99% sure it's the booster. Thoughts?

[Cubey]

So the brake system acts as such:

- Pedal is rock hard if parked for more a couple hours. (Loss of reserved vacuum)
- Pedal sinks far down to the floor when it gets vacuum into the booster when pressing the pedal. Feels spongy, a bit slow coming back up.

Because the pedal is so hard without vacuum, I don't think it's the hydraulic system. You'd think there'd be some sponginess without vacuum, if it's a hydraulic problem?

$80 for a booster after 20% off from oreilly or autozone, so I guess I need to just try that first. That's the easiest thing to change too. I had to replace the booster in the RV, so I know they can go bad.

 

[Kdo58]

I replace booster and master cylinder at the same, usually the master cylinder leaks into the booster and ruins it.

 

[franklin2]

Sinking all the way to the floor with the engine running does sound like the booster is faulty. High firm pedal without the engine running is a sign the brake system hydraulics is ok.

 

[Cubey]

I replace booster and master cylinder at the same, usually the master cylinder leaks into the booster and ruins it.

Way ahead of you. I ordered a Raybestos one from Walmart for the same price as other online places. Better return window (90 days) and easier. Almost half the cost of Oreilly/Autozone.

I hate messing with brake bleeding. I might pay $18 for some speed bleeders for the rear. Cheap for not pulling my hair out trying to bleed it. Yeah gravity is a thing, if you don't forget and let it all run out.

 

[Cant Write]

Do you have the whoosh sound as well when pressing the brakes? Isn’t that another sign of a bad booster..

 

[Cubey]

Do you have the whoosh sound as well when pressing the brakes? Isn’t that another sign of a bad booster..

Not sure. Kinda? Maybe? The RV sorta made a sound too with it's booster and it was definitely working right.

I'll try to remember to record a video, the next time I start it up.

 

[franklin2]

Way ahead of you. I ordered a Raybestos one from Walmart for the same price as other online places. Better return window (90 days) and easier. Almost half the cost of Oreilly/Autozone.

I hate messing with brake bleeding. I might pay $18 for some speed bleeders for the rear. Cheap for not pulling my hair out trying to bleed it. Yeah gravity is a thing, if you don't forget and let it all run out.

1. Take the lines off the old master cylinder and cap them off.

2. Bench bleed the new master cylinder.

3. Swap the assembly out, hook the lines back up but leave them SLIGHTLY loose.

4. You will need a helper to press the pedal to the floor. Fluid should squirt out of the loose fittings. MAKE SURE THEY HOLD IT TO THE FLOOR AND KEEP IT THERE. Tighten the lines up. You are ready to go, they can lift the pedal. If you want to bleed it again you can, just get your helper to hold it to the floor again and then crack the lines one at a time. Once they are tight they can lift their foot off the pedal.

 

[IDIBRONCO]

Do you have the whoosh sound as well when pressing the brakes? Isn’t that another sign of a bad booster..

It seems like Fords of this era all had boosters that made that sound. That's what I've seen. Just like the power steering pumps whine and the electric fuel pumps on has engines with EFI are loud.

 

[Cubey]

1. Take the lines off the old master cylinder and cap them off. I've never understood benchI

2. Bench bleed the new master cylinder.

3. Swap the assembly out, hook the lines back up but leave them SLIGHTLY loose.

4. You will need a helper to press the pedal to the floor. Fluid should squirt out of the loose fittings. MAKE SURE THEY HOLD IT TO THE FLOOR AND KEEP IT THERE. Tighten the lines up. You are ready to go, they can lift the pedal. If you want to bleed it again you can, just get your helper to hold it to the floor again and then crack the lines one at a time. Once they are tight they can lift their foot off the pedal.

I've never understood "bench" bleeding. "Do a task, but the hardest way possible!". Just mount it on the booster and "bench" bleed it there with the pedal. I do still have an old bench bleed tool kit, with the little plastic fittings.

I didn't even "bench" bleed the one on the 64 Bug at all because lots of people say there's no point. And it works fine.

Perhaps I could get someone to help out here.

I've had good luck with Gator/Powerade bottle with the cap drilled twice (1 for hose, 1 for breather) for a 1 person brake bleeder. Getting a hose to stay on has always been the issue.

 

[Brian VT]

I've had good luck with Gator/Powerade bottle with the cap drilled twice (1 for hose, 1 for breather) for a 1 person brake bleeder.

MightyVac.

 

[Old Goat]

My experience, when you hear a whoosch under the Dash when pushing on the Brake Peddle, Time to replace the Booster.
Another symptom, if you have one good application and push the peddle a 2nd time and not much or nothing there, Could be the Booster., or the Vacuum Pump.
That was my last experience.

Checked the Vac pump and it was doing it`s job, Checked the check Valve on the Booster and it was ok.
Connected the HF Vacuum Gauge in the Vac hose to the Booster, placed it under the Windshield Wiper to see what was going on.
It was when applying the peddle, the Booster just about dumped all the Vacuum on the first push.

Replaced to Booster, and that is when I up graded the old rusty MC as used up to the 86, to the aluminum/clear reservior one as used 87+.
Never had such good brakes.

Bench bleed the Master Cylinder before installing it and chances you may not need to bleed the Hydraulic system.
But they probably need it anyway, the system should be flushed every 2 years, Fluid should be clear as comes out of the bottle, not the Prune Juice stuff that gets flushed out....

I replaced the leaky R/R Wheel Cylinder couple weeks ago, and then gravity blead the rears. Have a gator Bottle with hole drilled at the top with a piece of Coat hanger bent into an "S", then hang it on something and push on a clear vinal hose on the Nipple. and let it dripple into the bottle till it runs clear.
Did both sides, just keep an eye on the MC so it does not run dry. east/Simple.

I also agree, change both MC and Booster at the same time.
If you are loosing fluid in the MC, and you see no leaks. It is going into the Booster.
Don`t skimp on things when it comes to the Brakes.

Bench bleeding is simple, place Booster in a Vice, purchase the Bleeder kit at your favorite auto supply.
Screw the fittings in the threaded ports, attach the 2 hoses, and place them into the Reservoir. Fill with Fluid. With a Screw Driver push in the MC where the Booster Rod would go. Push in several times till you see no more bubbles.
Then attach to the vehicle.

be sure to adjust the Booster Rod to the MC for the proper clearance.

Here is a video on the adjustment.
Mount Booster on the vehicle then do the adjustment.

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Goat

 

[Black dawg]

is check valve holding?

 

[WrenchWhore]

Sounds like a booster to me. I had to do a booster/master right after buying my current truck. I'd highly recommend you bench bleed before install. It usually takes about 100 or so full strokes of the master cylinder before the air finally clears out visually. At least that's been my experience.

 

[rreegg]

I’ve had the whoosh and a hard brake pedal (after letting the truck sit with engine OFF) both before and after replacing a b booster. Not saying there aren’t other issues with the booster but those aren’t smoking guns in my opinion - and I could be wrong too

 

[Cubey]

MightyVac.

I bought one once. It was like eggshell. It broke to pieces in no time. Never again.