Rsvl-Rider

ABS accumulator ball testing when uninstalled?

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I'm wondering if there is a way to test an ABS accumulator ball without power, or outside of the car. I have seen a couple in the junk yard but I obviously have no way to test them there. And I'm not sure of how they fail. Is it all or nothing, like a popped ballon, or something more gradual or subtle? 

 

I've thought about some sort of hand pump. I realize it won't apply the high pressure required but it would be an obvious fail if it failed to hold any pressure at all, right? 

 

Alternatively, is there a procedure for a simple "garage" check?  Maybe using common tools or a compressor or some such? 

 

I could test it by swapping in and out of my daughter's 1990 coupe I guess, but I prefer not to use it as a test bed. I don't want to mess with something that is not broken.

 

Thanks

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32 minutes ago, Rsvl-Rider said:

I'm wondering if there is a way to test an ABS accumulator ball without power, or outside of the car. I have seen a couple in the junk yard but I obviously have no way to test them there. And I'm not sure of how they fail. Is it all or nothing, like a popped ballon, or something more gradual or subtle? 

 

I've thought about some sort of hand pump. I realize it won't apply the high pressure required but it would be an obvious fail if it failed to hold any pressure at all, right? 

 

Alternatively, is there a procedure for a simple "garage" check?  Maybe using common tools or a compressor or some such? 

 

I could test it by swapping in and out of my daughter's 1990 coupe I guess, but I prefer not to use it as a test bed. I don't want to mess with something that is not broken.

 

Thanks

 

Unless you're a skilled machinist I strongly recommend against building something in the garage and trying this at home. Yes, if it fails to hold any pressure at all it would obviously be bad, but it needs to hold a couple thousand pounds of pressure to work as needed. Also recommend against needlessly removing a working accumulator from a working system, after the bladder has been stretched when compressed enough times, draining them down to zero fluid pressure can rupture the bladder.  

 

An accumulator is kind of like the fluid filled version of a NiCad battery, just so many years or so many charges and it won't hold a charge anymore. So it's a little more than how much pressure will it hold, it's also how long will it hold pressure.

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Actually any accumulator, good or bad, would hold pressure unless the metal sphere has a hole in it. What determines if an accumulator is good or bad is how much pre-charge gas pressure (about 1000 psi) is on the backside of the bladder trying to push brake fluid out of the accumulator. The pre-charge pressure pushing against the brake fluid is what gives you the reserve pressure you need when the pump isn't running. If the bladder ruptures, or the pre- charge leaks out someway, you won't have the reserve pressure and therefore the accumulator is considered to be bad.

 

I haven't tired this, and I'm not recommending this, but I think I've read that if you insert a small blunt rod into the hole in the fitting on the accumulator that it can easily be pushed deep into the accumulator if the bladder is ruptured. Otherwise if the accumulator is good the rod will only go a short distance into the accumulator until it touches the bladder that has pressure behind it. The pressure in the bladder keeps the bladder from moving back preventing the rod from going in deeper.

 

I have an old accumulator around here somewhere but I've not been able to find it this morning. If someone has a bad accumulator please do the test with a small rod and see what you find. If this test pans out it would be a good way to screen out bad accumulators at the salvage yard. It wouldn't tell you if the accumulator was weak but it would tell you of the bladder was ruptured and not worth testing on you car..

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I just went out and "tested" 7 used accumulators on the shelf with a plastic alignment tool from my TV repair days.

The tool went in 7/8" in 6 units, and 3 I/2" in one unit.

I have a brand new one I was going to test, but it's still sealed in its package and I didn't want to 'disturb' it.

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56 minutes ago, harry yarnell said:

I just went out and "tested" 7 used accumulators on the shelf with a plastic alignment tool from my TV repair days.

The tool went in 7/8" in 6 units, and 3 I/2" in one unit.

I have a brand new one I was going to test, but it's still sealed in its package and I didn't want to 'disturb' it.

 

While you were making your post I was out testing my old accumulator. It was bad when I got my Reatta. I got exactly the same result as you. The rod whet in 3-1/2". I think that is a good field test if you were trying to cull bad accumulators in a salvage yard. If the rod only goes in 7/8" you know that it has some pre-charge left and would be worth trying on your car to see if it is really good.

 

I took a couple of photos. I might add this test to ROJ unless someone comes up with a better test to screen used accumulators.

 

SAM_3487.JPG

 

SAM_3488.JPG

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Great idea Ronnie!

