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Is my accumulator bad?


DAVES89

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I think it is a great idea and it is great that you have undertaken this project. I appreciate the effort you have put into this so far. I look forward to the results of your future tests but I realize this is a busy time of year. I usually save projects like that for winter. This time of year I drive my car as much as possible. This weekend was ruined by rain. Maybe next weekend...

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Just a quick interesting experience. I finally got a chance to take a fast run to my cottage today, and that gave me the chance to grab the accumulator from the '89. It has been sitting cocooned up on blocks for over two years. I went to unscrew the accumulator and found a considerable amount of pressure still in the system. I never dreamed there would be any residual pressure after all this time, but there certainly was, and was treated to a strong spray from the relief hole just as the o-ring decompressed. Needless to say, I would have been even more upset with myself if I had sprayed fluid under the hood on my better car which has been treated much more gently, except for the turbo abuse :)

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Sounds like your best Teves system might be on your '89. I wouldn't have expected any pressure to be in there after that amount of time for sure.

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Frankly, I was shocked. I believe that whole pump/switch/accumulator setup is the junkyard setup Dave helped me procure. AZ Ron is sending his Spinning Wheels accumulator to me unless it gets sold in the next day and I may have my car home shortly so I will have at least two and maybe three more to test. More is better to see a good pattern. I forgot to get a cross sectional area for the reservoir when I was under the hood, just to get an estimate of the fluid drop, which is about 12 cubic inches for 200ml and just over 8 ci.in. for 135.

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If I remember correctly the reservoir might be slightly tapered from top to bottom which might cause a problem with linear measurements of fluid drop from top to bottom.

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If I remember correctly the reservoir might be slightly tapered from top to bottom which might cause a problem with linear measurements of fluid drop from top to bottom.

 

10-4. I reckoned any fluid level tests would need to be done from the exact same place, right on the full level, to assure consistency and a point everyone can use to gauge the state of the accumulator.

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Well I'm stumped as to why I only get two pedal pumps before my pump starts after the system has been fully charged. When I installed the "like new" accumulator sent me to test on my car I only get three pumps. Dave tested the brakes on his Black car and he gets 8 pumps before his pump starts.

 

I got to thinking that the pressure switch is what actually tells the pump to run so, I removed the one from my spare master cylinder and tried the test again. The result was the same as before. I got only  2 pedal pumps and the pump starts to run.

 

As a last straw I decided to take the accumulator off my spare master cylinder and try it. When I started unscrewing it fluid started pouring out of it. A lot of fluid poured out. I stuck a rod up inside that accumulator and I found that the rod easily went all the way in indicating a ruptured bladder.

 

I really don't know what to do next. I doubt both pressure switches are bad and I don't think Dave's accumulator or my original accumulator is bad. So what else could be causing the pump to start up in tow pumps of the pedal?

 

If someone else would try this on your car it would be appreciated.

 

-Turn the key to on.

-Let the warning lights go out and listen for the pump to stop.

-Then with the key still on start pumping the brake pedal in a normal fashion until you hear the pump start again.

 

How many pumps of the brake pedal did you get before the brake pump started?

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Ronnie, this is the same issue I have struggled with. What counts as a standard pump? I can't get more than 2.5 "pumps" no matter what accumulator I use and I know my working pressures are spot on. The only possibilities I can come up with are the pistons in the calipers perhaps retracting further than normal, or are the brake hoses expanding? It is a wide disparity so I am at a loss on what your experience is.

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I took the car for a drive today and gave my brakes a good road test for how it would stop. The brakes feel solid and it will stop on a dime without a problem. The ABS seems to work as expected if you get on the brakes really hard. No lights under hard stopping or otherwise.

 

I tried the road test with Dave's Hydac accumulator he sent to me and then I put my old accumulator back on and did the same tests. I couldn't tell a difference between them when driving normally or stopping hard. My only concern is is the brake pump starting so quickly when you give the pedal a couple of pumps. I don't know anything else to do so I guess I will have to get use to it and cross my fingers that it won't hurt the pump/motor,

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Ronnie, is this the standard size Hydac? I imagine so since it isn't a quick swap with the larger one from Spinning Wheels. This sounds much like the same experience I had, swapped in a new standard accumulator and found little, if any difference. It is perplexing. If my testing is accurate, there is about 33cc's contained in the working range of a newer accumulator. Two pumps would mean about 15cc per pump, but Dave's experience indicates about 4cc per pump?? I think Kdirk was looking into refreshing the pump motor but haven't seen any progress or resolution.

