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Brake Flush Questions


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2 hours ago, Philbo said:

thanks 2seater.  I bought the Hydac new.  Do they age sitting on the shelf or only with use? Either way my brakes seem to be working pretty well so not worried about it.

Many have wondered about the shelf life and how to determine the date code for date of manufacture but no clear picture has been determined. There is no exact way to determine condition but we have developed several tests which give a fair idea of the condition, fluid drop being one of them. I made a test rig a few years ago with a pressure gauge to test pumps, pressure switches and accumulators and allows me to assign a number to the pre charge in the ball but it is an approximation and the fluid drop and pedal pump measurements work pretty well without any hardware. 

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I need to do test number 1 again from the how to, but un test 2 I get two solid brake pumps before the pump kicks on again. sometimes 2.5.  I only got 1 pump every time with the old one. so it's at least an improvement.  I've thought about trying to rig up an led on the dash that shows when the pump kicks on, so I can get an idea of how often it cycles and for how long.  After sitting over night it takes 30 - 45 seconds to fully charge the accumulator.

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2 hours ago, Philbo said:

I need to do test number 1 again from the how to, but un test 2 I get two solid brake pumps before the pump kicks on again. sometimes 2.5.  I only got 1 pump every time with the old one. so it's at least an improvement.  I've thought about trying to rig up an led on the dash that shows when the pump kicks on, so I can get an idea of how often it cycles and for how long.  After sitting over night it takes 30 - 45 seconds to fully charge the accumulator.

The pump charging time sounds pretty normal and the large accumulator from completely empty to full can approach one minute.I do not get the same number of pumps as some others so what qualifies as a "pump" is probably subjective enough to not be an exact science, but it is useful to keep a personal record over time. I think the led lights on the pump are an interesting idea. It would certainly give a real life view of pump cycling in actual conditions and I may just steal that idea, at least for a test session. I consciously try to maintain brake pedal pressure as I am slowing down rather than an initial application and then a 2nd or 3rd, as is my habit from old school brake systems, in the belief that the pump will run less often. The indicator would tell the tale about that.😎

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Just take off one of the mounting insulators for the pump/motor and you will have a great idea how often the motor runs. I swapped a pump/motor one time and omitted one insulator. I was surprised at how often these pump/motors run. It is surprising to me how long they last, but still a good reason to have 3-4 back ups...

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1 hour ago, 2seater said:

I consciously try to maintain brake pedal pressure as I am slowing down rather than an initial application and then a 2nd or 3rd, as is my habit from old school brake systems, in the belief that the pump will run less often.

I do the same thing. Once I lay my foot on the brake pedal I try to get slowed down as much as needed without having to pump the pedal again.  It might be a little harder on brake pads but I think it might keep the pump from running excessively. Having a small led mounted in an inconspicuous place might be a good idea.

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3 hours ago, DAVES89 said:

It is surprising to me how long they last, but still a good reason to have 3-4 back ups...

I need to procure myself a backup.  On a side note, I've heard the 91 model year used a standard vacuum boosted setup.  Is that true?  If so are parts for those hard to come by and is there any reason why you couldn't replace the Teves mk II with that if it died?

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5 hours ago, 2seater said:

I think the led lights on the pump are an interesting idea. It would certainly give a real life view of pump cycling in actual conditions and I may just steal that idea, at least for a test session.

If you beat me to it, would be interested to see how you do it.  Likewise if I do something, I'll be sure to share.

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9 hours ago, Philbo said:

I need to procure myself a backup.  On a side note, I've heard the 91 model year used a standard vacuum boosted setup.  Is that true?  If so are parts for those hard to come by and is there any reason why you couldn't replace the Teves mk II with that if it died?

I have so many back ups is because I have presently four drivers. I also sell parts now and then of what I have too many of. I would sell pump/motors if anyone is interested.

For some reason Wisconsin was a bit of a "hot bed" for Reattas and Rivieras. I think it has to do with how many Buick dealers there are. I also am about 2 miles from probably the largest You Pick yard in the state and they presently have at least 5 Reattas and 6-7 Rivs, plus Troferos and Cadillacs of our vintage so I can get the parts I need as things break. However I do carry an extensive amount of new parts not readily available at local parts stores [bought from Rock Auto] so I have minimal down time.

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On 12/28/2019 at 2:43 PM, 2seater said:

The pump charging time sounds pretty normal and the large accumulator from completely empty to full can approach one minute.

I went back and checked. I was thinking wrong, it was just under 45 seconds for the ABS and brake lights to go out and 62 second to full charge. That was after sitting overnight.

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10 minutes ago, Philbo said:

I went back and checked. I was thinking wrong, it was just under 45 seconds for the ABS and brake lights to go out and 62 second to full charge. That was after sitting overnight.

