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Ford Bronco Parts - Classic Vintage Early Bronco Parts

Mustang Cobra Hydroboost

Tech article by admin and filed under - Hydroboost, Brakes

Tech article by Jesse Bauman bronko69er

After multiple inquiries on how I did this, I figured it was time to use all the pics I took and write a tech article. I’ll preface the article with a short statement about the exact application, and what I started with.

I installed this set up on a 1969 Bronco with a carbureted 302, stock Ford power steering, 1.5″ body lift, stock hood, 4 wheel drum brakes, replacing a stock manual master cylinder. If you have a different setup, your installation steps may deviate from mine.

I began by obtaining a master cylinder, hydro booster, and all lines and hoses form a 1998 Mustang Cobra SVT. This year came with a MC with a bore of just a hair over 1″, (close to a stock manual booster’s bore). It is my understanding that 1996-2004 Cobras came with hydroboost though I’m not sure the difference between the years. The price for these boosters & MCs are in the $100-$150 range, I scored mine for $75.

I began by removing all the hoses, lines and the MC and labeled the ports on the booster with letter stamps. Not pictured is the 3rd port which I labeled “RET” for the low pressure return to the pump. The low pressure return is the “banjo like” fitting and is the smallest of the 3 threaded ports. (pics 3113,15)

In order for the new MC to clear the hood, the booster’s mount plate needed to be rotated 90 degrees. Remove the pressed in mount plate studs via method of your choice, easy with the BFH! The new plate orientation will angle the assembly ~15 deg. away from the motor instead of ~15 deg. upward. To achieve this I put the booster in a vice and used a hammer on the mount plate to move it counter clockwise (CCW) which loosened the retainer nut. Once the nut was loose I rotated the mount plate to ~180 deg. from its original location, tightened the nut by hand, and hammered the plate back to 90 deg. to re-tighten the nut. This might take a few iterations to get the nut properly tight and the bracket positioned correctly. See above pic (3115) for new plate orientation.

Next I removed my stock manual MC form the firewall by removing the brake lines, pedal linkage, and 2 bolts to the firewall. (pics 3118-19)

In order for the booster to fit the stock firewall pushrod hole, a small trim was required on the mount plate to clear the rib on the firewall. (pic 3120)

I was then able to hold the booster up to the firewall, mark (transfer punch or sharpie) and drill the mount holes.
I found out after drilling the other 3 holes, that the lower right in pic3123 was really close to one of the existing steering column bolts holes. It’s probably best to align that one first and then mark and drill the other 3. (pics 3121,23,25,64)

After drilling the holes I could temporarily mount the booster to size the push rod correctly. The stock booster rod is too short so I lengthened it using the eye part of my manual booster’s rod and a coupler nut. I cut off the eye of the booster’s rod and threaded as much as I could of what was remaining using a 3/8-24 die. I ground some flats on the rod to hold it with vice grips. (pics 3127,28,32,33)

I did the same thing on the eye section of the stock MC rod. I also had to bend the rod slightly to accommodate the ~15deg angle of the mount plate. This allows the rod to enter the booster without binding. Adjust the pedal before installing the brake light switch and pin. Once you have the pedal adjusted to where you want it, then re-install the switch (pic 3156,57,63)

With the linkage all set you can fully bolt the booster to the firewall. Now, onto the plumbing! I’ll start with the brake lines. I chose to use hard lines from the MC to the H-block so I needed 2 adapter fitting.
1 – M12x1.5 male bubble flare by 3/16 female brake line (front line size)
1 – M12x1.5 male bubble flare by ΒΌ female brake line (rear line size)
The fittings cost about $9 each. I got them form Williams Oil Filter Service in Tacoma, WA (866) 627-8163. They will ship. I bent 2 pieces of hard line (I think I used 24″ but measure for your body lift) to look like this. (pic 3126, 41)

For the PS fluid lines I went to my local hydraulic hose & fitting house and had some lines made up. I just brought in everything I had so there’d be no guessing. The low pressure return line is easy, just 3/8″ ID soft line like your stock PS box return. For the booster side of the LP return line I just cut the end off the existing hard tube, slipped the hose over it, hose clamped and it was done. For the pump side of the return, it’s best to have a dual return pump. I did not at the time but was able to use a “T” to combine the return from the gear box and the booster. It’s best to get the “T” as close to the pump as possible and to have the pump leg and the box return leg on the parallel sides of the “T”. The booster return should be on the perpendicular side.. If the booster is not allowed to “vent” via its return line, slow pedal return can result. I had it plumbed wrong in the pic (which I learned later) just for reference (pic 3161)

For the pump to booster line I used a fitting for my pump (don’t know the size but the hose supply place had it in stock) and a compression fitting to connect to the hard line on the booster side.
For the booster to gear box line I used a fitting for the booster (stocked by the hose supply place) and a compression fitting to adapt to the hard line end of an old PS hose. The hoses ended up being around 20″ & 26″ but it’s best to measure for yourself.
All the hoses fitting and related plumbing parts cost me about $75 at my local hydraulic hose and fitting house. (pic, 3110,11,16,17)

Now hook up all the lines, fill up the fluids and start bleeding. Bleed the brakes first and be sure you have a “normal” feeling pedal. (Depending on MC bore & stroke to caliper & wheel cylinder volume ratio, the pedal will have varying degrees of “firmness”. Without the engine running, hydroboost brakes will feel exactly the same as manual bakes (different from a vacuum booster).
Once you are confident that the brakes are bled properly, proceed to bleed the PS system. Bleeding a PS system with hydroboost is the same as without so in an effort to keep this article short, I’ll let you research that on you own. Enjoy, and take it easy for a while or I promise, you’ll be kissing the windshield. (pics 3158,59,60)

Tech article by Jesse Bauman bronko69er

3 Responses to “Mustang Cobra Hydroboost”

  1. Spot Says:

    Nice write up, you must be working in an engineering environment 

  2. Bronco Corral Says:

    footnote, USE LOCTITE OR JAMB NUTS ON THE MODIFIED PUSHROD THREADS! the threads CAN and DID come lose on me and had brake failure resulting in accident.

  3. BRONCO635 Says:

    I read your article and very interested in installing in my 71 bronc.have 1 question does it have to come off of a cobra mustang because I ,well my wife owns a 04 gt mustang with hydro boost.so when I go to the yards hunting didn’t know if I had to single out a cobra or just a gt. Then I would have our car here as reference.thanks ahead of time.

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