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I think it is the standard Hydac like Spinning Wheels sells. It came from Marck at ECReattas but I'm sure they are one in the same. Below are the results of  my tests and Daves. Changing the pressure switch made no difference in the testing Let me know what you think.

 

KEY ON

Seconds until red warning light goes off - Mine=30 - Hydac=38  - Dave's Black car=35

Seconds until pump motor shuts off - Mine=46 - Hydac=59  - Dave's Blackcar= 54

 

Pumps until pump motor starts again - Mine=2 - Hydac=3  - Dave's Black car=8

Pumps until red light comes on again - Mine=12 - Hydac=14 - Dave's Black car=16

 

KEY OFF

Pumps until pedal gets hard - Mine=12 - Hydac=15 Dave's Black car= 14

 

I can understand the pump running longer to turn off the red light and the pump shutting off with the Hydac. I think that is because your new accumulator is bigger. I was expecting the new Hydac accumulator to give me more pumps before the motor started running again but only got one more pump.

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To be clear, the Hydac is physically larger? It should have the rating on the side somewhere, I thought it is something like .33 liter. A standard accumulator can be changed without removing the cross bar and the large Hydac will hit the bottom of the bar and it must be shimmed up. If this is the larger Hydac, your experience mimics mine, there was only a small change in reserve capacity.

 

It is hard to get a firm handle on the run time comparison because the supply voltage and other factors are unknown. Since there were two tested on your vehicle, it looks like the Hydac has greater capacity all the way down the line. It is harder to equate yours and Dave's as I mentioned except the run time after red light out is 16 for yours and 19 for Dave's, which is more similar than it looks at first. The fly in the ointment is the red light operates from a different set of contacts and is something I can't test for at this time. It may be possible there may be a difference in the set point even if the pump operates in the correct limits. I need to get a better handle on the light relationship to actual pressure. I know the difference is only one pump for the Hydac but that is a 50% increase.

 

If we compare Dave's and yours, and assume they are on the same car:

 

My testing of the estimated light out pressure of 1500psi would indicate yours trips earlier, which indicates a greater pre-charge since it does so using less volume. I can't judge the run time to full charge because I didn't test for that, but the 16 sec for yours vs 19 sec for Dave's seems to follow the pattern that smaller volume = less run time, so again yours may be better.

 

Now if we consider the number of pumps:

Yours take six times as many to trip the light as start the pump (difference of 10), Dave's takes twice as many (difference of 8), so there is something very different, but I don't know if that is the "pump" or the light set point or something else??

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As you can see in the photos below, the Hydac is physically larger by quite a bit. It has 2 C.I. written on the side which equates to .33 liters. It is identical to the one AZ Ron has for sale. Dimensions are approx. 3-5/8 dia. x 3-11/16 high.

 

Quote

Now if we consider the number of pumps:

 

Yours take six times as many to trip the light as start the pump (difference of 10), Dave's takes twice as many (difference of 8), so there is something very different, but I don't know if that is the "pump" or the light set point or something else??

 

There does have to be something different.  Doesn't seem like the voltage should make a difference in the number of pumps before the pump starts because at that point the pump has stopped and the motor is out of play and the accumulator should be fully charged to provide the maximum reserve pressure. It might make a difference in how long it takes to charge the accumulator but once the pump stops the pressure should be at the pressure determined by the cutoff point of the pressure switch. 

 

Even though the pressure switch controls when the pump starts, I don't think in my case that is the problem. When I installed my spare it made not difference in the number of pumps before the pump started. I think chances are slim that I have two pressure switches that are out of spec by identical amounts. However, knowing that I have a good accumulator installed (Dave's Hydac),  logic and experience with hydraulic systems tells me the problem is with the pressure switch(es) having a low pump cut-in pressure.

 

You peaked my interest when you said the ACDelco accumulator should come off with the crossbar in place. Mine won't because it has a pin that sticks up preventing it from coming out from under the crossbar. I had to raise the crossbar about 3/4 to 1 inch to get enough room to clear the pin. You can see the pin in the photo. Do all the pumps have that pin sticking up? I wonder if Dave's pump has that pin?

 

I really wish someone else would do the test below and post your results. That  might give a better picture of how the average Reatta brake system performs.

