleeding, mine was like that till I bled them , now it’s around the 10 second mark.

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Joined: Aug 05 2019
Posts: 128

Noted

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Joined: Dec 30 2015
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40 seconds on startup isn't unusual - the system will bless down the pressure I've time, so if it's been sitting awhile, then 40s is about right for it to get up to pressure.

In your case though, the fact that the pump runs every press of the pedal shoes that the accumulator isn't working as it should and keeping the system with pressure in it. You should get 3-4 applications of the brake pedal before the pump runs again

If it's running all the time when you press the pedal is definitely time to replace the accumulator before it runs the pump too much, or cooks the abs relay in the fuse box.

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Joined: Feb 07 2020
Posts: 55

Slightly conflicted thoughts here for me then. First is that this has happened only 2 or 3 times and only recently. I've left the car for a month before and not had a soft brake pedal, but also had it running on position 2 (no engine) which also seems to prime the pump so maybe that was it.

I'll monitor it. I think it runs nearly every brake press.

Fluid and bleeding is about 12 months as did rear callipers after a bearing collapse melted things!

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Joined: Dec 30 2015
Posts: 1216

If the pump runs every brake press then the accumulator definitely needs replacing.

I had one that turned up here and the ABS relay was burning hot, and the abs pump not running at all. The ABS relay was cooked and when I loaned him a replacement so he could get home safely (which typically I've never seen again), the pump ran every press of the pedal.

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Joined: Feb 07 2020
Posts: 55

Thanks, I will monitor the situation.

Presumably it’s a vacuum storage device that develops a leak somewhere??

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Joined: Feb 07 2020
Posts: 55

Thanks, I will monitor the situation.

Presumably it’s a vacuum storage device that develops a leak somewhere??

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Joined: Dec 30 2015
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No, it's a globe with a diaphragm with Nitrogen under pressure on one side and brake fluid on the other. The pump builds up the pressure and the accumulator, as it's name suggests, stores it until needed. The brake pedal just opens a valve to let the high pressure fluid through.

Couldn't tell you exactly how long my pump runs for but probably around the 30-40 second mark and that is with an accumulator that was replaced about 4 years ago. All I know is the lights go out by the time I reach the bus stop down the road if I start the car first thing in the morning, reverse out onto the road and drive off. Pump cuts in after every 4 uses of the brake pedal.

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Joined: Aug 05 2019
Posts: 128

As noted above is it a pressure accumulator. What ever you do, follow the instructions in RAVE if you go to replace it. The accumulator should, if good, have a static pressure of 80 bar and the system pumps up to about 150 bar, so it needs to be depressurized before you play with it.

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Joined: Feb 07 2020
Posts: 55

Thanks all. Appreciate the advice.

Will locate the relay and see if it’s getting hot too...

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Joined: Dec 30 2015
Posts: 2016

The accumulator is a quick and easy fix, certainly less of a Big Deal than an ABS pump...

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Joined: Dec 29 2016
Posts: 447

The Vogue SE that I've just put the engine in needs a brake accumulator I think. If you park the car up for 24 hours, then jump in it, start it and move off straight away there's no brakes. Thankfully, moving straight away for us is going into reverse and turning around on the driveway but the first time it happened I did brick myself!

Going to order a new accumulator and a new radiator as the Eurospares one from Island 4x4 hasn't lasted 500 miles before it started to leak. There's no damage on it but when the cooling system is up to pressure it's leaking. Annoyingly, it's 1 month outside of it's 12 month warranty too.

David.

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Joined: Feb 07 2020
Posts: 55

dhallworth wrote:

The Vogue SE that I've just put the engine in needs a brake accumulator I think. If you park the car up for 24 hours, then jump in it, start it and move off straight away there's no brakes. Thankfully, moving straight away for us is going into reverse and turning around on the driveway but the first time it happened I did brick myself!

Going to order a new accumulator and a new radiator as the Eurospares one from Island 4x4 hasn't lasted 500 miles before it started to leak. There's no damage on it but when the cooling system is up to pressure it's leaking. Annoyingly, it's 1 month outside of it's 12 month warranty too.

David.

I'd be interested to know if this fixes it David.

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If there's no brakes at all, the hydraulic circuit has air in it so is doing nothing until the power circuit is up to pressure. Hydraulic on their own are a bit pants but will stop the car, eventually, if you use both feet on the pedal..... I had the ABS pump burn itself out a few years ago so had to get home on hydraulic only. Think conventional brakes but with the servo not working.

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Joined: Feb 07 2020
Posts: 55

Changing the accumulator worked a treat.

Followed RAVE but still got brake fluid squirting out when unscrewed it. Not a great deal but under a bit of pressure...

Was a bit of a cow to get to as the LPG was installed all around it. Ended up unbolting the fuse box, lifting out of the way and getting a spanner underneath to crack the seal a bit. Then could remove by hand. Nipped new one up in the same way. Longest part was clearing up the brake fluid as it cover the airspring and travelled along the chassis dripping!!!