Brakes Brakes Don't Feel Right After Sn95 Swap

Its also a good idea to change the power booster to the larger sn95 style... I run a 98 booster with 2004 cobra front and cobra IRS rear a world of difference over the fox brake stuff...no adjustable prop valve....98 prop valve booster and master cylinder with a line lock.

Grn92LX said:

Still using the fox booster. I will bleed them again and hopefully that fixes it. I don't see how an adjustable PV will help the issue i'm having.

Click to expand...

The Fox booster will be OK with a 94-95 Mustang MC.

Bleed. bleed and bleed the brakes again. Make sure you have installed the brake calipers so that the bleeder fitting is at the very top of the caliper. Put the calipers on the wrong sides, and they will fit, but the bleeder fitting won't be at the very top.

The adjustable proportioning valve allows you to adjust the brake balance between front and rear brakes.

Why do you need to adjust the front/rear brake balance? Ever watch a J turn being done in a car chase movie? They go flying along and jerk up the handbrake; the back end of the car swings around to where the front was.
Imagine you are driving down the road and a kid runs out in front of you. You do a stand on the brake pedal panic stop. You have no proportioning valve installed, so the rear wheels lock up first. The car swaps ends and the back of the car hits the kid when it swaps ends. It hits him just like a hockey stick hits a puck, but with a sick, dull thud. Get the picture?


Garden Sprayer Pressure Bake Bleeder

1 each pump type garden sprayer, 1 - 1 ½ gallon capacity (size doesn’t matter much, it just has to be cheap and small enough to be easy to work with)
6-10 feet 3/8” clear plastic tubing
1 each ¼” brass pipe tee
1 each ¼” pipe to 3/8: hose adapter
1 each pressure gauge 0-30 PSI or so – all you’ll ever need is 5- 10 PSI, so the gauge range doesn’t have to be high.
1 each large rubber stopper – this is the hard part to find. It may take some searching to find one that is a snug push fit to the inside of the filler port on the master cylinder. You can use silicone rubber to seal a brass fitting to an old master cylinder cap, but they tend to leak too much.
Home Depot or Lowes has some ¼” brass pipe stock that is continuously threaded in the electric lamp repair department, along with the brass nuts that go with it. This is better than a pipe nipple, since the nuts can be used to secure the pipe in the cap or stopper.
OR if you can’t find the threaded pipe stock,
1 each ¼” nipple, 1 ½”- 2” long

The rubber stopper needs a hole drilled in it for the ¼” pipe nipple or threaded pipe stock. After you drill the hole, use some silicone gasket sealer to seal the pipe nipple as you push it into the rubber stopper. If you used the threaded pipe stock, use the nuts to secure the stock into the stopper.

If you can’t find a suitable rubber stopper, an old master cylinder cap can be used. Drill a ½” hole in the center for the pipe fitting. Cut the brass pipe stock to about 1”- 1 ½” long, the exact length isn’t too important. Push it through the hole in the master cylinder cap and thread one nut on top of the pipe stock where it sticks though the cap. Put another nut on the other side of the cap to lock the pipe stock in place. Apply some silicone rubber gasket sealer to both sides and when it is dry, screw the ¼” pipe that sticks out of the top of the cap into the tee.

Remove the sprayer hose and wand from the garden sprayer. You may find it easier just to cut the sprayer hose off short and connect it to the 3/8” plastic tubing. The idea is that the 3/8” tubing connects to the pickup tube inside the sprayer in a reliable, leak proof fashion. Another alternative is to remove the spray nozzle from the end of the spray wand and connect the 3/8” tubing to the wand. This leaves the hand valve in place and may be useful to start/stop the flow of brake fluid.

The 3/8” plastic tubing connects to the pipe tee using a push on hose barb type adapter. The pipe tee has one port for the gauge, one for the 3/8” hose and the other to connect to the rubber stopper or master cylinder cap that you modified.