 


KEY ON

Seconds until red warning light goes off - Mine=30 - Hydac=38  - Dave's Black car=35

Seconds until pump motor shuts off - Mine=46 - Hydac=59  - Dave's Blackcar= 54

 

Pumps until pump motor starts again - Mine=2 - Hydac=3  - Dave's Black car=8

Pumps until red light comes on again - Mine=12 - Hydac=14 - Dave's Black car=16

 

KEY OFF

Pumps until pedal gets hard - Mine=12 - Hydac=15 Dave's Black car= 14

 


 

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They all have the vertical tube that sticks up. It is a very tight fit and some wiggling to get the stock ball off with the brace in place. It is far easier to remove or loosen the one end and pull it up a bit. I see you have the larger ball and as I said before, your experience is the same as mine; it helps the reserve but does not bring it up to the commonly accepted standard?? The best way to know for sure on the pressures is to fabricate a test setup and run it. I would lend you mine but I am in the midst of doing my own testing. I need to find the pressure switch pinout to check where the red light turns on and off to connect a test light. I am pretty sure they are at different set points, like 1500 off and 1200/1300 on. I have been meaning to get the FSM out and read through it again.

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I've been putting a lot of thought into what could be the difference between Dave's brake system and mine that could cause him to get more pedal pumps if we both have good accumulators and we both have good (equal) pressure switches. I think I might know the answer but I'm not sure what is causing it.

 

Let's assume that Dave and I have motors, pumps, accumulators and pressure switches that are equal. Also assume that both of our systems have the same accumulator pre-charge and the pump cuts off at the same pressure. Now, with that in mind, what would cause my pump to start sooner? I think it is the volume of fluid that is drained out of the accumulator with each pedal pump. If I drain out more fluid with each pedal pump it will reduce the pressure in the accumulator quicker which would turn on the pump with less pumps of the pedal. That is why the larger volume of the Hydac accumulator gives me one more pedal pump than my smaller ACDelco accumulator. What do you think of that theory?

 

If I'm right in my explanation, what is causing my system to drain more fluid out of the accumulator with each pump of the pedal?

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Ronnie, this was my conjecture as well. I theorized up above about some things I was thinking about: brake hose(s) expanding under pressure, calipers retracting further than normal or perhaps air in the system? I have experienced caliper kickback on my Ford Ranger when a front wheel bearing was getting loose but that wouldn't happen sitting still?? Perplexing. I can perhaps shed a little light on the Hydac vs standard style accumulator results. Thanks to AZ Ron, I have his large Hydac in my possession and I tested it today. I also tested the well used one from my '89 which I will call accumulator "D".

 

psi 1500 2000 2600 3050 Pre Charge

 

D -> 170cc 190 200 210 425#

 

Hydac 107 155 192 205 925#

 

My accumulator "D" is a dead ringer for "A" which I tested previously. The Hydac clearly has much better capacity however, when the capacity in the working range is compared to my best standard style ©, the difference is fairly small, 37cc vs 33cc, only about a 12% increase. I was concerned that my second setup had an error built in so I reran "C" again and the results were very consistent with the first session. Since the gauge is only in the 20% range when looking at the pre-charge, the accuracy may not be as good as mid-scale, but it was clear the best accumulator "C" was over 1000# and the Hydac was under, as near as I could tell, a difference of 100psi or about 10%. If that is consistent with the one you have, it explains the small increase inn reserve.

 

I intend to get a couple quarts of fresh brake fluid and run all of them again because the fluid appears to get somewhat aeriated from the repeated pressurize and dump cycles and is becoming less transparent.

 

I am going to consider changing the brake hoses, just because, and it's time for a flush anyway.

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I hope you find what is causing it. If it's the hoses I will change mine. I'm wondering if it might be the piston adjusters in the rear calipers that might not be working causing excessive travel that would require more fluid before the pad makes contact with the rotors.

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10-4 and I would welcome your input as well. I do exercise my parking brake occasionally and it seems to be in about the correct range. By the way, the link 89RDG posted on the AACA has the front hoses on closeout, but no rears, although the price isn't that high to begin with.

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I have already replaced the front hoses on both the Red and Black Reattas. The verts front hoses have not been replaced [at least by me].

The Black has the original equipment rear calipers, and the Red has been changed to the Cadillac calipers. If you guys want me to run another test the only two I should run would be the 'vert and the Black not the Red. All three cars have the original AC Delco accumulator balls [although I am quite sure they are not the original ones].

The 'vert is still in storage and may come out this weekend. I will do another test on the Black to confirm my numbers. I was in a bit of a hurry to get to the work on the Red so I want to be sure. When I get the 'vert out I will do that as well.

You could be on the right path with the hoses needing replacement as if they are starting to go bad would that not require the pump to work harder to get the fluid through?

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