 

I think Harry's results show a quick benchmark that can easily be used in the field. I just measured two that I obtained in the junk yard. One went in 1" and the other went the full 3 1/2" as Harry's did. Also, the one that went 3 1/2" also had quite a bit of residual fluid remaining inside. I recall there was brake fluid in the system when I removed this one. For that reason I left it upside down to drain it all out. When I retrieved it to do the measurement a considerable amount of addition fluid leaked out. I think this supports the idea that the deep insertion indicates a ruptured bladder which had become filled with fluid.

 

It might not prove that the ball is good, but should certainly prove when it is bad...

 

Good work Harry! 

 

This is exactly what I had in mind. A quick go - no go test to do in the field.

 

Thanks Guys!

 

Edited by Rsvl-Rider
added info (see edit history)
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6 minutes ago, Rsvl-Rider said:

the one that went 3 1/2" also had quite a bit of residual fluid remaining inside. I recall there was brake fluid in the system when I removed this one. For that reason I left it upside down to drain it all out.

 

When I replaced mine years ago I remember mine having a lot of fluid inside it because it made a mess on the workbench. It makes sense because the bladder being ruptured has no pressure behind it to push the fluid out and no vent to allow it to easily gravity feed out. I've removed my good accumulator (after pressing the brake pedal 25 times to relieve the pressure) and very little fluid came out. I guess excess fluid remaining in the accumulator when it is removed is another tell-tale sign that the accumulator is bad.

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The results of this simple test makes good sense..I would wonder if shelf life would not be a big factor if the main stress would be the amount of use on the blader. A new un used accumulator should have a long shelf life which is good news

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The probe test only show bad accumulators.........really bad ones

In the picture below, the left accumulator is charged, pushing the bladder against the inlet port.

A good new accumulator is precharged with 750-1200 psi (depending on the source you read)  none of us could deflect the bladder if it had 750 psi behind it, so there would be no deflection.

So depending on how hard you can push, the precharge in anything you can deflect is probably less than 200 psi.

The other thing that bothers me about using a probe is the chance of damaging the bladder in a good accumulator.

 

Ronnie said he had one that leaked out fluid.... note that a unit with almost any precharge will push the bladder down against the walls and there will be little or no room for fluid...hence very little leaks out.

However if the bladder has failed and fluid get on the precharge side of the bladder, the accumulator could be full of fluid.   Also a unit with the precharge completely depleted, the bladder would be deflected by the incoming pressure and some amount of fluid would be in the accumulator.....this accumulator would be so bad the brakes would have failed a long time ago.

3 ACCUMULATORS BIG.jpg

Edited by Barney Eaton (see edit history)

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2 hours ago, Barney Eaton said:

The other thing that bothers me about using a probe is the chance of damaging the bladder in a good accumulator.

2 hours ago, Barney Eaton said:

However if the bladder has failed and fluid get on the precharge side of the bladder, the accumulator could be full of fluid.   Also a unit with the precharge completely depleted, the bladder would be deflected by the incoming pressure and some amount of fluid would be in the accumulator....

 

I have only tested my old accumulator that I know for sure was bad so other accumulators may fail in a different manor. There was no pushing the bladder back to get the rod to go in 3-1/2" so there is no danger at all of damaging the bladder. The rod literally fell into the hole without any pushing. The bladder must have been in the position shown in your third drawing and the cavity was completely full of fluid when I removed it from the car. The accumulator had been off the car for about 7 years so I guess the bladder must turn inside out (like a toilet plunger does) and remain in that position once the bladder ruptures.

 

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The tester has been discussed before, so I put together a basic idea of what I think it needs and why.

This tester would allow you to test the pressure switch, and the accumulator.....experience would tell you how good the pump was.

It would be wired the same as in the car, once the MAIN switch was on, the pump would start and build pressure until the pressure switch turned off the motor.

At that time you would know the high TURN-OFF pressure.....a stop watch could also be used to see how long different combinations take to get to the turn off pressure.

The PRESSURE RELEASE VALVE would be cracked open....the 2500 psi  would go into the graduated reservoir.....at this point you would be watching the gage pressure drop until the pressure switch turn on the pump motor.

At this point you would know the high and low limits of the pressure switch.

The other thing you are watching is the graduated reservoir.....this will tell you how much fluid the accumulator is holding.

You would start (ideally) with a new accumulator....this new unit would hold the least amount of fluid (because it has a full pre-charge)

You could get a fancy with the control panel as you like... ON-OFF switch is basic to cut power to everything, some relays and reset switch would cut power when the pressure switch turned the motor power on and off...this would all you to see exact

pressure.

You could also hold the unit at high pressure and check how fast it "leaked down"  this would help evaluate the condition of the pump and check valve.