That sounds good, especially with a larger accumulator. Not wanting to give false information but this is from memory: the lights should pretty much go out at the same time as they are pretty much opposite sides of the same switch and I think this is in the 1400#-1500# pressure range. In use the pump restarts at 2000psi and cuts off at 2650psi. From the data I have gathered from testing 8-10 switches, they are very consistent pressure wise if they haven't failed due to a leak. The point of this is the pump run time between cut in and stop gives an indication of how much fluid is contained in the working pressure range, longer theoretically being better. Many variables involved here such as pump condition, voltage delivery to the pump and of course capacity of accumulator to give a suggested figure but can be another item to compare over time.  

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5 hours ago, 2seater said:

That sounds good, especially with a larger accumulator. Not wanting to give false information but this is from memory: the lights should pretty much go out at the same time as they are pretty much opposite sides of the same switch and I think this is in the 1400#-1500# pressure range. In use the pump restarts at 2000psi and cuts off at 2650psi. From the data I have gathered from testing 8-10 switches, they are very consistent pressure wise if they haven't failed due to a leak. The point of this is the pump run time between cut in and stop gives an indication of how much fluid is contained in the working pressure range, longer theoretically being better. Many variables involved here such as pump condition, voltage delivery to the pump and of course capacity of accumulator to give a suggested figure but can be another item to compare over time.  

thanks for that info.  I'll have to check all that and log it in my log book.  I plan to do a complete brake fluid flush every year so I can re-check it at the same time at least.  I have not checked to see if the switch is leaking yet.  Is that hard to do? The lights do go off pretty much at the same time.

 

I do have the GM pressure gauge that you hook up in series with the accumulator so I could check the pressures.  I picked it up off of Ebay. I haven't tried measuring anything yet, but might check my system against the numbers you gave.

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Wow, that pressure gauge will let you do almost everything I do with my test rig except measure the actual fluid volume. With a helper in the car to watch the lights you can check the pressure settings of the switch, plus of course check cut in and pump stop fluid pressure. A good deal all around. As for checking the switch, just pull the electrical connector from the end and check for brake fluid. A dry connection and you are good to go.

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  • 1 month later...
Philbo

So was doing some follow up inspection of the brake system now that it has been some time since replacing my accumulator and bleeding the brake system.  I noticed that the brake fluid level had dropped slightly.  On further inspection, I noticed that brake fluid was weeping very slowly from where the accumulator mounts.  I can't really tighten it.  What do you all think? faulty O ring maybe?  I did a search and could not find any forum posts with the same problem.  Also, if I take the accumulator back off to replace the O ring, do I have to re-bleed the brake system?  The leak is extremely slow as near as I can tell.

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2seater

No, you do not need to bleed the system after accumulator replacement. As a matter of fact it must be emptied before it can be safely removed by pumping the brake pedal at least 25 times with the key off. You will feel the brake pedal get hard when boost is depleted and give it a few extra for good measure with the larger accumulator. Could be a cut o-ring, or is it possible there was one was stuck in place and there are now two in place? It should seal right up with just hand installation, extra torque does no good. Is it possible it is seeping from somewhere else? Is the reservoir overfilled? The level must be checked with the accumulator empty  and the normal running level will be 1/2" or more below the full mark.

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Philbo
24 minutes ago, 2seater said:

No, you do not need to bleed the system after accumulator replacement. As a matter of fact it must be emptied before it can be safely removed by pumping the brake pedal at least 25 times with the key off. You will feel the brake pedal get hard when boost is depleted and give it a few extra for good measure with the larger accumulator. Could be a cut o-ring, or is it possible there was one was stuck in place and there are now two in place? It should seal right up with just hand installation, extra torque does no good. Is it possible it is seeping from somewhere else? Is the reservoir overfilled? The level must be checked with the accumulator empty  and the normal running level will be 1/2" or more below the full mark.

Yeah definitely not two O rings because the old one is on the old accumulator. I did also wet the O ring with brake fluid before installing it like the factory repair manual says to do.   

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Ronnie
47 minutes ago, 2seater said:

The level must be checked with the accumulator empty  and the normal running level will be 1/2" or more below the full mark.

2seater is right.  It's important to fill the reservoir this way.  The reservoir will overflow if you add more fluid after the pump has filled the accumulator and pulled the fluid level down below the full mark.

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Philbo
7 hours ago, Ronnie said:

2seater is right.  It's important to fill the reservoir this way.  The reservoir will overflow if you add more fluid after the pump has filled the accumulator and pulled the fluid level down below the full mark.

yes I did fill the reservoir that way.  The level was right at the mark. The other day I pumped the brake pedal until the accumulator was empty to check the level, it was slightly below the mark. 

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  • 2 weeks later...
Philbo

I replaced the O ring on my accumulator today.  So far no leaking but will have to keep an eye on it over the next few days. I did confirm the repair manual says nothing about needing to bleed the system after servicing the accumulator. 

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Studebaker

GettyUp!  Hi Ho Reatta, Away!  Hope she is leak free now and running at those high psi's.

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