Exorcising a '78

[IICrew]

Looking further it looks like the shocks are for 73 mustangs built after 11/73. Which does not exist. So they are for a II. II's were introduced in September of 73 so by november there was no 73's being made. Rock is usually pretty good about their parts listings. This is the first time in 15 years I have been perplexed by a listing of theirs.

So my only remaining question is why not list the TRW. Why does their website say only 2 left. Yet still says 2 left after I bought the 2.

 

[2Blue2]

the ole’ bait and switch...

 

[IICrew]

&*^^ %%$#& *^*(&^% ^& Brake Booster. *%$#@(*(**&^%$# *&^&^%%$#%^* Booster.

I replaced the front brake lines. Created some other issues since the 90 degree adapter and new hose do not match. So brake line is temporarily zip tied to the chassis. Seemed to work great in the barn. Drive it 20 miles and it starts acting up again. Car will not roll. Front wheels hot as hell. I was so mad and frustrated.

I brought it back home and started going over it. In the past I usually park it and look at it the next day or two. Yesterday I was determined to take it on a longer drive so I kept at it. Front wheels will not roll. Loosened bleeder screw and fluid shot out under pressure. Pumped up the pedal and it didnt feel right. Felt notchy. Loosened master cylinder and wheels would roll again. Came inside to eat lunch then returned to the car. Pumping the brakes the wheels would roll with master cylinder tightened back down. Pedal felt normal again. Took it on a couple mile drive and it acted fine. Drove a few more miles and it started again. Being the first 80 degree day around here this season I started thinking heat was contributing to the issue. I let car sit and run in the barn with heat cranked up. After about 15 minutes it started doing it. As I repeatedly pressed the pedal it got to the point I could pop the pedal back up.

The brake booster has something wrong in the plunger mechanism. When cold it acts normally. Once you press the pedal repeatedly or let it get warm it starts hanging up. The more you press it or the warmer it gets the more it hangs. I have never dealt with a brake booster doing this. Worked on cars or as a service advisor for decades. It feels okay when cold. Pedal returns to normal. Repeated presses it does not return. It starts popping then raises when you lift the pedal. More you press the pedal louder the popping is and lower the pedal stays. Bench testing with a heat gun on the snout its really bad. Explains why when I would test it it seemed to be okay. Took some heat building up to act up.

I am so mad at myself. All this time I have fought an intermittent issue that I could not properly describe to my self.

Stole the master cylinder and booster as an assembly from the Mach I. Hate cannibalizing that car but it was a known good unit. Even if the booster is rusty and probably original.

Drove it for about 45 minutes. Pedal stays nice and high. The car rolls as it should. Wheels were nice and cool to the touch. Takes more force to stop the car but I can deal with that. I am now able to lock up all 4 wheels in a panic stop. I had the rod so short it would not lock up before. Neighbors had family over as I am flying down my driveway and skidding to a stop several times. Hopping out and checking the skid marks. From the stares I was getting I was certainly a source of entertainment. Good thing the actual owner likes me as her family always steers clear of me. I mow her yard when they don't show up and keep her driveway clear in the winter but they always look at me as the weird old man to stay away from.

Next up will be rotors and pads. The rotors have blueing and pads have to be scorched. Then get the axle and trans mount back to stock configuration and see if that helps the minor vibration still there. Now I can feel the vibration change with accel or decel so I think the remaining vibration is driveline angle. Which I probably caused trying to figure out the brake vibration.

 

[LILCBRA]

Good to hear you've got it nailed down!

 

[manicmechanic007]

I have seen half a car be replaced due to some old fart adjusting the master cylinder push rod length too long
This caused the brakes to be applied with his foot off of them
Made the car (New Taurus) shimmy real bad
The brakes were being applied on a diagonal I believe
Kept noticing only the left front wheel was getting hot
This was only happening about an hour into a test drive
The guy had been complaining of low brake pedal and mushy brakes
Someone must have showed him the brake booster push rod adjustment and spec
Maybe back yours off a bit IICrew for a test

 

[IICrew]

007 I had adjusted the rod so short the brakes would not lock up at all. Pedal was almost to the floor. The shorter rod would allow a longer drive before acting up. By longer I mean 20 minutes on surface streets. When it was the correct length I could not go around the block without the front wheels locking up on gravel. The actual problem in this case is the plunger/ springs mechanism in the booster itself.

Symptoms you describe is what I was experiencing. Short drive everything fine. Longer it was driven the more it vibrated. I had not taken it on a long drive until a couple weeks ago because of the vibrations. That long drive is when it all came together for me. Before the vibrations felt like the entire car. On the long highway drive it was yanking the steering wheel left and right.

I had replaced the flywheel, transmission, wheels and tires, added and removed shims to axel and trans. Replaced master cylinder and brake lines. Again. Trying to get this under control. I do 99% my own work but I paid several shops to help me find it. All they did was recommend throwing parts at it in the end. No one thought brake booster. Purchased two angle finders myself when they said driveline angle is fine. Bought a lazer level to shoot lines down the chassis to make sure the engine was not crooked in the engine bay.

It all came down to the N.E.W booster Never Ever Working right. Somehow the mechanism to return the pedal hangs up. Not all at once. It slowly makes the pedal lower and lower. When cold I could not lift the pedal. When hot it pops back up when lifting it.

 

[manicmechanic007]

So, all is well now then?
Your 2nd new booster should have come with the rod adjusted to thecorrect length
I did not realize your pedal was hanging up
The springs in the master cylinder are real strong as well
Not a lot of options on another booster right? You had to use the same brand?
At least you have a ton of new or working stuff for your car

 

[IICrew]

It's better. Not vibration free yet but I think the rotors are warped now from driving with the brakes partially applied. I still need to remove the shims from the trans mount as well. I took out the rear axle shims which helped some.

I stole a booster and master as an assembly from the Mach I I have. Booster is original and master was new when I got the Mach running a couple years ago. Shame to do that but it was a known working unit. Should have done it 2 years ago. I will send out a core booster sometime this summer and have it rebuilt by Cardone. They are the only place I am aware of who rebuilds them. I tried to get the booster apart and replace the spring assembly but only hurt my back trying to twist the two halfs apart.

I now need new pads and rotors. The rotors are blue and the pads have to be scorched. Then I can hopefully get it running at 75 mph without fear of it grenading on me. I want to do the Power Tour in the next year or two. We like to take day trips and I want this to be reliable/smooth enough to do that. Once this gets sorted A/C is the next project. I have a new condensor and rebuilt heater box from an A/C car ready to go in. Just need the compressor, brackets and lines made when I get to that point. Ohh and the motivation to pull the dash apart. uggghh.