Brake bleeding questions

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vintageman

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I changed my front drum brakes to a Wilwood front disk brake system and added a power brake booster and master cylinder from Leeds, the calipers are dual piston. After ordering and installing a new proportioning valve from NPT (Item # 2B091-20AA) I bench bled my master cylinder tonight and installed it. My two questions are this, (1), I am not getting any fluid to the rear brakes, I did start out the bleeding without the tool to lock the proportioning valve in place and then installed the original blocks seized up switch to help keep the shuttle valve in place but still do not get fluid to the rear brakes. The master cylinder fluid is not going down at all. for anyone with this proportioning valve, how do you reset the shuttle, there is no "push button". BTW, these are completely new lines and master cylinder and have never had fluid in them until now. Question 2, for the Wilwood dual piston front disk brake caliper, it is currently set up for forward mounted calipers, there are two bleeder screws, one on top of the caliper and one on the bottom, do I loosen both to bleed or just one of them? Also, I have used both standard and metric sockets on the bleeder screw and none seem to fit, any thoughts on this? Thanks for any advice on this.

Tom
 
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Did you try opening the bleed screws and letting the fluid flow under gravity. This may take a while for it to start flowing. You can connect a hose to the bleed screw and then make sure that the open end is higher than the MC. In this way it will gravity bleed but you won't lose any fluid as long as the hose is connected to the bleeder. You only need to loosen the top one since that's where the air will accumulate. Be patient and if the proportioning valve is good fluid should flow.
Based on my experience you are better off removing the proportioning valve and installing an adjustable one. Add a tee fitting for the front brakes. The adjustable valve will help you set the rear bias to meet your setup needs. The drawback is that you won't have a functional brake idiot light which in some way is kind of useless since it doesn't turn on until you press the brakes and senses a pressure differential which may be too late.
I use a 1/4" wrench, but a box-end one.
 

vintageman

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Thanks for the response, I got them bled tonight. I guess it took a lot more time for new lines to fill. Good pressure on all four brakes now. Thanks.

Tom
 

Kilgon

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You might want to get a brake bleeding vacuum pump. Makes bleeding brakes easy and they can also be used to check out other things where you need to draw a vacuum. Some of the other uses are testing the vacuum advance on the distributor, modulator valve on an auto tranny, hvac motors and lines and power valves for your carb. Well worth the cost. Below is an example of one.

 
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vintageman

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Thanks Kilgon, picked one up this morning. Great ideas for the other uses as well and will be putting them to use is the weather allows this weekend.

Tom
 

basstrix

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I like the alternate version. The larger volume container makes is very handy for flushing brake systems. If I didn't already have a hand vac pump, I might think differently...Kilgon makes some good points on alternate uses.

 
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Thie info below may or may not hep. In the latter part of the info (from a file I have on hand) there is reference to the calipers being on the wrong sides, causing bleeding issues. For what it is worth please take a look unless you already solved your problem.


When replacing front and/or rear drum brakes with disc brake components on a First Generation Mustang or Cougar you do not want to go cheap. This is a fairly serious, even if fairly easy, operation. Use high quality parts, preferably in a kit designed to do a full upgrade. I like Wilwood, a reputable brand with a lot of years in this end of the business. Here are the most important things to be aware of:



• Replace the Master Cylinder with one designed for Disc Brake systems. Often the MC bore size is different compared to Drum Brake system MCs. Also, for Drum Brake MCs the fluid outlet port(s) for drum brakes has/have a Residual Pressure Check Valve (RPCV) under the outlet port’s brass seat. The RPCV is needed for drum brakes to keep fluid pressure on the wheel cylinder cup seals so they do not suck air into the cylinders when the fluid cools off. But, for Disc Brake systems such a valve puts needless pressure on the caliper pistons and causes the pad to drag on the rotor under pressure. That results in reduced vehicle performance, overheating of the front pads and rotors, and rapid wearing of the front pads.

https://www.youtube.com/watch?v=WxT9vLO6pOc (00:42)



• Flush the old brake fluid and replace it with fresh DOT3 Disc Brake Fluid. DOT3 is totally compatible with Drum Brake hydraulic components, and differs from DOT2 Drum Brake Fluid in its boiling point is higher – which is needed for Disc Brake systems. Do not mix newer brake fluid types with DOT3 fluid. And never use petroleum fluids (oil of any type) - ever.



• Get a Power Brake Booster, as the Disc Brakes are not a self-actuating design like a Drum Brake system is. I have driven Disc Brake systems without a power booster before. No fun. They work, but power boosted Disc Brake systems are much better.


• Never use copper lines for hydraulic brake systems (Nickel-Copper alloy metal lines made for brake systems are fine). The copper metal alone is too soft and the lines can and will rupture if enough pressure is applied. Use only properly designed steel or Copper-Nickel alloy lines with double flare endings.





• Do not go cheap on brakes, suspension, or tires, ever.



For front disc calipers, be sure to put the calipers on the correct side, otherwise you will never be able to properly bleed the air from the hydraulic system. Refer to the attached graphic, apparently created by Richard Ackerman (I got it from Dennis Keegan), to see how the calipers ought to be oriented. Many thanks to Richard and Dennis for allowing me/us to share this excellent graphic.
 

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vintageman

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Thanks everyone for the responses, I was able to fully bleed the system and everything is good to go now. It just took longer than I thought to gravity bleed the rear brakes. I also picked up the vacuum brake bleeder as was suggested and went through each wheel using it as well. For the front Wilwood disc brakes, the calipers have bleeders on both the top and bottom so that they can go on either side (front and rear mounting). I appreciate the responses and am happy that this part of the project is now complete.

Tom
 

giantpune

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I use the same vacuum pump for oil changes and bleeding the brakes. The one they sell at harbor freight.

After years of bleeding brakes the old fashioned way, i finally tried the vacuum way. I'll never go back.
 

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