Fill the pump sprayer with a quart of brake fluid. Set the garden sprayer on the ground and screw the pump handle down tight, and pump until brake fluid fills the plastic tubing. Then put the modified stopper or master cylinder cap on the master cylinder and pump slowly to make sure that nothing leaks or pops loose. No leaks, continue pumping until you get 5-10 PSI.

WARNING: Do not let the fluid level in the garden sprayer get low, or let the garden sprayer tip over so that it pumps air into the brake master cylinder. This is the only problem with this inexpensive brake bleeder, but it isn't hard to avoid.

Start with the brake assembly furthest away from the master cylinder. On 5.0 Mustangs, it's the passenger side rear brake. Follow up with the driver side rear brake, passenger side front brake and the driver side front brake. Put a 6”-12” length of clear plastic tubing on the bleeder ports. Then open the bleeder ports on the wheel cylinders one at a time and bleed until the bubbles are gone. I use a 2 liter soda bottle with a coat hanger to catch the fluid . DO NOT REUSE THE OLD BRAKE FLUID. Repeat the process until you have finished all 4 wheels. You will have to pump the sprayer several times to maintain the 5-10 PSI needed to do the job. When finished bleeding, loosen the pump handle to relieve the pressure, remove the stopper/modified master cylinder cap and test the pedal. The pedal should be rock hard, and not need to be pumped up to get a hard pedal.

I wouldn't waste my time bleeding it until you put the proportioning valve in. Because you are just going to have to do it again.
Too much brake going to the rear is a recipe for disaster, I believe the valve max is 70% front 30% rear. Locking the rear brakes is like pulling the E brake.

The summit racing valve is only like $40.
Really not an optional mod, especially after defeating the stock one by pulling it apart.

I agree he needs a brake bleed....notice his pbr dual piston front caliper description. They did dual pistons at the same time the enlarged the power booster....there's nothing like standing on the pedal and gliding through an intersection ( I did that). The bigger booster gives more assist...to actually lock the brakes if need be. Think about it...if you use the whole brake system off another car with basically the same weight how could you go wrong. The area of both wheel cylinders on a stock mustang are smaller than the area of the disc brake calipers...meaning less brake fluid volume is applied to the rear. Meaning the front brakes would be more likely to lock up...but with the pbr calipers the area of the dual pistons also means more fluid volume is needed...so in that equation... With more fluid volume needed both front and rear its a recipe for issues. I've been there done that. 99 and up booster and at least 95 prop valve. I have heard of people gutting the valve...never done that or trusted it. I did use an adjustable prop valve but didn't like the way it looked beside my e brake. Smh. Pluss I got in more trouble with it than I needed. Lol

I just used a 93 cobra master and booster. I have a 92 lx coupe, I had to bfh the strut tower to fit it in. It's noticeable if you look for it but otherwise it's hidden by the same massive booster.

FWIW, we had a hard time getting all the air from my recent conversion too (In fact I'm not 1000% sure I still don't have air).
I may have to try the above pressurized method.

Google it...

Interesting,my Wilwood valve is in for more rear brake,out for less,even states this in your link.
Make sure you have the valve all the way in when bleeding the rears(valve fully open).

Good luck

Pressure bleeding is definitely the way to go.Now that I'm older and have more money than time the Motive pressure bleeder is a good buy at $62 shipped.The front calipers are a pain to bleed even with the pressure bleeder,on the sixth time around I got some air through the front bleeders(this with the front end jacked up and tapping on the caliper with a rubber mallet,and yes the calipers are mounted correctly).I ended up going around 10 times before I was sure ALL the air was extracted.IMO,I think if you were doing the 2 man bleed there is a good possibility your brakes will never be FULLY bled,unless you took the day.

Had to remove my strut tower brace AGAIN in order to use the Motive bleeder.I'm getting tired of removing the damn thing whenever I work under the hood,it's staying off for good at this point.