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Sticking Calipers - Brake Pump?


BEMSTER 3
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I've had my Reatta for several months now, and although it was incredibly poorly maintained it and doesn't make financial sense to keep fixing it, I've grown attached to it. That said, I've hit an issue that may scrap my car. Both front brake calipers are failing to retract all the way from the rotor and as I understand it, they have been for longer than I've owned the car. Obviously it has negatively impacted the braking of my car and I can't take it on the highway. I've taken it to several shops and the brake hoses and calipers on the front have already been replaced, but the best anyone can tell me is that there is some sort of problem with the brake pump.

 

Basically, what I need to know: Is the brake pump easy enough to replace for an inexperienced owner? Is it worth buying a $400+ pump when the car itself is only worth around $1500? Thanks to anyone that can help, I would really like to keep this car on the road as so many of them have disappeared already. 

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Is the brake fluid clean?   When some shop replaced the hoses and calipers there is only about 10% chance they flushed the system.....getting fresh fluid in the system may clean up any problems and you will be good to go.

Historically the Teves master cylinder is trouble free........the master cylinder would be the place that would not let the fluid flow back from the wheel cylinders......

There are basically two parts to the Teves brakes (plus the ABS) (1) the master cylinder and (2) the boost system (this is the "power" part of power brakes)

The boost pump builds pressure so you do not need to use lots of foot pressure to stop the car......it has nothing to do with fluid returning from the calipers.

I have attached  a working drawing from the Teves training manual.........after looking at that,  you could have a ABS valve that is sticking or dirty.

However notice that the right and left front go thru different valves.........so why are BOTH calipers not returning fluid?

schematic  II.jpg

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The statement that there is something wrong with the brake pump is pretty vague. Does the pump run? If the pump runs, how much does the fluid drop in the reservoir when the accumulator charges? In other words, have you tried the tutorial on doing the brake test?

 

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On 9/3/2018 at 3:52 PM, Barney Eaton said:

Is the brake fluid clean?   When some shop replaced the hoses and calipers there is only about 10% chance they flushed the system.....getting fresh fluid in the system may clean up any problems and you will be good to go.

 

I actually flushed the system myself before bringing it to the shops, so the brake fluid is still fresh.

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On 9/3/2018 at 6:49 PM, 2seater said:

The statement that there is something wrong with the brake pump is pretty vague. Does the pump run? If the pump runs, how much does the fluid drop in the reservoir when the accumulator charges? In other words, have you tried the tutorial on doing the brake test?

 

The pump does run, and it seems to be holding pressure well. I haven't done the fluid drop test yet, but I will go and do that right now. The accumulator was recently replaced so I have done a few of these tests already.

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On 9/3/2018 at 2:33 PM, BEMSTER 3 said:

... Both front brake calipers are failing to retract all the way from the rotor and as I understand it, they have been for longer than I've owned the car. Obviously it has negatively impacted the braking of my car and I can't take it on the highway. I've taken it to several shops and the brake hoses and calipers on the front have already been replaced, but the best anyone can tell me is that there is some sort of problem with the brake pump.

 

Basically, what I need to know: Is the brake pump easy enough to replace for an inexperienced owner? Is it worth buying a $400+ pump when the car itself is only worth around $1500? Thanks to anyone that can help, I would really like to keep this car on the road as so many of them have disappeared already. 

 

I don't think there is anything that actually "retracts" the brake pads away from the rotor. When you let off the brake pedal pressure should be relived on the pads so the rotors can turn freely. If that isn't happening and there is still pressure on the pads I would agree that you have a problem. Finding the problem will require some hands on troubleshooting to figure out what is going on.

 

You should check to make sure the return spring on the brake pedal is moving the pedal all the way back to the top. If the pedal isn't returning as it should it could cause some pressure to be held in the master cylinder and calipers.

 

Next, jack up the front of the car and remove the wheels. Turn the key on and allow the pump to build pressure. Apply the brakes several times and the let off.

 

Try to turn the rotors by hand. If you can turn them by hand everything is fine even if you can feel the pads slightly dragging on the rotors.  If you can't turn the rotors, open the bleeder valve on the caliper to relieve any pressure that might be in the lines.  Take note if there is any air that comes out. After doing that see if you can turn the rotor by hand. If you can't, remove the pads from the calipers and make sure they are installed correctly and check to make sure the calipers are able to move freely in the mounting brackets. If you detect any air coming of the bleeder you should bleed the brakes again following the instructions on my website. How To Flush & Bleed Brakes

 

Let us know what you find.

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I dont know if Buick used the same system. I had a GMC pickup with ABS and the front left brake caliper would hang. It was the ABS module. The computer wouldnt release the valve all the way and the brake caliper would stick a bit and get hot. We had replaced the caliper twice before we figured it out. There was a ABS eliminetor kit that we used to fix it since there was no  ABS computers available just used ones that might also be broken.

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Look closely at the front brake hoses. It is not uncommon for the inside of the hose to collapse and prevent return fluid flow. I didn't have problems with non-release of the brakes but I was surprised at the poor condition of the hoses, particularly where they twist and flex, when I did some unrelated work under the front end.

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