When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
I noticed in my 1980 that my brake booster vacuum line is T-ed off to this. It is located around the driver side wheel well. What is it and where should it be getting vacuum from?
From: At my Bar drinking and wrenching in Lafayette Colorado
I'm not seeing any vacuum lines or any "T" in your photo, but the component shown in the photo is your cruise control. There should not be anything "T'ed" into the power brake vacuum hose. The cruise control transducer gets its vacuum from the manifold fitting (yellow hose shown below).
Vacuum hoses and hookup of cruise control and transducer:
From: At my Bar drinking and wrenching in Lafayette Colorado
That's quite the hack-job of incorrectly hooked up hoses - holy smokes - what a mess. Yank that crap out of there and hook up your hoses correctly per the diagram I've shown you. Yes, hooking up other vacuum accessories (which may be leaking) to your power brake hose is just a really bad idea.
I had a leak on a caliper so I had them all replaced since they were very old. It worked great for about a week, then they went out again. I took it back to see what the issue was and they told me I needed to replace the master cylinder. I bought a new master cylinder, bench bled it, installed it and bled the brakes. I had a nice hard pedal when I tested it, but the pedal went soft again after a few miles. I figured I didn't bleed them enough so I bled them again and got a little air out. Nice hard pedal again, for a few miles, then soft again. Next I replaced the rubber brake hoses, bled them again and had a nice hard pedal. The next time I drove it, they went soft again after a few miles. Right now, with the engine off, the pedal pumps up if I push it 3 times, but goes down if I keep my foot on it.
Meanwhile, you checked the fluid level in the Masters Rez and noticed what?
The Brake Booster:
MUST have a dedicated vacuum line, solo, no sharing, no "T"s.
And not just any line, one that is tagged at the store, Brake Booster Vacuum Hose.
What's not important is using rubber instead of factory steel line.
What's not important is where you tap-in your line from the carb.
What IS important is using designated rubber hose for boosters. When you are buying at NAPA, note the larger diameter of the hose.
Also note the small inside diameter. Its extra thick wall hose. It will not collapse like cheap thin hose.
When installed correctly, with quality hose, you will not need any hose clamps at the carb, check-valve, the one-way valve or the inline filter.
Meanwhile, you checked the fluid level in the Masters Rez and noticed what?
The Brake Booster:
MUST have a dedicated vacuum line, solo, no sharing, no "T"s.
And not just any line, one that is tagged at the store, Brake Booster Vacuum Hose.
What's not important is using rubber instead of factory steel line.
What's not important is where you tap-in your line from the carb.
What IS important is using designated rubber hose for boosters. When you are buying at NAPA, note the larger diameter of the hose.
Also note the small inside diameter. Its extra thick wall hose. It will not collapse like cheap thin hose.
When installed correctly, with quality hose, you will not need any hose clamps at the carb, check-valve, the one-way valve or the inline filter.
There is no leaking fluid anywhere, the reservoir stays full.
BTW, that canister by your carb contains charcoal to keep your brake booster from dissolving from gas/oil fumes. It needs to be mounted vertically, as shown in @lars' diagram. Yours appears to be mounted backwards. I'd replace it, as the carbon has likely been sucked into your engine.
Here's a similar thread, with photos, including a cutaway of the filter.
There is no leaking fluid anywhere, the reservoir stays full.
Ok,
Going back to post 8.
New master. Bench bled.
By any chance did you shove the masters piston in more than 1 & 3/8 inches?
Could have damaged the piston rings or "O" rings.
Brake-fluid will seep past the seals and the Rez stays full.
But the braking never feels right in this scenario.
Click on my avatar on the left.
Look for photo albums, bench bleeding.
From: At my Bar drinking and wrenching in Lafayette Colorado
Originally Posted by ghosttoast
Right now, with the engine off, the pedal pumps up if I push it 3 times, but goes down if I keep my foot on it.
That's a sign of a master cylinder that is leaking internally. Just because you replaced the cylinder doesn't mean you got a good one. If the pedal goes down while maintaining modest pressure on it, the seals in the cylinder are leaking internally. That will not produce a visible external leak.
Ok, I bled and bled the brakes and the pedal is rock hard as it should be. I found no evidence of leaking fluid, but I did notice that this is the third time I have done this and every time there is air in the driver side front caliper. I guess I will wait and see if it goes soft on me again next time I take it for a longer drive. From all of my reading on this forum, I either haven't bled them enough, or rotor runout is causing that caliper to suck air, does that sound right?
