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Philbo

Brake Flush Questions

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Hi, sorry if repeat topic, but could need some clarification. I plan to flush and bleed the brakes on my reatta. I have read both the intruction here and the factory repair manual.  Both say that you can bleed the fronts like normal brakes.  Do you have to turn the key to charge the accumulator first or will it work without doing that.  My other question is about flushing.  Is it better to perform the flush through the fronts or the rears?  I plan to just cycle the fluid through until all the old stuff is out. Is it better to do that through a front brake and then flush the rest once you get the reservoir and pump flushed out or do it through a rear brake?  Thanks for the advice.

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The pedal may feel differently with the accumulator empty vs with pressure in the accumulator but it should work either way. on the fronts  I would do it with the key on. Start with the wheel that is the farthest from the master cylinder and continue with the next wheel farthest away until you have them all done.  Be sure you don't ever let the reservoir run empty. If you do air will get in the pump and it might cause you lots of headaches.

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I have one more question.  So the instruction says that you put light pressure on the pedal and let the motor pump the brake fluid for you.  Is there any reason you cannot/shouldn't do the fronts the same way?

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I know this may sound odd, and it is a different type of system. The rear brakes use fluid from pressure pump directly, modulated through the brake pedal, hence there is a direct path from the reservoir through the pump and out to the rear brakes. The front brakes are more conventional with the pump supplying boost pressure to the master cylinder which amplifies brake force from the pedal. Due to the design of the system, if the boost pump fails and the accumulator is depleted, there is no rear braking, only the front brakes in non-power mode.

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2 hours ago, 2seater said:

I know this may sound odd, and it is a different type of system. The rear brakes use fluid from pressure pump directly, modulated through the brake pedal, hence there is a direct path from the reservoir through the pump and out to the rear brakes. The front brakes are more conventional with the pump supplying boost pressure to the master cylinder which amplifies brake force from the pedal. Due to the design of the system, if the boost pump fails and the accumulator is depleted, there is no rear braking, only the front brakes in non-power mode.

thanks for the explanation. That makes sense, however I do wonder why they did it that way.  It is an interesting brake system for sure.  The brakes do feel great on it though.

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The Teves brake system is the best. If you have newer pads and rotors with a good accumulator stopping is among the best I have ever experienced.

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22 minutes ago, DAVES89 said:

The Teves brake system is the best. If you have newer pads and rotors with a good accumulator stopping is among the best I have ever experienced.

I agree. It has saved me from hitting a deer twice.  Both times all I had time to do was jump on the brake pedal. The car has always stopped straight as an arrow without sliding a tire.  On one occasion it stopped so fast my daughter was startled and couldn't believe we hadn't hit the deer as close as it was to us when it jumped out into the road..

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What has not been mentioned is that first you must remove the reservoir of fluid. This is best accomplished first by having the key in the "off" position then by removing the rubber hose off of the bottom of the reservoir tank and draining into a drain pan under the car.  Then reconnect the hose to the reservoir tank.  Now fill the tank with fresh new brake fluid.  Next turn the ignition switch to "on".  Then I release the pet cock valve on the rear passenger side and let the brake pressure push the old brake fluid out until you have new fluid coming out then close the pet cock valve.  Next release the pet cock on the rear drivers side and release the old brake fluid out until you have new fluid coming out then close the pet cock valve. 

Check the reservoir after each tire drain.  Do Not refill the reservoir tank past the fill level.  When the brake accumulator pump is stopped running the accumulator pressurized fluid is rerouted back to the brake fluid reservoir tank and  the excess fluid causes the tank level to rise and fluid should only rise to the full level mark and not above.

Now you turn the ignition key to "off".  Now the front brakes can be drained.  They will be drained by the conventional manner of having a person depressing the brake pedal and holding it down then releasing the pet cock valve allowing the old brake fluid to drain into the drain pan. Then tighten down the pet cock valve to the closed position then release the brake pedal.  Reapply the brake pedal and hold down the pedal until the the the pet cock valve is slowly opened and then allow the old brake fluid to drain into the drain pan.  Continue until the drained fluid is clear (clean).

My '89 has been my garage queen for almost 2 years.  I must change out the brake fluid before I place her back on the road due to the fluid accepting moisture over time.

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I'm nervous about trying to disconnect the reservoir.  I worry I am going to damage the hose or the fitting in the process. Also worried about getting air in the pump.  Could you not just push all the fluid out in the bleeding process?  This is what I was thinking of doing:   

 

1. push all the old fluid out one of the front brakes using conventional method. This to get most of the old fluid out without running it through the pump.

2. once the old fluid has been cycled out for mostly new fluid, bleed the rears.

3. then bleed the fronts again.

 

One more thing.  is there anything you must do to get any old fluid out of the ABS valve unit?  Is that even necessary?

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The abs valve allows the brake pressure from the pump to be maintained while directing the fluid to both rear tires.  Do not worry about the fluid that is in the abs valve as it will be changed through the change out of fluid.  The abs valve is physically located in front of the rear drivers side tire.

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39 minutes ago, Philbo said:

I'm nervous about trying to disconnect the reservoir.  I worry I am going to damage the hose or the fitting in the process.