Lets see who can be the first to build one.

tester.jpg

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I knew the rod test was probably going to be too simple so I decided to go with a hydraulic tester as was suggested. As you can see I had to add a few additional items to the original plan to bring it up to OSHA standards.

 

As soon as I get some wheels and a trailer hitch installed to make the tester portable, I'm going to hook it behind my Blazer and pull it out to the junk yard and see if I can find a used accumulator to test.. This is going to save a lot of time over having to screw the accumulator into the master cylinder on my car to test it. :D

 

 

accumulator tester..jpg

Edited by Ronnie (see edit history)
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What a great idea, it appears it would have enough capacity to test several at one time.

While you did not mention it, if you could get it powered by Bull S__T it would also be an energy saver.

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Is there a source for these accumulators, either NOS or rebuilt? I have a Lincoln Mark VII that uses the same system (Teves) and I believe the accumulator has gone bad. Every time I apply the pedal, the brake/ABS light flickers for a moment, then stabilizes and the Google says that's a sign of a bad accumulator. So I'm looking for a good replacement.


Any ideas where to look besides a junkyard?

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1 hour ago, Matt Harwood said:

Is there a source for these accumulators, either NOS or rebuilt? I have a Lincoln Mark VII that uses the same system (Teves) and I believe the accumulator has gone bad. Every time I apply the pedal, the brake/ABS light flickers for a moment, then stabilizes and the Google says that's a sign of a bad accumulator. So I'm looking for a good replacement.


Any ideas where to look besides a junkyard?

 

Google for best price under Range Rover part # stc 2784, will work just fine in Super Coups and the Mk 7

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30 minutes ago, Digger914 said:

 

Google for best price under Range Rover part # stc 2784, will work just fine in Super Coups and the Mk 7

 

Awesome! Thank you!

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The Range Rover part # stc 2784 accumulator is a Wabco. I've not saw anywhere that anyone has reported successfully useing one of these accumulators on a Reatta. If someone tries one of these please give us feedback about how it fits and performs. It looks awfully tall to me.

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16 minutes ago, Ronnie said:

The Range Rover part # stc 2784 accumulator is a Wabco. I've not saw anywhere that anyone has reported successfully useing one of these accumulators on a Reatta. If someone tries one of these please give us feedback about how it fits and performs. It looks awfully tall to me.

 

A few months back and I don't remember how many had a guy here that saved some money and got a compatible with wabco that is considerably larger and made it fit, after that I posted a pic of the wabco side by side with the delco. The wabco is actually a hair smaller than the accumulator that spinning wheels sells when they have them in stock.

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Yeah, I guess I made a mistake assuming we were talking about a Reatta. With that in mind I wonder why Spinning Wheels, who specialize in Super Coupes with the Teves Mark II brake system, would special order accumulators if the Range Rover part # stc 2784 Wabco would work on them since it is readily available at a reasonable price? Can anyone offer first hand knowledge that the Wabco will work on the Teves Mark II system?

 

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1 hour ago, 89RedDarkGrey said:

 

 

 

It seems our wires are crossed? Is Matt looking for a Lincoln or Reatta part?

 

Matt is looking for a part for a Mark VII Lincoln and except for where you grab with a wrench the Wabco accumulator is a near perfect in all specs to the OE Ford part which was made by ATE. The Ford guy's started substituting the Delco part partially because their part was hard to get and partially because the GM 255 part number cost considerably less. GM used the exact same ATE part on the Saab with a different part number at several times the 255 part number price. The SuperCoup group had no trouble using the ATE accumulator with the GM 255 part number which held less fluid because pressures and fittings were the same.  

 

Ronnie is wondering about using the Wabco on a Reatta and why Spinning Wheels isn't selling them. My guess is that Spinning Wheels gets a better price on the Hydac. and they are in business to make money.

 

Both the Hydac and Wabco accumulators are similar in shape and hold a couple more ounces of brake fluid than the ATE accumulator that GM sold under the 255 part number and because they are both flatter and fatter up top that the ATE accumulator, they are a tight fit on the Reatta, and you will need to pull the cross brace loose to get them in and out. Looking at the picture our accumulator on the right looks bigger than the Wabco on the left because it's sitting on the allen wrench fitting which adds about a half an inch to height, but the Reatta doesn't care about that little bit of extra height in the center.

 

 

Accumulator size WABCO to ATE.jpg

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If the supply of these accumulators is running dry, a small,  say 1 quart accumulator with some fabbed fittings could be remote mounted with high pressure stainless tubing.

the ones we use in our hydraulic systems have replaceable bladders and Schrader  valves where they can be repressurized .

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