Master Cylinder Questions

[KYBlueOval]

I'm at the point of connecting the brake lines to the Master Cylinder, but do not know which circuit is for the Front Brakes and which is for the Rear Brakes.
I have a HydroBoost from a 2003 Mustang GT, and a new MC. The MC is not marked in any way as to front or rear. Neither was the one that came on the HydroBoost. A local Ford dealer "guessed" that the rear circuit was for the front.
Any words of wisdom regarding the bleeding of this MC? I assume (dangerous word) that it is done on the car, using the two bleeder screws. Is that correct?
I can post a picture if necessary.
Thanks
John

[RICH MUISE]

I'll look at my setup, but I think the Ford dealer was guessing wrong. Not sure if the proportioning valve my lines are going thru will allow for a proper determination, but I'll look after my coffee.
You said new master cylinder, but is it the Mustang style, or Wilwood/standard style? If it is the Mustang style, they cannot be bench-bled. I mentioned that before, and suggested making a bleeder jar with two hoses so you could bleed both at the same time.

[RICH MUISE]

I ran the front port on the Master to the front inlet port on the proportioning valve. The front outlet on the proportioning valve then goes to the front brakes. I'm sure I checked that all out, like you are doing, before I ran the lines. Seems like another lifetime ago.

[gasman826]

Bigger reservoir to the front brakes and smaller reservoir to the rear.

[KYBlueOval]

A picture is worth a thousand words.........Here is what I have. I don't see anything that "divides" the MC. Having said that, the larger volume/area of the MC is in the rear. So If I had to guess,the rear circuit is for the front brakes. Just a guess.
Rich , you spoke about a proportioning valve. I did not get the factory proportioning valve, if there is one, when I got the HydroBoost, but I do have a Wilwood Proportioning vale in the rear brake line. Is that an issue?
Thanks, Rich and Gary for your help. I do appreciate it.
John

[RICH MUISE]

I'm using a Wilwood proportioning valve as well. Maybe Gary's reservoir has 2 sections, ours is one. You would have to be almost out of fluid for that to come into play with the angled position.
I did get the OEM valve with my hydroboost, but I did not use it because I don't believe it was adjustable, and the Wilwood additionally provided a port for the brake light switch which I wanted/needed if I remember correctly because I needed 2...one for the brake lights and one for the computer.!? My second one is on the brake pedal assy.
I'm assuming when you said "nothing dividing the MC", you actually were talking about the reservoir.
If your assumption about the rear port going to the front brakes is correct, mine have been hooked up wrong for 58k miles and work just fine.

[KYBlueOval]

Yes Rich, I was referring to the reservoir, when I said MC.Duh! I think I will check the inventory at the local Pull-A-Part and see what they have, and how it is plumbed.
John

[RICH MUISE]

John, any follow-ups on this?

[rmk57]

 I was always though the larger reservoir was for the front as the calipers take more fluid as they wear or more so than the rear drum wheel cylinder's.

[thomasso]

You are correct.

[RICH MUISE]

As mentioned, the hydroboost setup we are talking about uses the single reservoir for both m/c cavities. See the pic John posted. I'm still curious what John finds out checking oem setups at the salvage yard.

[KYBlueOval]

The Street Rod Nationals start tomorrow, here in Louisville, and there are several Brake Vendors, Wilwood,ECI and others, that will be here. My plan is to show them the MC and ask the question as to which port should be connected to the front brakes. Stay tuned.........I'll tell you what they had to say.

[KYBlueOval]

I took the MC with me to the Street Rod Nationals and posed the question about which port is for front or rear brakes, to several vendors of brakes and brake parts. Bottom line........They didn't know.
I did run into a friend that works in an auto parts store. He is very knowledgeable, having been at it for 35+ years. He said the Smaller brake line port(smaller fitting) is usually for the front brakes. Although the reservoir is not divided, the larger portion of the reservoir is above the smaller port, which is the port closet to the firewall, on this particular MC. The MC I'll be using, is made such, that if it were to run low on fluid, what fluid was there, would flow to the rear of the reservoir, feeding what I believe is the front brake port. Makes sense to me.
I said I would go to a Pull A Part yard and see if I could make any determination. Did that yesterday, in the 95* heat. I was sweating like Mike Tyson in a spelling bee!
Here is what I found........(There were plenty of Mustangs, but no GT's, my Hydro Boost came from a GT) The two lines coming out of the MC go to a distribution block. So you can't say with certainty, which is the front and which is the rear. The fittings on the two lines coming out of the MC , that go to the distribution block, are identical. So the smaller port theory, doesn't work with this MC.
From the distribution block, there are three output lines. Separate lines to the Left and Right Front Brakes and a third line that goes to the rear brakes.
"I've been told" that, this distribution block has a floating pin inside the block. If, for example, the rear brakes go out with let's say a ruptured hose, the pin will slide to block off brake fluid from going to the rear brakes. Remember, that the MC reservoir has no divider. so if the scenario I just outlined, were to happen and there was no distribution block with the sliding pin, the reservoir would theoretically completely drain, through the ruptured circuit, and there would be no brakes.
If, I'm wrong on how this distribution block works, please correct me.  BTW, to remove any doubt I had about there possibly being a divider inside the MC reservoir, I cut the top off of the old reservoir with a cut off wheel. There is no divider!
Next, is to confirm that the GT Mustangs have the same basic plumbing as what I found at Pull A Part, before I add the distribution block to my Ranchero. Anyone on the Forum have a '98 to '04 Mustang GT, that could send me some photos?
John

[KULTULZ]

I took the MC with me to the Street Rod Nationals and posed the question about which port is for front or rear brakes, to several vendors of brakes and brake parts. Bottom line........They didn't know.

Now that's scary (IMO)

Same as most 'kit' vendors, they don't have the foggiest either. One needs the exact year WSM of the braking system being used to ascertain how the MC operates and what valving is included or needed. You go to GM or other systems in a mix and you are really asking for it.

MC design has changed greatly since the 60's/70's.

As an example, if the MC has bleeders. it most likely has an internal PDV. It may also be designed while the rear piston is for front disc, the secondary piston will be come operational first as to energize the rear drums if DISC/DRUM (elimination of the METERING VALVE). Also, the RESIDUAL PRESSURE VALVES have been eliminated.

Be careful you don't get your hands on one designed for DIAGONAL BRAKING. That will give you an additional thrill.

[RICH MUISE]

Had a guy in a 2007 Mustang Roush at our Saturday night meet. It had the supercharged 4.6, but I was surprised to find it was a sohc, and the booster was vacuum.......so no luck there.
I agree with Kultulz......only way to know for sure is find a same vintage Mustang. My donor was a '02 Cobra 4.6 dohc. Engine won't make a difference, but I'm not sure if the GT sohc had the hydroboost, as I mentioned above with the '07 Roush. They're not that hard to find, if we had our normal 1st. Saturday of the month cruise-in last Saturday, there may have been one or two there. Maybe I'll see if I can contact someone from our local Mustang club.