I share your concerns.  When I flush the brakes I use my vacuum pump that has a cup on it that will suck the fluid out of the reservoir.  I found it really hard to put a hose into the reservoir so I attach a small plastic tube like comes with WD40 to the end of the vacuum pump hose. That allows me to get most of the fluid out of the reservoir and refill with fresh fluid before I start flushing the brakes.  I may have a photo of my setup for doing that. If I can find it I will  post it.

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Here are a few photos that show how I do it.  That doesn't mean it's the best way but it works for me.

brake_flush-1.jpg

brake_flush-2.jpg

brake_flush-5.jpg

brake_flush-6.jpg

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Good practice to vacuum out as much fluid as possible first. My luck with disconnecting the reservoir hose has not been the best either and generally just cut it to remove the pump when required, but eventually it will get too short. I share the concern about running all the dirty fluid through the pump but bear in mind if it is dirty it has been doing that every time the brakes are used and this would be the last time as the brakes are bled. Always good practice to start at the farthest corner, no matter the style of system.

 

I agree completely that the brakes on the Teves equipped Reatta's are excellent. It is difficult to actually do a panic stop, on purpose. I know my first reaction is to ease up and not hammer the brake like you really would when no thinking is involved, but it is revealing. Make sure everything is tied down inside the car and you may swear the front bumper hits the ground under max. braking from maybe 40-50 mph. In a safe place of course.

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Well I finished the brake flush today, also replaced the accumulator.  Went pretty smoothly.   Thanks for the advice.  The brakes feel really good now.  Next thing to fix is my IPC 😛

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To all people posting on this thread.......real excellent information.  I will also be doing the flush and bleed very soon, and this thread answers all the questions.

 

Ronnie......where did you get that black "adapter" that fits between the 1/4" tubing coming from your hand pump, and the small red WD40 tube?  If I cant find the same thing, I might just tape the red WD40 tube to the 1/4" tube.

 

Also, did you put that "rod" between the brake pedal and the seat (and with it applying pressure on brake) during the rear brake bleed?  I guess this is to keep the pump running as you are bleeding the rear brakes?  Not necessary for the front brakes, right?

 

 

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1 hour ago, Studebaker said:

Ronnie......where did you get that black "adapter" that fits between the 1/4" tubing coming from your hand pump, and the small red WD40 tube?  If I cant find the same thing, I might just tape the red WD40 tube to the 1/4" tube.

 

Also, did you put that "rod" between the brake pedal and the seat (and with it applying pressure on brake) during the rear brake bleed?  I guess this is to keep the pump running as you are bleeding the rear brakes?  Not necessary for the front brakes, right?

As you can see I have quite an assortment of adapters and short hoses for my vacuum pump. I believe that tapered adapter came with my vacuum pump.  it's made out of pliable rubber that allowed me to force the red wd40 tube inside it.  A small tube forced over the outside of it works equally well. That is what I used the last time I flushed my brakes. You can see it in the bottom photo below.

 

The rod is an 18" breaker bar that just happened to be handy.   I run the seat up against the end of it to keep the pump running when I open the rear bleeders to flush the rear brakes.  Anything of a similar length would work.  I still get my wife to pump the pedal when I bleed the front brakes.

 

SAM_4162.JPG

SAM_4159.JPG

SAM_4160.JPG

 

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Ronnie......Thats right, I think my vacuum pump came with a small bag of attachments.....I will see if there is one like that.  I was looking at the brake reservoir today and am amazed at how long that one rear section is.....now I see why you had that long skinny adapter and hose. 

 

OK.....18" breaker bar with seat pushed up against it to hold the brake pedal down....will keep that in mind when I do the flush/bleed on my 89.

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Even with the straw setup I feel like I couldn't get all of it out of the reservoir, so I just had to pump it all out.  It took me a lot of fluid, about 2 of the large break fluid bottles. 

 

I do have one more question myself. Does anyone know what the capacity of the Hydac accumulators is supposed to be? I know they are larger and it does seem to take a bit more fluid to fill it up, maybe almost 3/4" drop in the reservoir level.  I'll have to get a more accurate measure tomorrow. 

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1 hour ago, Philbo said:

Even with the straw setup I feel like I couldn't get all of it out of the reservoir, so I just had to pump it all out.  It took me a lot of fluid, about 2 of the large break fluid bottles. 

 

I do have one more question myself. Does anyone know what the capacity of the Hydac accumulators is supposed to be? I know they are larger and it does seem to take a bit more fluid to fill it up, maybe almost 3/4" drop in the reservoir level.  I'll have to get a more accurate measure tomorrow. 

If memory serves, the standard accumulator is .25liter and the Hydac or Wabco is .33liter or approx. 30% larger. I believe my fluid drop (Hydac) is about 5/8". The key is to know where it is when fresh so you have a frame of reference as it ages. 

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38 minutes ago, 2seater said:

If memory serves, the standard accumulator is .25liter and the Hydac or Wabco is .33liter or approx. 30% larger. I believe my fluid drop (Hydac) is about 5/8". The key is to know where it is when fresh so you have a frame of reference as it ages. 

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.

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